Stop ignoring DEBUGCTL[5:2] on AMD CPUs and instead treat them as reserved.
KVM has never properly virtualized AMD's legacy PBi bits, but did allow
the guest (and host userspace) to set the bits. To avoid breaking guests
when running on CPUs with BusLockTrap, which redefined bit 2 to BLCKDB and
made bits 5:3 reserved, a previous KVM change ignored bits 5:3, e.g. so
that legacy guest software wouldn't inadvertently enable BusLockTrap or
hit a VMRUN failure due to setting reserved.
To allow for virtualizing BusLockTrap and whatever future features may use
bits 5:3, treat bits 5:2 as reserved (and hope that doing so doesn't break
any existing guests).
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
When retpoline is enabled, indirect function calls introduce additional
performance overhead. Avoid frequent indirect calls to VMGEXIT when SEV
is enabled.
Signed-off-by: Peng Hao <flyingpeng@tencent.com>
Link: https://lore.kernel.org/r/20250306075425.66693-1-flyingpeng@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
AMD EPYC 5th generation processors have introduced a feature that allows
the hypervisor to control the SEV_FEATURES that are set for, or by, a
guest [1]. ALLOWED_SEV_FEATURES can be used by the hypervisor to enforce
that SEV-ES and SEV-SNP guests cannot enable features that the
hypervisor does not want to be enabled.
Always enable ALLOWED_SEV_FEATURES. A VMRUN will fail if any
non-reserved bits are 1 in SEV_FEATURES but are 0 in
ALLOWED_SEV_FEATURES.
Some SEV_FEATURES - currently PmcVirtualization and SecureAvic
(see Appendix B, Table B-4) - require an opt-in via ALLOWED_SEV_FEATURES,
i.e. are off-by-default, whereas all other features are effectively
on-by-default, but still honor ALLOWED_SEV_FEATURES.
[1] Section 15.36.20 "Allowed SEV Features", AMD64 Architecture
Programmer's Manual, Pub. 24593 Rev. 3.42 - March 2024:
https://bugzilla.kernel.org/attachment.cgi?id=306250
Co-developed-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20250310201603.1217954-3-kim.phillips@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
If multiple VMRUN instructions fail, resulting in calls to dump_vmcb(),
the output can become interleaved and it is impossible to identify which
line of output belongs to which VMCB. Add a mutex to dump_vmcb() so that
the output is serialized.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Link: https://lore.kernel.org/r/a880678afd9488e1dd6017445802712f7c02cc6d.1742477213.git.thomas.lendacky@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
An SEV-ES/SEV-SNP VM save area (VMSA) can be decrypted if the guest
policy allows debugging. Update the dump_vmcb() routine to output
some of the SEV VMSA contents if possible. This can be useful for
debug purposes.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Link: https://lore.kernel.org/r/ea3b852c295b6f4b200925ed6b6e2c90d9475e71.1742477213.git.thomas.lendacky@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add a module param to each KVM vendor module to allow disabling device
posted interrupts without having to sacrifice all of APICv/AVIC, and to
also effectively enumerate to userspace whether or not KVM may be
utilizing device posted IRQs. Disabling device posted interrupts is
very desirable for testing, and can even be desirable for production
environments, e.g. if the host kernel wants to interpose on device
interrupts.
Put the module param in kvm-{amd,intel}.ko instead of kvm.ko to match
the overall APICv/AVIC controls, and to avoid complications with said
controls. E.g. if the param is in kvm.ko, KVM needs to be snapshot the
original user-defined value to play nice with a vendor module being
reloaded with different enable_apicv settings.
Link: https://lore.kernel.org/r/20250401161804.842968-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Previously, commit ed129ec905 ("KVM: x86: forcibly leave nested mode
on vCPU reset") addressed an issue where a triple fault occurring in
nested mode could lead to use-after-free scenarios. However, the commit
did not handle the analogous situation for System Management Mode (SMM).
This omission results in triggering a WARN when KVM forces a vCPU INIT
after SHUTDOWN interception while the vCPU is in SMM. This situation was
reprodused using Syzkaller by:
1) Creating a KVM VM and vCPU
2) Sending a KVM_SMI ioctl to explicitly enter SMM
3) Executing invalid instructions causing consecutive exceptions and
eventually a triple fault
The issue manifests as follows:
WARNING: CPU: 0 PID: 25506 at arch/x86/kvm/x86.c:12112
kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112
Modules linked in:
CPU: 0 PID: 25506 Comm: syz-executor.0 Not tainted
6.1.130-syzkaller-00157-g164fe5dde9b6 #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.12.0-1 04/01/2014
RIP: 0010:kvm_vcpu_reset+0x1d2/0x1530 arch/x86/kvm/x86.c:12112
Call Trace:
<TASK>
shutdown_interception+0x66/0xb0 arch/x86/kvm/svm/svm.c:2136
svm_invoke_exit_handler+0x110/0x530 arch/x86/kvm/svm/svm.c:3395
svm_handle_exit+0x424/0x920 arch/x86/kvm/svm/svm.c:3457
vcpu_enter_guest arch/x86/kvm/x86.c:10959 [inline]
vcpu_run+0x2c43/0x5a90 arch/x86/kvm/x86.c:11062
kvm_arch_vcpu_ioctl_run+0x50f/0x1cf0 arch/x86/kvm/x86.c:11283
kvm_vcpu_ioctl+0x570/0xf00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4122
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x19a/0x210 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
Architecturally, INIT is blocked when the CPU is in SMM, hence KVM's WARN()
in kvm_vcpu_reset() to guard against KVM bugs, e.g. to detect improper
emulation of INIT. SHUTDOWN on SVM is a weird edge case where KVM needs to
do _something_ sane with the VMCB, since it's technically undefined, and
INIT is the least awful choice given KVM's ABI.
So, double down on stuffing INIT on SHUTDOWN, and force the vCPU out of
SMM to avoid any weirdness (and the WARN).
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: ed129ec905 ("KVM: x86: forcibly leave nested mode on vCPU reset")
Cc: stable@vger.kernel.org
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mikhail Lobanov <m.lobanov@rosa.ru>
Link: https://lore.kernel.org/r/20250414171207.155121-1-m.lobanov@rosa.ru
[sean: massage changelog, make it clear this isn't architectural behavior]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This large commit contains the initial support for TDX in KVM. All x86
parts enable the host-side hypercalls that KVM uses to talk to the TDX
module, a software component that runs in a special CPU mode called SEAM
(Secure Arbitration Mode).
The series is in turn split into multiple sub-series, each with a separate
merge commit:
- Initialization: basic setup for using the TDX module from KVM, plus
ioctls to create TDX VMs and vCPUs.
- MMU: in TDX, private and shared halves of the address space are mapped by
different EPT roots, and the private half is managed by the TDX module.
Using the support that was added to the generic MMU code in 6.14,
add support for TDX's secure page tables to the Intel side of KVM.
Generic KVM code takes care of maintaining a mirror of the secure page
tables so that they can be queried efficiently, and ensuring that changes
are applied to both the mirror and the secure EPT.
- vCPU enter/exit: implement the callbacks that handle the entry of a TDX
vCPU (via the SEAMCALL TDH.VP.ENTER) and the corresponding save/restore
of host state.
- Userspace exits: introduce support for guest TDVMCALLs that KVM forwards to
userspace. These correspond to the usual KVM_EXIT_* "heavyweight vmexits"
but are triggered through a different mechanism, similar to VMGEXIT for
SEV-ES and SEV-SNP.
- Interrupt handling: support for virtual interrupt injection as well as
handling VM-Exits that are caused by vectored events. Exclusive to
TDX are machine-check SMIs, which the kernel already knows how to
handle through the kernel machine check handler (commit 7911f145de,
"x86/mce: Implement recovery for errors in TDX/SEAM non-root mode")
- Loose ends: handling of the remaining exits from the TDX module, including
EPT violation/misconfig and several TDVMCALL leaves that are handled in
the kernel (CPUID, HLT, RDMSR/WRMSR, GetTdVmCallInfo); plus returning
an error or ignoring operations that are not supported by TDX guests
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* Nested virtualization support for VGICv3, giving the nested
hypervisor control of the VGIC hardware when running an L2 VM
* Removal of 'late' nested virtualization feature register masking,
making the supported feature set directly visible to userspace
* Support for emulating FEAT_PMUv3 on Apple silicon, taking advantage
of an IMPLEMENTATION DEFINED trap that covers all PMUv3 registers
* Paravirtual interface for discovering the set of CPU implementations
where a VM may run, addressing a longstanding issue of guest CPU
errata awareness in big-little systems and cross-implementation VM
migration
* Userspace control of the registers responsible for identifying a
particular CPU implementation (MIDR_EL1, REVIDR_EL1, AIDR_EL1),
allowing VMs to be migrated cross-implementation
* pKVM updates, including support for tracking stage-2 page table
allocations in the protected hypervisor in the 'SecPageTable' stat
* Fixes to vPMU, ensuring that userspace updates to the vPMU after
KVM_RUN are reflected into the backing perf events
LoongArch:
* Remove unnecessary header include path
* Assume constant PGD during VM context switch
* Add perf events support for guest VM
RISC-V:
* Disable the kernel perf counter during configure
* KVM selftests improvements for PMU
* Fix warning at the time of KVM module removal
x86:
* Add support for aging of SPTEs without holding mmu_lock. Not taking mmu_lock
allows multiple aging actions to run in parallel, and more importantly avoids
stalling vCPUs. This includes an implementation of per-rmap-entry locking;
aging the gfn is done with only a per-rmap single-bin spinlock taken, whereas
locking an rmap for write requires taking both the per-rmap spinlock and
the mmu_lock.
Note that this decreases slightly the accuracy of accessed-page information,
because changes to the SPTE outside aging might not use atomic operations
even if they could race against a clear of the Accessed bit. This is
deliberate because KVM and mm/ tolerate false positives/negatives for
accessed information, and testing has shown that reducing the latency of
aging is far more beneficial to overall system performance than providing
"perfect" young/old information.
* Defer runtime CPUID updates until KVM emulates a CPUID instruction, to
coalesce updates when multiple pieces of vCPU state are changing, e.g. as
part of a nested transition.
* Fix a variety of nested emulation bugs, and add VMX support for synthesizing
nested VM-Exit on interception (instead of injecting #UD into L2).
* Drop "support" for async page faults for protected guests that do not set
SEND_ALWAYS (i.e. that only want async page faults at CPL3)
* Bring a bit of sanity to x86's VM teardown code, which has accumulated
a lot of cruft over the years. Particularly, destroy vCPUs before
the MMU, despite the latter being a VM-wide operation.
* Add common secure TSC infrastructure for use within SNP and in the
future TDX
* Block KVM_CAP_SYNC_REGS if guest state is protected. It does not make
sense to use the capability if the relevant registers are not
available for reading or writing.
* Don't take kvm->lock when iterating over vCPUs in the suspend notifier to
fix a largely theoretical deadlock.
* Use the vCPU's actual Xen PV clock information when starting the Xen timer,
as the cached state in arch.hv_clock can be stale/bogus.
* Fix a bug where KVM could bleed PVCLOCK_GUEST_STOPPED across different
PV clocks; restrict PVCLOCK_GUEST_STOPPED to kvmclock, as KVM's suspend
notifier only accounts for kvmclock, and there's no evidence that the
flag is actually supported by Xen guests.
* Clean up the per-vCPU "cache" of its reference pvclock, and instead only
track the vCPU's TSC scaling (multipler+shift) metadata (which is moderately
expensive to compute, and rarely changes for modern setups).
* Don't write to the Xen hypercall page on MSR writes that are initiated by
the host (userspace or KVM) to fix a class of bugs where KVM can write to
guest memory at unexpected times, e.g. during vCPU creation if userspace has
set the Xen hypercall MSR index to collide with an MSR that KVM emulates.
* Restrict the Xen hypercall MSR index to the unofficial synthetic range to
reduce the set of possible collisions with MSRs that are emulated by KVM
(collisions can still happen as KVM emulates Hyper-V MSRs, which also reside
in the synthetic range).
* Clean up and optimize KVM's handling of Xen MSR writes and xen_hvm_config.
* Update Xen TSC leaves during CPUID emulation instead of modifying the CPUID
entries when updating PV clocks; there is no guarantee PV clocks will be
updated between TSC frequency changes and CPUID emulation, and guest reads
of the TSC leaves should be rare, i.e. are not a hot path.
x86 (Intel):
* Fix a bug where KVM unnecessarily reads XFD_ERR from hardware and thus
modifies the vCPU's XFD_ERR on a #NM due to CR0.TS=1.
* Pass XFD_ERR as the payload when injecting #NM, as a preparatory step
for upcoming FRED virtualization support.
* Decouple the EPT entry RWX protection bit macros from the EPT Violation
bits, both as a general cleanup and in anticipation of adding support for
emulating Mode-Based Execution Control (MBEC).
* Reject KVM_RUN if userspace manages to gain control and stuff invalid guest
state while KVM is in the middle of emulating nested VM-Enter.
* Add a macro to handle KVM's sanity checks on entry/exit VMCS control pairs
in anticipation of adding sanity checks for secondary exit controls (the
primary field is out of bits).
x86 (AMD):
* Ensure the PSP driver is initialized when both the PSP and KVM modules are
built-in (the initcall framework doesn't handle dependencies).
* Use long-term pins when registering encrypted memory regions, so that the
pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and don't lead to
excessive fragmentation.
* Add macros and helpers for setting GHCB return/error codes.
* Add support for Idle HLT interception, which elides interception if the vCPU
has a pending, unmasked virtual IRQ when HLT is executed.
* Fix a bug in INVPCID emulation where KVM fails to check for a non-canonical
address.
* Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is invalid, e.g.
because the vCPU was "destroyed" via SNP's AP Creation hypercall.
* Reject SNP AP Creation if the requested SEV features for the vCPU don't
match the VM's configured set of features.
Selftests:
* Fix again the Intel PMU counters test; add a data load and do CLFLUSH{OPT} on the data
instead of executing code. The theory is that modern Intel CPUs have
learned new code prefetching tricks that bypass the PMU counters.
* Fix a flaw in the Intel PMU counters test where it asserts that an event is
counting correctly without actually knowing what the event counts on the
underlying hardware.
* Fix a variety of flaws, bugs, and false failures/passes dirty_log_test, and
improve its coverage by collecting all dirty entries on each iteration.
* Fix a few minor bugs related to handling of stats FDs.
* Add infrastructure to make vCPU and VM stats FDs available to tests by
default (open the FDs during VM/vCPU creation).
* Relax an assertion on the number of HLT exits in the xAPIC IPI test when
running on a CPU that supports AMD's Idle HLT (which elides interception of
HLT if a virtual IRQ is pending and unmasked).
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm updates from Paolo Bonzini:
"ARM:
- Nested virtualization support for VGICv3, giving the nested
hypervisor control of the VGIC hardware when running an L2 VM
- Removal of 'late' nested virtualization feature register masking,
making the supported feature set directly visible to userspace
- Support for emulating FEAT_PMUv3 on Apple silicon, taking advantage
of an IMPLEMENTATION DEFINED trap that covers all PMUv3 registers
- Paravirtual interface for discovering the set of CPU
implementations where a VM may run, addressing a longstanding issue
of guest CPU errata awareness in big-little systems and
cross-implementation VM migration
- Userspace control of the registers responsible for identifying a
particular CPU implementation (MIDR_EL1, REVIDR_EL1, AIDR_EL1),
allowing VMs to be migrated cross-implementation
- pKVM updates, including support for tracking stage-2 page table
allocations in the protected hypervisor in the 'SecPageTable' stat
- Fixes to vPMU, ensuring that userspace updates to the vPMU after
KVM_RUN are reflected into the backing perf events
LoongArch:
- Remove unnecessary header include path
- Assume constant PGD during VM context switch
- Add perf events support for guest VM
RISC-V:
- Disable the kernel perf counter during configure
- KVM selftests improvements for PMU
- Fix warning at the time of KVM module removal
x86:
- Add support for aging of SPTEs without holding mmu_lock.
Not taking mmu_lock allows multiple aging actions to run in
parallel, and more importantly avoids stalling vCPUs. This includes
an implementation of per-rmap-entry locking; aging the gfn is done
with only a per-rmap single-bin spinlock taken, whereas locking an
rmap for write requires taking both the per-rmap spinlock and the
mmu_lock.
Note that this decreases slightly the accuracy of accessed-page
information, because changes to the SPTE outside aging might not
use atomic operations even if they could race against a clear of
the Accessed bit.
This is deliberate because KVM and mm/ tolerate false
positives/negatives for accessed information, and testing has shown
that reducing the latency of aging is far more beneficial to
overall system performance than providing "perfect" young/old
information.
- Defer runtime CPUID updates until KVM emulates a CPUID instruction,
to coalesce updates when multiple pieces of vCPU state are
changing, e.g. as part of a nested transition
- Fix a variety of nested emulation bugs, and add VMX support for
synthesizing nested VM-Exit on interception (instead of injecting
#UD into L2)
- Drop "support" for async page faults for protected guests that do
not set SEND_ALWAYS (i.e. that only want async page faults at CPL3)
- Bring a bit of sanity to x86's VM teardown code, which has
accumulated a lot of cruft over the years. Particularly, destroy
vCPUs before the MMU, despite the latter being a VM-wide operation
- Add common secure TSC infrastructure for use within SNP and in the
future TDX
- Block KVM_CAP_SYNC_REGS if guest state is protected. It does not
make sense to use the capability if the relevant registers are not
available for reading or writing
- Don't take kvm->lock when iterating over vCPUs in the suspend
notifier to fix a largely theoretical deadlock
- Use the vCPU's actual Xen PV clock information when starting the
Xen timer, as the cached state in arch.hv_clock can be stale/bogus
- Fix a bug where KVM could bleed PVCLOCK_GUEST_STOPPED across
different PV clocks; restrict PVCLOCK_GUEST_STOPPED to kvmclock, as
KVM's suspend notifier only accounts for kvmclock, and there's no
evidence that the flag is actually supported by Xen guests
- Clean up the per-vCPU "cache" of its reference pvclock, and instead
only track the vCPU's TSC scaling (multipler+shift) metadata (which
is moderately expensive to compute, and rarely changes for modern
setups)
- Don't write to the Xen hypercall page on MSR writes that are
initiated by the host (userspace or KVM) to fix a class of bugs
where KVM can write to guest memory at unexpected times, e.g.
during vCPU creation if userspace has set the Xen hypercall MSR
index to collide with an MSR that KVM emulates
- Restrict the Xen hypercall MSR index to the unofficial synthetic
range to reduce the set of possible collisions with MSRs that are
emulated by KVM (collisions can still happen as KVM emulates
Hyper-V MSRs, which also reside in the synthetic range)
- Clean up and optimize KVM's handling of Xen MSR writes and
xen_hvm_config
- Update Xen TSC leaves during CPUID emulation instead of modifying
the CPUID entries when updating PV clocks; there is no guarantee PV
clocks will be updated between TSC frequency changes and CPUID
emulation, and guest reads of the TSC leaves should be rare, i.e.
are not a hot path
x86 (Intel):
- Fix a bug where KVM unnecessarily reads XFD_ERR from hardware and
thus modifies the vCPU's XFD_ERR on a #NM due to CR0.TS=1
- Pass XFD_ERR as the payload when injecting #NM, as a preparatory
step for upcoming FRED virtualization support
- Decouple the EPT entry RWX protection bit macros from the EPT
Violation bits, both as a general cleanup and in anticipation of
adding support for emulating Mode-Based Execution Control (MBEC)
- Reject KVM_RUN if userspace manages to gain control and stuff
invalid guest state while KVM is in the middle of emulating nested
VM-Enter
- Add a macro to handle KVM's sanity checks on entry/exit VMCS
control pairs in anticipation of adding sanity checks for secondary
exit controls (the primary field is out of bits)
x86 (AMD):
- Ensure the PSP driver is initialized when both the PSP and KVM
modules are built-in (the initcall framework doesn't handle
dependencies)
- Use long-term pins when registering encrypted memory regions, so
that the pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and
don't lead to excessive fragmentation
- Add macros and helpers for setting GHCB return/error codes
- Add support for Idle HLT interception, which elides interception if
the vCPU has a pending, unmasked virtual IRQ when HLT is executed
- Fix a bug in INVPCID emulation where KVM fails to check for a
non-canonical address
- Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is
invalid, e.g. because the vCPU was "destroyed" via SNP's AP
Creation hypercall
- Reject SNP AP Creation if the requested SEV features for the vCPU
don't match the VM's configured set of features
Selftests:
- Fix again the Intel PMU counters test; add a data load and do
CLFLUSH{OPT} on the data instead of executing code. The theory is
that modern Intel CPUs have learned new code prefetching tricks
that bypass the PMU counters
- Fix a flaw in the Intel PMU counters test where it asserts that an
event is counting correctly without actually knowing what the event
counts on the underlying hardware
- Fix a variety of flaws, bugs, and false failures/passes
dirty_log_test, and improve its coverage by collecting all dirty
entries on each iteration
- Fix a few minor bugs related to handling of stats FDs
- Add infrastructure to make vCPU and VM stats FDs available to tests
by default (open the FDs during VM/vCPU creation)
- Relax an assertion on the number of HLT exits in the xAPIC IPI test
when running on a CPU that supports AMD's Idle HLT (which elides
interception of HLT if a virtual IRQ is pending and unmasked)"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (216 commits)
RISC-V: KVM: Optimize comments in kvm_riscv_vcpu_isa_disable_allowed
RISC-V: KVM: Teardown riscv specific bits after kvm_exit
LoongArch: KVM: Register perf callbacks for guest
LoongArch: KVM: Implement arch-specific functions for guest perf
LoongArch: KVM: Add stub for kvm_arch_vcpu_preempted_in_kernel()
LoongArch: KVM: Remove PGD saving during VM context switch
LoongArch: KVM: Remove unnecessary header include path
KVM: arm64: Tear down vGIC on failed vCPU creation
KVM: arm64: PMU: Reload when resetting
KVM: arm64: PMU: Reload when user modifies registers
KVM: arm64: PMU: Fix SET_ONE_REG for vPMC regs
KVM: arm64: PMU: Assume PMU presence in pmu-emul.c
KVM: arm64: PMU: Set raw values from user to PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR}
KVM: arm64: Create each pKVM hyp vcpu after its corresponding host vcpu
KVM: arm64: Factor out pKVM hyp vcpu creation to separate function
KVM: arm64: Initialize HCRX_EL2 traps in pKVM
KVM: arm64: Factor out setting HCRX_EL2 traps into separate function
KVM: x86: block KVM_CAP_SYNC_REGS if guest state is protected
KVM: x86: Add infrastructure for secure TSC
KVM: x86: Push down setting vcpu.arch.user_set_tsc
...
attack vectors instead of single vulnerabilities
- Untangle and remove a now unneeded X86_FEATURE_USE_IBPB flag
- Add support for a Zen5-specific SRSO mitigation
- Cleanups and minor improvements
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Merge tag 'x86_bugs_for_v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 speculation mitigation updates from Borislav Petkov:
- Some preparatory work to convert the mitigations machinery to
mitigating attack vectors instead of single vulnerabilities
- Untangle and remove a now unneeded X86_FEATURE_USE_IBPB flag
- Add support for a Zen5-specific SRSO mitigation
- Cleanups and minor improvements
* tag 'x86_bugs_for_v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/bugs: Make spectre user default depend on MITIGATION_SPECTRE_V2
x86/bugs: Use the cpu_smt_possible() helper instead of open-coded code
x86/bugs: Add AUTO mitigations for mds/taa/mmio/rfds
x86/bugs: Relocate mds/taa/mmio/rfds defines
x86/bugs: Add X86_BUG_SPECTRE_V2_USER
x86/bugs: Remove X86_FEATURE_USE_IBPB
KVM: nVMX: Always use IBPB to properly virtualize IBRS
x86/bugs: Use a static branch to guard IBPB on vCPU switch
x86/bugs: Remove the X86_FEATURE_USE_IBPB check in ib_prctl_set()
x86/mm: Remove X86_FEATURE_USE_IBPB checks in cond_mitigation()
x86/bugs: Move the X86_FEATURE_USE_IBPB check into callers
x86/bugs: KVM: Add support for SRSO_MSR_FIX
- Ensure the PSP driver is initialized when both the PSP and KVM modules are
built-in (the initcall framework doesn't handle dependencies).
- Use long-term pins when registering encrypted memory regions, so that the
pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and don't lead to
excessive fragmentation.
- Add macros and helpers for setting GHCB return/error codes.
- Add support for Idle HLT interception, which elides interception if the vCPU
has a pending, unmasked virtual IRQ when HLT is executed.
- Fix a bug in INVPCID emulation where KVM fails to check for a non-canonical
address.
- Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is invalid, e.g.
because the vCPU was "destroyed" via SNP's AP Creation hypercall.
- Reject SNP AP Creation if the requested SEV features for the vCPU don't
match the VM's configured set of features.
- Misc cleanups
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Merge tag 'kvm-x86-svm-6.15' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.15
- Ensure the PSP driver is initialized when both the PSP and KVM modules are
built-in (the initcall framework doesn't handle dependencies).
- Use long-term pins when registering encrypted memory regions, so that the
pages are migrated out of MIGRATE_CMA/ZONE_MOVABLE and don't lead to
excessive fragmentation.
- Add macros and helpers for setting GHCB return/error codes.
- Add support for Idle HLT interception, which elides interception if the vCPU
has a pending, unmasked virtual IRQ when HLT is executed.
- Fix a bug in INVPCID emulation where KVM fails to check for a non-canonical
address.
- Don't attempt VMRUN for SEV-ES+ guests if the vCPU's VMSA is invalid, e.g.
because the vCPU was "destroyed" via SNP's AP Creation hypercall.
- Reject SNP AP Creation if the requested SEV features for the vCPU don't
match the VM's configured set of features.
- Misc cleanups
- Fix a bug in PIC emulation that caused KVM to emit a spurious KVM_REQ_EVENT.
- Add a helper to consolidate handling of mp_state transitions, and use it to
clear pv_unhalted whenever a vCPU is made RUNNABLE.
- Defer runtime CPUID updates until KVM emulates a CPUID instruction, to
coalesce updates when multiple pieces of vCPU state are changing, e.g. as
part of a nested transition.
- Fix a variety of nested emulation bugs, and add VMX support for synthesizing
nested VM-Exit on interception (instead of injecting #UD into L2).
- Drop "support" for PV Async #PF with proctected guests without SEND_ALWAYS,
as KVM can't get the current CPL.
- Misc cleanups
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Merge tag 'kvm-x86-misc-6.15' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.15:
- Fix a bug in PIC emulation that caused KVM to emit a spurious KVM_REQ_EVENT.
- Add a helper to consolidate handling of mp_state transitions, and use it to
clear pv_unhalted whenever a vCPU is made RUNNABLE.
- Defer runtime CPUID updates until KVM emulates a CPUID instruction, to
coalesce updates when multiple pieces of vCPU state are changing, e.g. as
part of a nested transition.
- Fix a variety of nested emulation bugs, and add VMX support for synthesizing
nested VM-Exit on interception (instead of injecting #UD into L2).
- Drop "support" for PV Async #PF with proctected guests without SEND_ALWAYS,
as KVM can't get the current CPL.
- Misc cleanups
In some cases, the handling of quirks is split between platform-specific
code and generic code, or it is done entirely in generic code, but the
relevant bug does not trigger on some platforms; for example,
this will be the case for "ignore guest PAT". Allow unaffected vendor
modules to disable handling of a quirk for all VMs via a new entry in
kvm_caps.
Such quirks remain available in KVM_CAP_DISABLE_QUIRKS2, because that API
tells userspace that KVM *knows* that some of its past behavior was bogus
or just undesirable. In other words, it's plausible for userspace to
refuse to run if a quirk is not listed by KVM_CAP_DISABLE_QUIRKS2, so
preserve that and make it part of the API.
As an example, mark KVM_X86_QUIRK_CD_NW_CLEARED as auto-disabled on
Intel systems.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Explicitly reject KVM_RUN with KVM_EXIT_FAIL_ENTRY if userspace "coerces"
KVM into running an SEV-ES+ guest with an invalid VMSA, e.g. by modifying
a vCPU's mp_state to be RUNNABLE after an SNP vCPU has undergone a Destroy
event. On Destroy or failed Create, KVM marks the vCPU HALTED so that
*KVM* doesn't run the vCPU, but nothing prevents a misbehaving VMM from
manually making the vCPU RUNNABLE via KVM_SET_MP_STATE.
Attempting VMRUN with an invalid VMSA should be harmless, but knowingly
executing VMRUN with bad control state is at best dodgy.
Fixes: e366f92ea9 ("KVM: SEV: Support SEV-SNP AP Creation NAE event")
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20250227012541.3234589-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Manually load the guest's DEBUGCTL prior to VMRUN (and restore the host's
value on #VMEXIT) if it diverges from the host's value and LBR
virtualization is disabled, as hardware only context switches DEBUGCTL if
LBR virtualization is fully enabled. Running the guest with the host's
value has likely been mildly problematic for quite some time, e.g. it will
result in undesirable behavior if BTF diverges (with the caveat that KVM
now suppresses guest BTF due to lack of support).
But the bug became fatal with the introduction of Bus Lock Trap ("Detect"
in kernel paralance) support for AMD (commit 408eb7417a
("x86/bus_lock: Add support for AMD")), as a bus lock in the guest will
trigger an unexpected #DB.
Note, suppressing the bus lock #DB, i.e. simply resuming the guest without
injecting a #DB, is not an option. It wouldn't address the general issue
with DEBUGCTL, e.g. for things like BTF, and there are other guest-visible
side effects if BusLockTrap is left enabled.
If BusLockTrap is disabled, then DR6.BLD is reserved-to-1; any attempts to
clear it by software are ignored. But if BusLockTrap is enabled, software
can clear DR6.BLD:
Software enables bus lock trap by setting DebugCtl MSR[BLCKDB] (bit 2)
to 1. When bus lock trap is enabled, ... The processor indicates that
this #DB was caused by a bus lock by clearing DR6[BLD] (bit 11). DR6[11]
previously had been defined to be always 1.
and clearing DR6.BLD is "sticky" in that it's not set (i.e. lowered) by
other #DBs:
All other #DB exceptions leave DR6[BLD] unmodified
E.g. leaving BusLockTrap enable can confuse a legacy guest that writes '0'
to reset DR6.
Reported-by: rangemachine@gmail.com
Reported-by: whanos@sergal.fun
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219787
Closes: https://lore.kernel.org/all/bug-219787-28872@https.bugzilla.kernel.org%2F
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Mark BTF as reserved in DEBUGCTL on AMD, as KVM doesn't actually support
BTF, and fully enabling BTF virtualization is non-trivial due to
interactions with the emulator, guest_debug, #DB interception, nested SVM,
etc.
Don't inject #GP if the guest attempts to set BTF, as there's no way to
communicate lack of support to the guest, and instead suppress the flag
and treat the WRMSR as (partially) unsupported.
In short, make KVM behave the same on AMD and Intel (VMX already squashes
BTF).
Note, due to other bugs in KVM's handling of DEBUGCTL, the only way BTF
has "worked" in any capacity is if the guest simultaneously enables LBRs.
Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop bits 5:2 from the guest's effective DEBUGCTL value, as AMD changed
the architectural behavior of the bits and broke backwards compatibility.
On CPUs without BusLockTrap (or at least, in APMs from before ~2023),
bits 5:2 controlled the behavior of external pins:
Performance-Monitoring/Breakpoint Pin-Control (PBi)—Bits 5:2, read/write.
Software uses thesebits to control the type of information reported by
the four external performance-monitoring/breakpoint pins on the
processor. When a PBi bit is cleared to 0, the corresponding external pin
(BPi) reports performance-monitor information. When a PBi bit is set to
1, the corresponding external pin (BPi) reports breakpoint information.
With the introduction of BusLockTrap, presumably to be compatible with
Intel CPUs, AMD redefined bit 2 to be BLCKDB:
Bus Lock #DB Trap (BLCKDB)—Bit 2, read/write. Software sets this bit to
enable generation of a #DB trap following successful execution of a bus
lock when CPL is > 0.
and redefined bits 5:3 (and bit 6) as "6:3 Reserved MBZ".
Ideally, KVM would treat bits 5:2 as reserved. Defer that change to a
feature cleanup to avoid breaking existing guest in LTS kernels. For now,
drop the bits to retain backwards compatibility (of a sort).
Note, dropping bits 5:2 is still a guest-visible change, e.g. if the guest
is enabling LBRs *and* the legacy PBi bits, then the state of the PBi bits
is visible to the guest, whereas now the guest will always see '0'.
Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Inject a #GP if the memory operand received by INVCPID is non-canonical.
The APM clearly states that the intercept takes priority over all #GP
checks except the CPL0 restriction.
Of course, that begs the question of how the CPU generates a linear
address in the first place. Tracing confirms that EXITINFO1 does hold a
linear address, at least for 64-bit mode guests (hooray GS prefix).
Unfortunately, the APM says absolutely nothing about the EXITINFO fields
for INVPCID intercepts, so it's not at all clear what's supposed to
happen.
Add a FIXME to call out that KVM still does the wrong thing for 32-bit
guests, and if the stack segment is used for the memory operand.
Cc: Babu Moger <babu.moger@amd.com>
Cc: Jim Mattson <jmattson@google.com>
Fixes: 4407a797e9 ("KVM: SVM: Enable INVPCID feature on AMD")
Link: https://lore.kernel.org/r/20250224174522.2363400-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Enable/disable local IRQs, i.e. set/clear RFLAGS.IF, in the common
svm_vcpu_enter_exit() just after/before guest_state_{enter,exit}_irqoff()
so that VMRUN is not executed in an STI shadow. AMD CPUs have a quirk
(some would say "bug"), where the STI shadow bleeds into the guest's
intr_state field if a #VMEXIT occurs during injection of an event, i.e. if
the VMRUN doesn't complete before the subsequent #VMEXIT.
The spurious "interrupts masked" state is relatively benign, as it only
occurs during event injection and is transient. Because KVM is already
injecting an event, the guest can't be in HLT, and if KVM is querying IRQ
blocking for injection, then KVM would need to force an immediate exit
anyways since injecting multiple events is impossible.
However, because KVM copies int_state verbatim from vmcb02 to vmcb12, the
spurious STI shadow is visible to L1 when running a nested VM, which can
trip sanity checks, e.g. in VMware's VMM.
Hoist the STI+CLI all the way to C code, as the aforementioned calls to
guest_state_{enter,exit}_irqoff() already inform lockdep that IRQs are
enabled/disabled, and taking a fault on VMRUN with RFLAGS.IF=1 is already
possible. I.e. if there's kernel code that is confused by running with
RFLAGS.IF=1, then it's already a problem. In practice, since GIF=0 also
blocks NMIs, the only change in exposure to non-KVM code (relative to
surrounding VMRUN with STI+CLI) is exception handling code, and except for
the kvm_rebooting=1 case, all exception in the core VM-Enter/VM-Exit path
are fatal.
Use the "raw" variants to enable/disable IRQs to avoid tracing in the
"no instrumentation" code; the guest state helpers also take care of
tracing IRQ state.
Oppurtunstically document why KVM needs to do STI in the first place.
Reported-by: Doug Covelli <doug.covelli@broadcom.com>
Closes: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4uzJQ@mail.gmail.com
Fixes: f14eec0a32 ("KVM: SVM: move more vmentry code to assembly")
Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20250224165442.2338294-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Instead of using X86_FEATURE_USE_IBPB to guard the IBPB execution in KVM
when a new vCPU is loaded, introduce a static branch, similar to
switch_mm_*_ibpb.
This makes it obvious in spectre_v2_user_select_mitigation() what
exactly is being toggled, instead of the unclear X86_FEATURE_USE_IBPB
(which will be shortly removed). It also provides more fine-grained
control, making it simpler to change/add paths that control the IBPB in
the vCPU switch path without affecting other IBPBs.
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20250227012712.3193063-5-yosry.ahmed@linux.dev
indirect_branch_prediction_barrier() only performs the MSR write if
X86_FEATURE_USE_IBPB is set, using alternative_msr_write(). In
preparation for removing X86_FEATURE_USE_IBPB, move the feature check
into the callers so that they can be addressed one-by-one, and use
X86_FEATURE_IBPB instead to guard the MSR write.
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20250227012712.3193063-2-yosry.ahmed@linux.dev
Add support for
CPUID Fn8000_0021_EAX[31] (SRSO_MSR_FIX). If this bit is 1, it
indicates that software may use MSR BP_CFG[BpSpecReduce] to mitigate
SRSO.
Enable BpSpecReduce to mitigate SRSO across guest/host boundaries.
Switch back to enabling the bit when virtualization is enabled and to
clear the bit when virtualization is disabled because using a MSR slot
would clear the bit when the guest is exited and any training the guest
has done, would potentially influence the host kernel when execution
enters the kernel and hasn't VMRUN the guest yet.
More detail on the public thread in Link below.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241202120416.6054-1-bp@kernel.org
Add support for "Idle HLT" interception on AMD CPUs, and enable Idle HLT
interception instead of "normal" HLT interception for all VMs for which
HLT-exiting is enabled. Idle HLT provides a mild performance boost for
all VM types, by avoiding a VM-Exit in the scenario where KVM would
immediately "wake" and resume the vCPU.
Idle HLT makes HLT-exiting conditional on the vCPU not having a valid,
unmasked interrupt. Specifically, a VM-Exit occurs on execution of HLT
if and only if there are no pending V_IRQ or V_NMI events. Note, Idle
is a replacement for full HLT interception, i.e. enabling HLT interception
would result in all HLT instructions causing unconditional VM-Exits. Per
the APM:
When both HLT and Idle HLT intercepts are active at the same time, the
HLT intercept takes priority. This intercept occurs only if a virtual
interrupt is not pending (V_INTR or V_NMI).
For KVM's use of V_IRQ (also called V_INTR in the APM) to detect interrupt
windows, the net effect of enabling Idle HLT is that, if a virtual
interupt is pending and unmasked at the time of HLT, the vCPU will take
a V_IRQ intercept instead of a HLT intercept.
When AVIC is enabled, Idle HLT works as intended: the vCPU continues
unimpeded and services the pending virtual interrupt.
Note, the APM's description of V_IRQ interaction with AVIC is quite
confusing, and requires piecing together implied behavior. Per the APM,
when AVIC is enabled, V_IRQ *from the VMCB* is ignored:
When AVIC mode is enabled for a virtual processor, the V_IRQ, V_INTR_PRIO,
V_INTR_VECTOR, and V_IGN_TPR fields in the VMCB are ignored.
Which seems to contradict the behavior of Idle HLT:
This intercept occurs only if a virtual interrupt is not pending (V_INTR
or V_NMI).
What's not explicitly stated is that hardware's internal copy of V_IRQ
(and related fields) *are* still active, i.e. are presumably used to cache
information from the virtual APIC.
Handle Idle HLT exits as if they were normal HLT exits, e.g. don't try to
optimize the handling under the assumption that there isn't a pending IRQ.
Irrespective of AVIC, Idle HLT is inherently racy with respect to the vIRR,
as KVM can set vIRR bits asychronously.
No changes are required to support KVM's use Idle HLT while running
L2. In fact, supporting Idle HLT is actually a bug fix to some extent.
If L1 wants to intercept HLT, recalc_intercepts() will enable HLT
interception in vmcb02 and forward the intercept to L1 as normal.
But if L1 does not want to intercept HLT, then KVM will run L2 with Idle
HLT enabled and HLT interception disabled. If a V_IRQ or V_NMI for L2
becomes pending and L2 executes HLT, then use of Idle HLT will do the
right thing, i.e. not #VMEXIT and instead deliver the virtual event. KVM
currently doesn't handle this scenario correctly, e.g. doesn't check V_IRQ
or V_NMI in vmcs02 as part of kvm_vcpu_has_events().
Do not expose Idle HLT to L1 at this time, as supporting nested Idle HLT is
more complex than just enumerating the feature, e.g. requires KVM to handle
the aforementioned scenarios of V_IRQ and V_NMI at the time of exit.
Signed-off-by: Manali Shukla <Manali.Shukla@amd.com>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Link: https://bugzilla.kernel.org/attachment.cgi?id=306250
Link: https://lore.kernel.org/r/20250128124812.7324-3-manali.shukla@amd.com
[sean: rewrite changelog, drop nested "support"]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Provide helpers to set the error code when converting VMGEXIT SW_EXITINFO1 and
SW_EXITINFO2 codes from plain numbers to proper defines. Add comments for
better code readability.
No functionality changed.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Melody Wang <huibo.wang@amd.com>
Link: https://lore.kernel.org/r/20250225213937.2471419-3-huibo.wang@amd.com
[sean: tweak comments, fix formatting goofs]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Convert VMGEXIT SW_EXITINFO1 codes from plain numbers to proper defines.
Opportunistically update the comment for the malformed input "sub-error"
codes to state that they are defined by the GHCB, and to capure the
relationship to the malformed input response.
No functional change intended.
Signed-off-by: Melody Wang <huibo.wang@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pavan Kumar Paluri <papaluri@amd.com>
Link: https://lore.kernel.org/r/20250225213937.2471419-2-huibo.wang@amd.com
[sean: update comments]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Open code the filling of vcpu->arch.exception in kvm_requeue_exception()
instead of bouncing through kvm_multiple_exception(), as re-injection
doesn't actually share that much code with "normal" injection, e.g. the
VM-Exit interception check, payload delivery, and nested exception code
is all bypassed as those flows only apply during initial injection.
When FRED comes along, the special casing will only get worse, as FRED
explicitly tracks nested exceptions and essentially delivers the payload
on the stack frame, i.e. re-injection will need more inputs, and normal
injection will have yet more code that needs to be bypassed when KVM is
re-injecting an exception.
No functional change intended.
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20241001050110.3643764-2-xin@zytor.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Defer runtime CPUID updates until the next non-faulting CPUID emulation
or KVM_GET_CPUID2, which are the only paths in KVM that consume the
dynamic entries. Deferring the updates is especially beneficial to
nested VM-Enter/VM-Exit, as KVM will almost always detect multiple state
changes, not to mention the updates don't need to be realized while L2 is
active if CPUID is being intercepted by L1 (CPUID is a mandatory intercept
on Intel, but not AMD).
Deferring CPUID updates shaves several hundred cycles from nested VMX
roundtrips, as measured from L2 executing CPUID in a tight loop:
SKX 6850 => 6450
ICX 9000 => 8800
EMR 7900 => 7700
Alternatively, KVM could update only the CPUID leaves that are affected
by the state change, e.g. update XSAVE info only if XCR0 or XSS changes,
but that adds non-trivial complexity and doesn't solve the underlying
problem of nested transitions potentially changing both XCR0 and XSS, on
both nested VM-Enter and VM-Exit.
Skipping updates entirely if L2 is active and CPUID is being intercepted
by L1 could work for the common case. However, simply skipping updates if
L2 is active is *very* subtly dangerous and complex. Most KVM updates are
triggered by changes to the current vCPU state, which may be L2 state,
whereas performing updates only for L1 would requiring detecting changes
to L1 state. KVM would need to either track relevant L1 state, or defer
runtime CPUID updates until the next nested VM-Exit. The former is ugly
and complex, while the latter comes with similar dangers to deferring all
CPUID updates, and would only address the nested VM-Enter path.
To guard against using stale data, disallow querying dynamic CPUID feature
bits, i.e. features that KVM updates at runtime, via a compile-time
assertion in guest_cpu_cap_has(). Exempt MWAIT from the rule, as the
MISC_ENABLE_NO_MWAIT means that MWAIT is _conditionally_ a dynamic CPUID
feature.
Note, the rule could be enforced for MWAIT as well, e.g. by querying guest
CPUID in kvm_emulate_monitor_mwait, but there's no obvious advtantage to
doing so, and allowing MWAIT for guest_cpuid_has() opens up a different can
of worms. MONITOR/MWAIT can't be virtualized (for a reasonable definition),
and the nature of the MWAIT_NEVER_UD_FAULTS and MISC_ENABLE_NO_MWAIT quirks
means checking X86_FEATURE_MWAIT outside of kvm_emulate_monitor_mwait() is
wrong for other reasons.
Beyond the aforementioned feature bits, the only other dynamic CPUID
(sub)leaves are the XSAVE sizes, and similar to MWAIT, consuming those
CPUID entries in KVM is all but guaranteed to be a bug. The layout for an
actual XSAVE buffer depends on the format (compacted or not) and
potentially the features that are actually enabled. E.g. see the logic in
fpstate_clear_xstate_component() needed to poke into the guest's effective
XSAVE state to clear MPX state on INIT. KVM does consume
CPUID.0xD.0.{EAX,EDX} in kvm_check_cpuid() and cpuid_get_supported_xcr0(),
but not EBX, which is the only dynamic output register in the leaf.
Link: https://lore.kernel.org/r/20241211013302.1347853-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Move the conditional loading of hardware DR6 with the guest's DR6 value
out of the core .vcpu_run() loop to fix a bug where KVM can load hardware
with a stale vcpu->arch.dr6.
When the guest accesses a DR and host userspace isn't debugging the guest,
KVM disables DR interception and loads the guest's values into hardware on
VM-Enter and saves them on VM-Exit. This allows the guest to access DRs
at will, e.g. so that a sequence of DR accesses to configure a breakpoint
only generates one VM-Exit.
For DR0-DR3, the logic/behavior is identical between VMX and SVM, and also
identical between KVM_DEBUGREG_BP_ENABLED (userspace debugging the guest)
and KVM_DEBUGREG_WONT_EXIT (guest using DRs), and so KVM handles loading
DR0-DR3 in common code, _outside_ of the core kvm_x86_ops.vcpu_run() loop.
But for DR6, the guest's value doesn't need to be loaded into hardware for
KVM_DEBUGREG_BP_ENABLED, and SVM provides a dedicated VMCB field whereas
VMX requires software to manually load the guest value, and so loading the
guest's value into DR6 is handled by {svm,vmx}_vcpu_run(), i.e. is done
_inside_ the core run loop.
Unfortunately, saving the guest values on VM-Exit is initiated by common
x86, again outside of the core run loop. If the guest modifies DR6 (in
hardware, when DR interception is disabled), and then the next VM-Exit is
a fastpath VM-Exit, KVM will reload hardware DR6 with vcpu->arch.dr6 and
clobber the guest's actual value.
The bug shows up primarily with nested VMX because KVM handles the VMX
preemption timer in the fastpath, and the window between hardware DR6
being modified (in guest context) and DR6 being read by guest software is
orders of magnitude larger in a nested setup. E.g. in non-nested, the
VMX preemption timer would need to fire precisely between #DB injection
and the #DB handler's read of DR6, whereas with a KVM-on-KVM setup, the
window where hardware DR6 is "dirty" extends all the way from L1 writing
DR6 to VMRESUME (in L1).
L1's view:
==========
<L1 disables DR interception>
CPU 0/KVM-7289 [023] d.... 2925.640961: kvm_entry: vcpu 0
A: L1 Writes DR6
CPU 0/KVM-7289 [023] d.... 2925.640963: <hack>: Set DRs, DR6 = 0xffff0ff1
B: CPU 0/KVM-7289 [023] d.... 2925.640967: kvm_exit: vcpu 0 reason EXTERNAL_INTERRUPT intr_info 0x800000ec
D: L1 reads DR6, arch.dr6 = 0
CPU 0/KVM-7289 [023] d.... 2925.640969: <hack>: Sync DRs, DR6 = 0xffff0ff0
CPU 0/KVM-7289 [023] d.... 2925.640976: kvm_entry: vcpu 0
L2 reads DR6, L1 disables DR interception
CPU 0/KVM-7289 [023] d.... 2925.640980: kvm_exit: vcpu 0 reason DR_ACCESS info1 0x0000000000000216
CPU 0/KVM-7289 [023] d.... 2925.640983: kvm_entry: vcpu 0
CPU 0/KVM-7289 [023] d.... 2925.640983: <hack>: Set DRs, DR6 = 0xffff0ff0
L2 detects failure
CPU 0/KVM-7289 [023] d.... 2925.640987: kvm_exit: vcpu 0 reason HLT
L1 reads DR6 (confirms failure)
CPU 0/KVM-7289 [023] d.... 2925.640990: <hack>: Sync DRs, DR6 = 0xffff0ff0
L0's view:
==========
L2 reads DR6, arch.dr6 = 0
CPU 23/KVM-5046 [001] d.... 3410.005610: kvm_exit: vcpu 23 reason DR_ACCESS info1 0x0000000000000216
CPU 23/KVM-5046 [001] ..... 3410.005610: kvm_nested_vmexit: vcpu 23 reason DR_ACCESS info1 0x0000000000000216
L2 => L1 nested VM-Exit
CPU 23/KVM-5046 [001] ..... 3410.005610: kvm_nested_vmexit_inject: reason: DR_ACCESS ext_inf1: 0x0000000000000216
CPU 23/KVM-5046 [001] d.... 3410.005610: kvm_entry: vcpu 23
CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_exit: vcpu 23 reason VMREAD
CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_entry: vcpu 23
CPU 23/KVM-5046 [001] d.... 3410.005612: kvm_exit: vcpu 23 reason VMREAD
CPU 23/KVM-5046 [001] d.... 3410.005612: kvm_entry: vcpu 23
L1 writes DR7, L0 disables DR interception
CPU 23/KVM-5046 [001] d.... 3410.005612: kvm_exit: vcpu 23 reason DR_ACCESS info1 0x0000000000000007
CPU 23/KVM-5046 [001] d.... 3410.005613: kvm_entry: vcpu 23
L0 writes DR6 = 0 (arch.dr6)
CPU 23/KVM-5046 [001] d.... 3410.005613: <hack>: Set DRs, DR6 = 0xffff0ff0
A: <L1 writes DR6 = 1, no interception, arch.dr6 is still '0'>
B: CPU 23/KVM-5046 [001] d.... 3410.005614: kvm_exit: vcpu 23 reason PREEMPTION_TIMER
CPU 23/KVM-5046 [001] d.... 3410.005614: kvm_entry: vcpu 23
C: L0 writes DR6 = 0 (arch.dr6)
CPU 23/KVM-5046 [001] d.... 3410.005614: <hack>: Set DRs, DR6 = 0xffff0ff0
L1 => L2 nested VM-Enter
CPU 23/KVM-5046 [001] d.... 3410.005616: kvm_exit: vcpu 23 reason VMRESUME
L0 reads DR6, arch.dr6 = 0
Reported-by: John Stultz <jstultz@google.com>
Closes: https://lkml.kernel.org/r/CANDhNCq5_F3HfFYABqFGCA1bPd_%2BxgNj-iDQhH4tDk%2Bwi8iZZg%40mail.gmail.com
Fixes: 375e28ffc0 ("KVM: X86: Set host DR6 only on VMX and for KVM_DEBUGREG_WONT_EXIT")
Fixes: d67668e9dd ("KVM: x86, SVM: isolate vcpu->arch.dr6 from vmcb->save.dr6")
Cc: stable@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>
Tested-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20250125011833.3644371-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
- Overhaul KVM's CPUID feature infrastructure to replace "governed" features
with per-vCPU tracking of the vCPU's capabailities for all features. Along
the way, refactor the code to make it easier to add/modify features, and
add a variety of self-documenting macro types to again simplify adding new
features and to help readers understand KVM's handling of existing features.
- Rework KVM's handling of VM-Exits during event vectoring to plug holes where
KVM unintentionally puts the vCPU into infinite loops in some scenarios,
e.g. if emulation is triggered by the exit, and to bring parity between VMX
and SVM.
- Add pending request and interrupt injection information to the kvm_exit and
kvm_entry tracepoints respectively.
- Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
loading guest/host PKRU due to a refactoring of the kernel helpers that
didn't account for KVM's pre-checking of the need to do WRPKRU.
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Merge tag 'kvm-x86-misc-6.14' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.14:
- Overhaul KVM's CPUID feature infrastructure to track all vCPU capabilities
instead of just those where KVM needs to manage state and/or explicitly
enable the feature in hardware. Along the way, refactor the code to make
it easier to add features, and to make it more self-documenting how KVM
is handling each feature.
- Rework KVM's handling of VM-Exits during event vectoring; this plugs holes
where KVM unintentionally puts the vCPU into infinite loops in some scenarios
(e.g. if emulation is triggered by the exit), and brings parity between VMX
and SVM.
- Add pending request and interrupt injection information to the kvm_exit and
kvm_entry tracepoints respectively.
- Fix a relatively benign flaw where KVM would end up redoing RDPKRU when
loading guest/host PKRU, due to a refactoring of the kernel helpers that
didn't account for KVM's pre-checking of the need to do WRPKRU.
- Macrofy the SEV=n version of the sev_xxx_guest() helpers so that the code is
optimized away when building with less than brilliant compilers.
- Remove a now-redundant TLB flush when guest CR4.PGE changes.
- Use str_enabled_disabled() to replace open coded strings.
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Merge tag 'kvm-x86-svm-6.14' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.14:
- Macrofy the SEV=n version of the sev_xxx_guest() helpers so that the code is
optimized away when building with less than brilliant compilers.
- Remove a now-redundant TLB flush when guest CR4.PGE changes.
- Use str_enabled_disabled() to replace open coded strings.
Drop KVM's arbitrary behavior of making DE_CFG.LFENCE_SERIALIZE read-only
for the guest, as rejecting writes can lead to guest crashes, e.g. Windows
in particular doesn't gracefully handle unexpected #GPs on the WRMSR, and
nothing in the AMD manuals suggests that LFENCE_SERIALIZE is read-only _if
it exists_.
KVM only allows LFENCE_SERIALIZE to be set, by the guest or host, if the
underlying CPU has X86_FEATURE_LFENCE_RDTSC, i.e. if LFENCE is guaranteed
to be serializing. So if the guest sets LFENCE_SERIALIZE, KVM will provide
the desired/correct behavior without any additional action (the guest's
value is never stuffed into hardware). And having LFENCE be serializing
even when it's not _required_ to be is a-ok from a functional perspective.
Fixes: 74a0e79df6 ("KVM: SVM: Disallow guest from changing userspace's MSR_AMD64_DE_CFG value")
Fixes: d1d93fa90f ("KVM: SVM: Add MSR-based feature support for serializing LFENCE")
Reported-by: Simon Pilkington <simonp.git@mailbox.org>
Closes: https://lore.kernel.org/all/52914da7-a97b-45ad-86a0-affdf8266c61@mailbox.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241211172952.1477605-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add VMX/SVM specific interrupt injection info the kvm_entry tracepoint.
As is done with kvm_exit, gather the information via a kvm_x86_ops hook
to avoid the moderately costly VMREADs on VMX when the tracepoint isn't
enabled.
Opportunistically rename the parameters in the get_exit_info()
declaration to match the names used by both SVM and VMX.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240910200350.264245-2-mlevitsk@redhat.com
[sean: drop is_guest_mode() change, use intr_info/error_code for names]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Detect unhandleable vectoring in check_emulate_instruction() to prevent
infinite retry loops on SVM, and to eliminate the main differences in how
VM-Exits during event vectoring are handled on SVM versus VMX. E.g. if
the vCPU puts its IDT in emulated MMIO memory and generates an event,
without the check_emulate_instruction() change, SVM will re-inject the
event and resume the guest, and effectively put the vCPU into an infinite
loop.
Signed-off-by: Ivan Orlov <iorlov@amazon.com>
Link: https://lore.kernel.org/r/20241217181458.68690-6-iorlov@amazon.com
[sean: grab "svm" locally, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop the manual boot_cpu_has() checks on XSAVE when adjusting the guest's
XSAVES capabilities now that guest cpu_caps incorporates KVM's support.
The guest's cpu_caps are initialized from kvm_cpu_caps, which are in turn
initialized from boot_cpu_data, i.e. checking guest_cpu_cap_has() also
checks host/KVM capabilities (which is the entire point of cpu_caps).
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-52-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Switch all queries (except XSAVES) of guest features from guest CPUID to
guest capabilities, i.e. replace all calls to guest_cpuid_has() with calls
to guest_cpu_cap_has().
Keep guest_cpuid_has() around for XSAVES, but subsume its helper
guest_cpuid_get_register() and add a compile-time assertion to prevent
using guest_cpuid_has() for any other feature. Add yet another comment
for XSAVE to explain why KVM is allowed to query its raw guest CPUID.
Opportunistically drop the unused guest_cpuid_clear(), as there should be
no circumstance in which KVM needs to _clear_ a guest CPUID feature now
that everything is tracked via cpu_caps. E.g. KVM may need to _change_
a feature to emulate dynamic CPUID flags, but KVM should never need to
clear a feature in guest CPUID to prevent it from being used by the guest.
Delete the last remnants of the governed features framework, as the lone
holdout was vmx_adjust_secondary_exec_control()'s divergent behavior for
governed vs. ungoverned features.
Note, replacing guest_cpuid_has() checks with guest_cpu_cap_has() when
computing reserved CR4 bits is a nop when viewed as a whole, as KVM's
capabilities are already incorporated into the calculation, i.e. if a
feature is present in guest CPUID but unsupported by KVM, its CR4 bit
was already being marked as reserved, checking guest_cpu_cap_has() simply
double-stamps that it's a reserved bit.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-51-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Constrain all guest cpu_caps based on KVM support instead of constraining
only the few features that KVM _currently_ needs to verify are actually
supported by KVM. The intent of cpu_caps is to track what the guest is
actually capable of using, not the raw, unfiltered CPUID values that the
guest sees.
I.e. KVM should always consult it's only support when making decisions
based on guest CPUID, and the only reason KVM has historically made the
checks opt-in was due to lack of centralized tracking.
Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-45-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Initialize a vCPU's capabilities based on the guest CPUID provided by
userspace instead of simply zeroing the entire array. This is the first
step toward using cpu_caps to query *all* CPUID-based guest capabilities,
i.e. will allow converting all usage of guest_cpuid_has() to
guest_cpu_cap_has().
Zeroing the array was the logical choice when using cpu_caps was opt-in,
e.g. "unsupported" was generally a safer default, and the whole point of
governed features is that KVM would need to check host and guest support,
i.e. making everything unsupported by default didn't require more code.
But requiring KVM to manually "enable" every CPUID-based feature in
cpu_caps would require an absurd amount of boilerplate code.
Follow existing CPUID/kvm_cpu_caps nomenclature where possible, e.g. for
the change() and clear() APIs. Replace check_and_set() with constrain()
to try and capture that KVM is constraining userspace's desired guest
feature set based on KVM's capabilities.
This is intended to be gigantic nop, i.e. should not have any impact on
guest or KVM functionality.
This is also an intermediate step; a future commit will also incorporate
KVM support into the vCPU's cpu_caps before converting guest_cpuid_has()
to guest_cpu_cap_has().
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-42-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
As the first step toward replacing KVM's so-called "governed features"
framework with a more comprehensive, less poorly named implementation,
replace the "kvm_governed_feature" function prefix with "guest_cpu_cap"
and rename guest_can_use() to guest_cpu_cap_has().
The "guest_cpu_cap" naming scheme mirrors that of "kvm_cpu_cap", and
provides a more clear distinction between guest capabilities, which are
KVM controlled (heh, or one might say "governed"), and guest CPUID, which
with few exceptions is fully userspace controlled.
Opportunistically rewrite the comment about XSS passthrough for SEV-ES
guests to avoid referencing so many functions, as such comments are prone
to becoming stale (case in point...).
No functional change intended.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-40-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Drop SVM's direct TLB flush when CR4.PGE is toggled and NPT is enabled, as
KVM already guarantees TLBs are flushed appropriately.
For the call from cr_trap(), kvm_post_set_cr4() requests TLB_FLUSH_GUEST
(which is a superset of TLB_FLUSH_CURRENT) when CR4.PGE is toggled,
regardless of whether or not KVM is using TDP.
The calls from nested_vmcb02_prepare_save() and nested_svm_vmexit() are
checking guest (L2) vs. host (L1) CR4, and so a flush is unnecessary as L2
is defined to use a different ASID (from L1's perspective).
Lastly, the call from svm_set_cr0() passes in the current CR4 value, i.e.
can't toggle PGE.
Link: https://lore.kernel.org/r/20241127235312.4048445-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
- Clean up and optimize KVM's handling of writes to MSR_IA32_APICBASE.
- Quirk KVM's misguided behavior of initialized certain feature MSRs to
their maximum supported feature set, which can result in KVM creating
invalid vCPU state. E.g. initializing PERF_CAPABILITIES to a non-zero
value results in the vCPU having invalid state if userspace hides PDCM
from the guest, which can lead to save/restore failures.
- Fix KVM's handling of non-canonical checks for vCPUs that support LA57
to better follow the "architecture", in quotes because the actual
behavior is poorly documented. E.g. most MSR writes and descriptor
table loads ignore CR4.LA57 and operate purely on whether the CPU
supports LA57.
- Bypass the register cache when querying CPL from kvm_sched_out(), as
filling the cache from IRQ context is generally unsafe, and harden the
cache accessors to try to prevent similar issues from occuring in the
future.
- Advertise AMD_IBPB_RET to userspace, and fix a related bug where KVM
over-advertises SPEC_CTRL when trying to support cross-vendor VMs.
- Minor cleanups
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Merge tag 'kvm-x86-misc-6.13' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.13
- Clean up and optimize KVM's handling of writes to MSR_IA32_APICBASE.
- Quirk KVM's misguided behavior of initialized certain feature MSRs to
their maximum supported feature set, which can result in KVM creating
invalid vCPU state. E.g. initializing PERF_CAPABILITIES to a non-zero
value results in the vCPU having invalid state if userspace hides PDCM
from the guest, which can lead to save/restore failures.
- Fix KVM's handling of non-canonical checks for vCPUs that support LA57
to better follow the "architecture", in quotes because the actual
behavior is poorly documented. E.g. most MSR writes and descriptor
table loads ignore CR4.LA57 and operate purely on whether the CPU
supports LA57.
- Bypass the register cache when querying CPL from kvm_sched_out(), as
filling the cache from IRQ context is generally unsafe, and harden the
cache accessors to try to prevent similar issues from occuring in the
future.
- Advertise AMD_IBPB_RET to userspace, and fix a related bug where KVM
over-advertises SPEC_CTRL when trying to support cross-vendor VMs.
- Minor cleanups
Add a quirk to control KVM's misguided initialization of select feature
MSRs to KVM's max configuration, as enabling features by default violates
KVM's approach of letting userspace own the vCPU model, and is actively
problematic for MSRs that are conditionally supported, as the vCPU will
end up with an MSR value that userspace can't restore. E.g. if the vCPU
is configured with PDCM=0, userspace will save and attempt to restore a
non-zero PERF_CAPABILITIES, thanks to KVM's meddling.
Link: https://lore.kernel.org/r/20240802185511.305849-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
When querying guest CPL to determine if a vCPU was preempted while in
kernel mode, bypass the register cache, i.e. always read SS.AR_BYTES from
the VMCS on Intel CPUs. If the kernel is running with full preemption
enabled, using the register cache in the preemption path can result in
stale and/or uninitialized data being cached in the segment cache.
In particular the following scenario is currently possible:
- vCPU is just created, and the vCPU thread is preempted before
SS.AR_BYTES is written in vmx_vcpu_reset().
- When scheduling out the vCPU task, kvm_arch_vcpu_in_kernel() =>
vmx_get_cpl() reads and caches '0' for SS.AR_BYTES.
- vmx_vcpu_reset() => seg_setup() configures SS.AR_BYTES, but doesn't
invoke vmx_segment_cache_clear() to invalidate the cache.
As a result, KVM retains a stale value in the cache, which can be read,
e.g. via KVM_GET_SREGS. Usually this is not a problem because the VMX
segment cache is reset on each VM-Exit, but if the userspace VMM (e.g KVM
selftests) reads and writes system registers just after the vCPU was
created, _without_ modifying SS.AR_BYTES, userspace will write back the
stale '0' value and ultimately will trigger a VM-Entry failure due to
incorrect SS segment type.
Note, the VM-Enter failure can also be avoided by moving the call to
vmx_segment_cache_clear() until after the vmx_vcpu_reset() initializes all
segments. However, while that change is correct and desirable (and will
come along shortly), it does not address the underlying problem that
accessing KVM's register caches from !task context is generally unsafe.
In addition to fixing the immediate bug, bypassing the cache for this
particular case will allow hardening KVM register caching log to assert
that the caches are accessed only when KVM _knows_ it is safe to do so.
Fixes: de63ad4cf4 ("KVM: X86: implement the logic for spinlock optimization")
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Closes: https://lore.kernel.org/all/20240716022014.240960-3-mlevitsk@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241009175002.1118178-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Now that all kvm_vcpu_{,un}map() users pass "true" for @dirty, have them
pass "true" as a @writable param to kvm_vcpu_map(), and thus create a
read-only mapping when possible.
Note, creating read-only mappings can be theoretically slower, as they
don't play nice with fast GUP due to the need to break CoW before mapping
the underlying PFN. But practically speaking, creating a mapping isn't
a super hot path, and getting a writable mapping for reading is weird and
confusing.
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-34-seanjc@google.com>
KVM SVM changes for 6.12:
- Don't stuff the RSB after VM-Exit when RETPOLINE=y and AutoIBRS is enabled,
i.e. when the CPU has already flushed the RSB.
- Trace the per-CPU host save area as a VMCB pointer to improve readability
and cleanup the retrieval of the SEV-ES host save area.
- Remove unnecessary accounting of temporary nested VMCB related allocations.
KVM x86 misc changes for 6.12
- Advertise AVX10.1 to userspace (effectively prep work for the "real" AVX10
functionality that is on the horizon).
- Rework common MSR handling code to suppress errors on userspace accesses to
unsupported-but-advertised MSRs. This will allow removing (almost?) all of
KVM's exemptions for userspace access to MSRs that shouldn't exist based on
the vCPU model (the actual cleanup is non-trivial future work).
- Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC) splits the
64-bit value into the legacy ICR and ICR2 storage, whereas Intel (APICv)
stores the entire 64-bit value a the ICR offset.
- Fix a bug where KVM would fail to exit to userspace if one was triggered by
a fastpath exit handler.
- Add fastpath handling of HLT VM-Exit to expedite re-entering the guest when
there's already a pending wake event at the time of the exit.
- Finally fix the RSM vs. nested VM-Enter WARN by forcing the vCPU out of
guest mode prior to signalling SHUTDOWN (architecturally, the SHUTDOWN is
supposed to hit L1, not L2).
Register KVM's cpuhp and syscore callbacks when enabling virtualization in
hardware, as the sole purpose of said callbacks is to disable and re-enable
virtualization as needed.
The primary motivation for this series is to simplify dealing with enabling
virtualization for Intel's TDX, which needs to enable virtualization
when kvm-intel.ko is loaded, i.e. long before the first VM is created.
That said, this is a nice cleanup on its own. By registering the callbacks
on-demand, the callbacks themselves don't need to check kvm_usage_count,
because their very existence implies a non-zero count.
Patch 1 (re)adds a dedicated lock for kvm_usage_count. This avoids a
lock ordering issue between cpus_read_lock() and kvm_lock. The lock
ordering issue still exist in very rare cases, and will be fixed for
good by switching vm_list to an (S)RCU-protected list.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Register the "disable virtualization in an emergency" callback just
before KVM enables virtualization in hardware, as there is no functional
need to keep the callbacks registered while KVM happens to be loaded, but
is inactive, i.e. if KVM hasn't enabled virtualization.
Note, unregistering the callback every time the last VM is destroyed could
have measurable latency due to the synchronize_rcu() needed to ensure all
references to the callback are dropped before KVM is unloaded. But the
latency should be a small fraction of the total latency of disabling
virtualization across all CPUs, and userspace can set enable_virt_at_load
to completely eliminate the runtime overhead.
Add a pointer in kvm_x86_ops to allow vendor code to provide its callback.
There is no reason to force vendor code to do the registration, and either
way KVM would need a new kvm_x86_ops hook.
Suggested-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240830043600.127750-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename x86's the per-CPU vendor hooks used to enable virtualization in
hardware to align with the recently renamed arch hooks.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Message-ID: <20240830043600.127750-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a fastpath for HLT VM-Exits by immediately re-entering the guest if
it has a pending wake event. When virtual interrupt delivery is enabled,
i.e. when KVM doesn't need to manually inject interrupts, this allows KVM
to stay in the fastpath run loop when a vIRQ arrives between the guest
doing CLI and STI;HLT. Without AMD's Idle HLT-intercept support, the CPU
generates a HLT VM-Exit even though KVM will immediately resume the guest.
Note, on bare metal, it's relatively uncommon for a modern guest kernel to
actually trigger this scenario, as the window between the guest checking
for a wake event and committing to HLT is quite small. But in a nested
environment, the timings change significantly, e.g. rudimentary testing
showed that ~50% of HLT exits where HLT-polling was successful would be
serviced by this fastpath, i.e. ~50% of the time that a nested vCPU gets
a wake event before KVM schedules out the vCPU, the wake event was pending
even before the VM-Exit.
Link: https://lore.kernel.org/all/20240528041926.3989-3-manali.shukla@amd.com
Link: https://lore.kernel.org/r/20240802195120.325560-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The host save area is a VMCB, track it as such to help readers follow
along, but mostly to cleanup/simplify the retrieval of the SEV-ES host
save area.
Note, the compile-time assertion that
offsetof(struct vmcb, save) == EXPECTED_VMCB_CONTROL_AREA_SIZE
ensures that the SEV-ES save area is indeed at offset 0x400 (whoever added
the expected/architectural VMCB offsets apparently likes decimal).
No functional change intended.
Link: https://lore.kernel.org/r/20240802204511.352017-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add __sme_pa_to_page() to pair with __sme_page_pa() and use it to replace
open coded equivalents, including for "iopm_base", which previously
avoided having to do __sme_clr() by storing the raw PA in the global
variable.
Opportunistically convert __sme_page_pa() to a helper to provide type
safety.
No functional change intended.
Link: https://lore.kernel.org/r/20240802204511.352017-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Re-introduce the "split" x2APIC ICR storage that KVM used prior to Intel's
IPI virtualization support, but only for AMD. While not stated anywhere
in the APM, despite stating the ICR is a single 64-bit register, AMD CPUs
store the 64-bit ICR as two separate 32-bit values in ICR and ICR2. When
IPI virtualization (IPIv on Intel, all AVIC flavors on AMD) is enabled,
KVM needs to match CPU behavior as some ICR ICR writes will be handled by
the CPU, not by KVM.
Add a kvm_x86_ops knob to control the underlying format used by the CPU to
store the x2APIC ICR, and tune it to AMD vs. Intel regardless of whether
or not x2AVIC is enabled. If KVM is handling all ICR writes, the storage
format for x2APIC mode doesn't matter, and having the behavior follow AMD
versus Intel will provide better test coverage and ease debugging.
Fixes: 4d1d7942e3 ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode")
Cc: stable@vger.kernel.org
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20240719235107.3023592-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
If host supports Bus Lock Detect, KVM advertises it to guests even if
SVM support is absent. Additionally, guest wouldn't be able to use it
despite guest CPUID bit being set. Fix it by unconditionally clearing
the feature bit in KVM cpu capability.
Reported-by: Jim Mattson <jmattson@google.com>
Closes: https://lore.kernel.org/r/CALMp9eRet6+v8Y1Q-i6mqPm4hUow_kJNhmVHfOV8tMfuSS=tVg@mail.gmail.com
Fixes: 76ea438b4a ("KVM: X86: Expose bus lock debug exception to guest")
Cc: stable@vger.kernel.org
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240808062937.1149-4-ravi.bangoria@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Rename all APIs related to feature MSRs from get_msr_feature() to
get_feature_msr(). The APIs get "feature MSRs", not "MSR features".
And unlike kvm_{g,s}et_msr_common(), the "feature" adjective doesn't
describe the helper itself.
No functional change intended.
Link: https://lore.kernel.org/r/20240802181935.292540-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Refactor get_msr_feature() to take the index and data pointer as distinct
parameters in anticipation of eliminating "struct kvm_msr_entry" usage
further up the primary callchain.
No functional change intended.
Link: https://lore.kernel.org/r/20240802181935.292540-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Rename the "INVALID" internal MSR error return code to "UNSUPPORTED" to
try and make it more clear that access was denied because the MSR itself
is unsupported/unknown. "INVALID" is too ambiguous, as it could just as
easily mean the value for WRMSR as invalid.
Avoid UNKNOWN and UNIMPLEMENTED, as the error code is used for MSRs that
_are_ actually implemented by KVM, e.g. if the MSR is unsupported because
an associated feature flag is not present in guest CPUID.
Opportunistically beef up the comments for the internal MSR error codes.
Link: https://lore.kernel.org/r/20240802181935.292540-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Inject a #GP if the guest attempts to change MSR_AMD64_DE_CFG from its
*current* value, not if the guest attempts to write a value other than
KVM's set of supported bits. As per the comment and the changelog of the
original code, the intent is to effectively make MSR_AMD64_DE_CFG read-
only for the guest.
Opportunistically use a more conventional equality check instead of an
exclusive-OR check to detect attempts to change bits.
Fixes: d1d93fa90f ("KVM: SVM: Add MSR-based feature support for serializing LFENCE")
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240802181935.292540-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
If these msrs are read by the emulator (e.g due to 'force emulation' prefix),
SVM code currently fails to extract the corresponding segment bases,
and return them to the emulator.
Fix that.
Cc: stable@vger.kernel.org
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240802151608.72896-3-mlevitsk@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
KVM_PRE_FAULT_MEMORY for an SNP guest can race with
sev_gmem_post_populate() in bad ways. The following sequence for
instance can potentially trigger an RMP fault:
thread A, sev_gmem_post_populate: called
thread B, sev_gmem_prepare: places below 'pfn' in a private state in RMP
thread A, sev_gmem_post_populate: *vaddr = kmap_local_pfn(pfn + i);
thread A, sev_gmem_post_populate: copy_from_user(vaddr, src + i * PAGE_SIZE, PAGE_SIZE);
RMP #PF
Fix this by only allowing KVM_PRE_FAULT_MEMORY to run after a guest's
initial private memory contents have been finalized via
KVM_SEV_SNP_LAUNCH_FINISH.
Beyond fixing this issue, it just sort of makes sense to enforce this,
since the KVM_PRE_FAULT_MEMORY documentation states:
"KVM maps memory as if the vCPU generated a stage-2 read page fault"
which sort of implies we should be acting on the same guest state that a
vCPU would see post-launch after the initial guest memory is all set up.
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Make per-CPU save_area allocations NUMA-aware.
- Force sev_es_host_save_area() to be inlined to avoid calling into an
instrumentable function from noinstr code.
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Merge tag 'kvm-x86-svm-6.11' of https://github.com/kvm-x86/linux into HEAD
KVM SVM changes for 6.11
- Make per-CPU save_area allocations NUMA-aware.
- Force sev_es_host_save_area() to be inlined to avoid calling into an
instrumentable function from noinstr code.
- Add a global struct to consolidate tracking of host values, e.g. EFER, and
move "shadow_phys_bits" into the structure as "maxphyaddr".
- Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
bus frequency, because TDX.
- Print the name of the APICv/AVIC inhibits in the relevant tracepoint.
- Clean up KVM's handling of vendor specific emulation to consistently act on
"compatible with Intel/AMD", versus checking for a specific vendor.
- Misc cleanups
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Merge tag 'kvm-x86-misc-6.11' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.11
- Add a global struct to consolidate tracking of host values, e.g. EFER, and
move "shadow_phys_bits" into the structure as "maxphyaddr".
- Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
bus frequency, because TDX.
- Print the name of the APICv/AVIC inhibits in the relevant tracepoint.
- Clean up KVM's handling of vendor specific emulation to consistently act on
"compatible with Intel/AMD", versus checking for a specific vendor.
- Misc cleanups
- Enable halt poll shrinking by default, as Intel found it to be a clear win.
- Setup empty IRQ routing when creating a VM to avoid having to synchronize
SRCU when creating a split IRQCHIP on x86.
- Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
that arch code can use for hooking both sched_in() and sched_out().
- Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
truncating a bogus value from userspace, e.g. to help userspace detect bugs.
- Mark a vCPU as preempted if and only if it's scheduled out while in the
KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
memory when retrieving guest state during live migration blackout.
- A few minor cleanups
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Merge tag 'kvm-x86-generic-6.11' of https://github.com/kvm-x86/linux into HEAD
KVM generic changes for 6.11
- Enable halt poll shrinking by default, as Intel found it to be a clear win.
- Setup empty IRQ routing when creating a VM to avoid having to synchronize
SRCU when creating a split IRQCHIP on x86.
- Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
that arch code can use for hooking both sched_in() and sched_out().
- Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
truncating a bogus value from userspace, e.g. to help userspace detect bugs.
- Mark a vCPU as preempted if and only if it's scheduled out while in the
KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
memory when retrieving guest state during live migration blackout.
- A few minor cleanups
1. Add ParaVirt steal time support.
2. Add some VM migration enhancement.
3. Add perf kvm-stat support for loongarch.
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Merge tag 'loongarch-kvm-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD
LoongArch KVM changes for v6.11
1. Add ParaVirt steal time support.
2. Add some VM migration enhancement.
3. Add perf kvm-stat support for loongarch.
Use sev_es_host_save_area() instead of open coding an equivalent when
setting the MSR_TSC_AUX field during setup.
No functional change intended.
Link: https://lore.kernel.org/r/20240617210432.1642542-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Force sev_es_host_save_area() to be always inlined, as it's used in the
low level VM-Enter/VM-Exit path, which is non-instrumentable.
vmlinux.o: warning: objtool: svm_vcpu_enter_exit+0xb0: call to
sev_es_host_save_area() leaves .noinstr.text section
vmlinux.o: warning: objtool: svm_vcpu_enter_exit+0xbf: call to
sev_es_host_save_area.isra.0() leaves .noinstr.text section
Fixes: c92be2fd8e ("KVM: SVM: Save/restore non-volatile GPRs in SEV-ES VMRUN via host save area")
Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240617210432.1642542-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add module descriptions for the vendor modules to fix allmodconfig
'make W=1' warnings:
WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/kvm/kvm-intel.o
WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/kvm/kvm-amd.o
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240622-md-kvm-v2-1-29a60f7c48b1@quicinc.com
[sean: split kvm.ko change to separate commit]
Signed-off-by: Sean Christopherson <seanjc@google.com>
With commit 27bd5fdc24 ("KVM: SEV-ES: Prevent MSR access post VMSA
encryption"), older VMMs like QEMU 9.0 and older will fail when booting
SEV-ES guests with something like the following error:
qemu-system-x86_64: error: failed to get MSR 0x174
qemu-system-x86_64: ../qemu.git/target/i386/kvm/kvm.c:3950: kvm_get_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
This is because older VMMs that might still call
svm_get_msr()/svm_set_msr() for SEV-ES guests after guest boot even if
those interfaces were essentially just noops because of the vCPU state
being encrypted and stored separately in the VMSA. Now those VMMs will
get an -EINVAL and generally crash.
Newer VMMs that are aware of KVM_SEV_INIT2 however are already aware of
the stricter limitations of what vCPU state can be sync'd during
guest run-time, so newer QEMU for instance will work both for legacy
KVM_SEV_ES_INIT interface as well as KVM_SEV_INIT2.
So when using KVM_SEV_INIT2 it's okay to assume userspace can deal with
-EINVAL, whereas for legacy KVM_SEV_ES_INIT the kernel might be dealing
with either an older VMM and so it needs to assume that returning
-EINVAL might break the VMM.
Address this by only returning -EINVAL if the guest was started with
KVM_SEV_INIT2. Otherwise, just silently return.
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Nikunj A Dadhania <nikunj@amd.com>
Reported-by: Srikanth Aithal <sraithal@amd.com>
Closes: https://lore.kernel.org/lkml/37usuu4yu4ok7be2hqexhmcyopluuiqj3k266z4gajc2rcj4yo@eujb23qc3zcm/
Fixes: 27bd5fdc24 ("KVM: SEV-ES: Prevent MSR access post VMSA encryption")
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240604233510.764949-1-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fold the guts of kvm_arch_sched_in() into kvm_arch_vcpu_load(), keying
off the recently added kvm_vcpu.scheduled_out as appropriate.
Note, there is a very slight functional change, as PLE shrink updates will
now happen after blasting WBINVD, but that is quite uninteresting as the
two operations do not interact in any way.
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Emulate bits 63:32 of the SYSENTER_R{I,S}P MSRs for all vCPUs that are
compatible with Intel's architecture, not just strictly vCPUs that have
vendor==Intel. The behavior of bits 63:32 is architecturally defined in
the SDM, i.e. not some uarch specific quirk of Intel CPUs.
Link: https://lore.kernel.org/r/20240405235603.1173076-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
save_area of per-CPU svm_data are dominantly accessed from their
own local CPUs, so allocate them node-local for performance reason
so rename __snp_safe_alloc_page as snp_safe_alloc_page_node which
accepts numa node id as input parameter, svm_cpu_init call it with
node id switched from cpu id
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-4-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The allocation for the per-CPU save area in svm_cpu_init shouldn't
be accounted, So introduce __snp_safe_alloc_page helper, which has
gfp flag as input, svm_cpu_init calls __snp_safe_alloc_page with
GFP_KERNEL, snp_safe_alloc_page calls __snp_safe_alloc_page with
GFP_KERNEL_ACCOUNT as input
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-3-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
The input parameter 'vcpu' in snp_safe_alloc_page is not used.
Therefore, remove it.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240520120858.13117-2-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Pull base x86 KVM support for running SEV-SNP guests from Michael Roth:
* add some basic infrastructure and introduces a new KVM_X86_SNP_VM
vm_type to handle differences versus the existing KVM_X86_SEV_VM and
KVM_X86_SEV_ES_VM types.
* implement the KVM API to handle the creation of a cryptographic
launch context, encrypt/measure the initial image into guest memory,
and finalize it before launching it.
* implement handling for various guest-generated events such as page
state changes, onlining of additional vCPUs, etc.
* implement the gmem/mmu hooks needed to prepare gmem-allocated pages
before mapping them into guest private memory ranges as well as
cleaning them up prior to returning them to the host for use as
normal memory. Because those cleanup hooks supplant certain
activities like issuing WBINVDs during KVM MMU invalidations, avoid
duplicating that work to avoid unecessary overhead.
This merge leaves out support support for attestation guest requests
and for loading the signing keys to be used for attestation requests.
As documented in APM[1], LBR Virtualization must be enabled for SEV-ES
guests. Although KVM currently enforces LBRV for SEV-ES guests, there
are multiple issues with it:
o MSR_IA32_DEBUGCTLMSR is still intercepted. Since MSR_IA32_DEBUGCTLMSR
interception is used to dynamically toggle LBRV for performance reasons,
this can be fatal for SEV-ES guests. For ex SEV-ES guest on Zen3:
[guest ~]# wrmsr 0x1d9 0x4
KVM: entry failed, hardware error 0xffffffff
EAX=00000004 EBX=00000000 ECX=000001d9 EDX=00000000
Fix this by never intercepting MSR_IA32_DEBUGCTLMSR for SEV-ES guests.
No additional save/restore logic is required since MSR_IA32_DEBUGCTLMSR
is of swap type A.
o KVM will disable LBRV if userspace sets MSR_IA32_DEBUGCTLMSR before the
VMSA is encrypted. Fix this by moving LBRV enablement code post VMSA
encryption.
[1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
2023, Vol 2, 15.35.2 Enabling SEV-ES.
https://bugzilla.kernel.org/attachment.cgi?id=304653
Fixes: 376c6d2850 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading")
Co-developed-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Message-ID: <20240531044644.768-4-ravi.bangoria@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
As documented in APM[1], LBR Virtualization must be enabled for SEV-ES
guests. So, prevent SEV-ES guests when LBRV support is missing.
[1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
2023, Vol 2, 15.35.2 Enabling SEV-ES.
https://bugzilla.kernel.org/attachment.cgi?id=304653
Fixes: 376c6d2850 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading")
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Message-ID: <20240531044644.768-3-ravi.bangoria@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM currently allows userspace to read/write MSRs even after the VMSA is
encrypted. This can cause unintentional issues if MSR access has side-
effects. For ex, while migrating a guest, userspace could attempt to
migrate MSR_IA32_DEBUGCTLMSR and end up unintentionally disabling LBRV on
the target. Fix this by preventing access to those MSRs which are context
switched via the VMSA, once the VMSA is encrypted.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Message-ID: <20240531044644.768-2-ravi.bangoria@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
All SNP APs are initially started using the APIC INIT/SIPI sequence in
the guest. This sequence moves the AP MP state from
KVM_MP_STATE_UNINITIALIZED to KVM_MP_STATE_RUNNABLE, so there is no need
to attempt the UNBLOCK.
As it is, the UNBLOCK support in SVM is only enabled when AVIC is
enabled. When AVIC is disabled, AP creation is still successful.
Remove the KVM_REQ_UNBLOCK request from the AP creation code and revert
the changes to the vcpu_unblocking() kvm_x86_ops path.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When requesting an NMI window, WARN on vNMI support being enabled if and
only if NMIs are actually masked, i.e. if the vCPU is already handling an
NMI. KVM's ABI for NMIs that arrive simultanesouly (from KVM's point of
view) is to inject one NMI and pend the other. When using vNMI, KVM pends
the second NMI simply by setting V_NMI_PENDING, and lets the CPU do the
rest (hardware automatically sets V_NMI_BLOCKING when an NMI is injected).
However, if KVM can't immediately inject an NMI, e.g. because the vCPU is
in an STI shadow or is running with GIF=0, then KVM will request an NMI
window and trigger the WARN (but still function correctly).
Whether or not the GIF=0 case makes sense is debatable, as the intent of
KVM's behavior is to provide functionality that is as close to real
hardware as possible. E.g. if two NMIs are sent in quick succession, the
probability of both NMIs arriving in an STI shadow is infinitesimally low
on real hardware, but significantly larger in a virtual environment, e.g.
if the vCPU is preempted in the STI shadow. For GIF=0, the argument isn't
as clear cut, because the window where two NMIs can collide is much larger
in bare metal (though still small).
That said, KVM should not have divergent behavior for the GIF=0 case based
on whether or not vNMI support is enabled. And KVM has allowed
simultaneous NMIs with GIF=0 for over a decade, since commit 7460fb4a34
("KVM: Fix simultaneous NMIs"). I.e. KVM's GIF=0 handling shouldn't be
modified without a *really* good reason to do so, and if KVM's behavior
were to be modified, it should be done irrespective of vNMI support.
Fixes: fa4c027a79 ("KVM: x86: Add support for SVM's Virtual NMI")
Cc: stable@vger.kernel.org
Cc: Santosh Shukla <Santosh.Shukla@amd.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240522021435.1684366-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In the case of SEV-SNP, whether or not a 2MB page can be mapped via a
2MB mapping in the guest's nested page table depends on whether or not
any subpages within the range have already been initialized as private
in the RMP table. The existing mixed-attribute tracking in KVM is
insufficient here, for instance:
- gmem allocates 2MB page
- guest issues PVALIDATE on 2MB page
- guest later converts a subpage to shared
- SNP host code issues PSMASH to split 2MB RMP mapping to 4K
- KVM MMU splits NPT mapping to 4K
- guest later converts that shared page back to private
At this point there are no mixed attributes, and KVM would normally
allow for 2MB NPT mappings again, but this is actually not allowed
because the RMP table mappings are 4K and cannot be promoted on the
hypervisor side, so the NPT mappings must still be limited to 4K to
match this.
Implement a kvm_x86_ops.private_max_mapping_level() hook for SEV that
checks for this condition and adjusts the mapping level accordingly.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240501085210.2213060-16-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Implement a platform hook to do the work of restoring the direct map
entries of gmem-managed pages and transitioning the corresponding RMP
table entries back to the default shared/hypervisor-owned state.
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240501085210.2213060-15-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This will handle the RMP table updates needed to put a page into a
private state before mapping it into an SEV-SNP guest.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240501085210.2213060-14-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add support for the SEV-SNP AP Creation NAE event. This allows SEV-SNP
guests to alter the register state of the APs on their own. This allows
the guest a way of simulating INIT-SIPI.
A new event, KVM_REQ_UPDATE_PROTECTED_GUEST_STATE, is created and used
so as to avoid updating the VMSA pointer while the vCPU is running.
For CREATE
The guest supplies the GPA of the VMSA to be used for the vCPU with
the specified APIC ID. The GPA is saved in the svm struct of the
target vCPU, the KVM_REQ_UPDATE_PROTECTED_GUEST_STATE event is added
to the vCPU and then the vCPU is kicked.
For CREATE_ON_INIT:
The guest supplies the GPA of the VMSA to be used for the vCPU with
the specified APIC ID the next time an INIT is performed. The GPA is
saved in the svm struct of the target vCPU.
For DESTROY:
The guest indicates it wishes to stop the vCPU. The GPA is cleared
from the svm struct, the KVM_REQ_UPDATE_PROTECTED_GUEST_STATE event is
added to vCPU and then the vCPU is kicked.
The KVM_REQ_UPDATE_PROTECTED_GUEST_STATE event handler will be invoked
as a result of the event or as a result of an INIT. If a new VMSA is to
be installed, the VMSA guest page is set as the VMSA in the vCPU VMCB
and the vCPU state is set to KVM_MP_STATE_RUNNABLE. If a new VMSA is not
to be installed, the VMSA is cleared in the vCPU VMCB and the vCPU state
is set to KVM_MP_STATE_HALTED to prevent it from being run.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Message-ID: <20240501085210.2213060-13-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When SEV-SNP is enabled in the guest, the hardware places restrictions
on all memory accesses based on the contents of the RMP table. When
hardware encounters RMP check failure caused by the guest memory access
it raises the #NPF. The error code contains additional information on
the access type. See the APM volume 2 for additional information.
When using gmem, RMP faults resulting from mismatches between the state
in the RMP table vs. what the guest expects via its page table result
in KVM_EXIT_MEMORY_FAULTs being forwarded to userspace to handle. This
means the only expected case that needs to be handled in the kernel is
when the page size of the entry in the RMP table is larger than the
mapping in the nested page table, in which case a PSMASH instruction
needs to be issued to split the large RMP entry into individual 4K
entries so that subsequent accesses can succeed.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Message-ID: <20240501085210.2213060-12-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
SEV-SNP builds upon existing SEV and SEV-ES functionality while adding
new hardware-based security protection. SEV-SNP adds strong memory
encryption and integrity protection to help prevent malicious
hypervisor-based attacks such as data replay, memory re-mapping, and
more, to create an isolated execution environment.
Define a new KVM_X86_SNP_VM type which makes use of these capabilities
and extend the KVM_SEV_INIT2 ioctl to support it. Also add a basic
helper to check whether SNP is enabled and set PFERR_PRIVATE_ACCESS for
private #NPFs so they are handled appropriately by KVM MMU.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240501085210.2213060-5-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the sanity check that hardware never sets bits that collide with KVM-
define synthetic bits from kvm_mmu_page_fault() to npf_interception(),
i.e. make the sanity check #NPF specific. The legacy #PF path already
WARNs if _any_ of bits 63:32 are set, and the error code that comes from
VMX's EPT Violatation and Misconfig is 100% synthesized (KVM morphs VMX's
EXIT_QUALIFICATION into error code flags).
Add a compile-time assert in the legacy #PF handler to make sure that KVM-
define flags are covered by its existing sanity check on the upper bits.
Opportunistically add a description of PFERR_IMPLICIT_ACCESS, since we
are removing the comment that defined it.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Message-ID: <20240228024147.41573-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
SEV-ES allows passing custom contents for x87, SSE and AVX state into the VMSA.
Allow userspace to do that with the usual KVM_SET_XSAVE API and only mark
FPU contents as confidential after it has been copied and encrypted into
the VMSA.
Since the XSAVE state for AVX is the first, it does not need the
compacted-state handling of get_xsave_addr(). However, there are other
parts of XSAVE state in the VMSA that currently are not handled, and
the validation logic of get_xsave_addr() is pointless to duplicate
in KVM, so move get_xsave_addr() to public FPU API; it is really just
a facility to operate on XSAVE state and does not expose any internal
details of arch/x86/kernel/fpu.
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240404121327.3107131-12-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240404121327.3107131-11-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Right now, the set of features that are stored in the VMSA upon
initialization is fixed and depends on the module parameters for
kvm-amd.ko. However, the hypervisor cannot really change it at will
because the feature word has to match between the hypervisor and whatever
computes a measurement of the VMSA for attestation purposes.
Add a field to kvm_sev_info that holds the set of features to be stored
in the VMSA; and query it instead of referring to the module parameters.
Because KVM_SEV_INIT and KVM_SEV_ES_INIT accept no parameters, this
does not yet introduce any functional change, but it paves the way for
an API that allows customization of the features per-VM.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20240209183743.22030-6-pbonzini@redhat.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240404121327.3107131-7-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Compute the set of features to be stored in the VMSA when KVM is
initialized; move it from there into kvm_sev_info when SEV is initialized,
and then into the initial VMSA.
The new variable can then be used to return the set of supported features
to userspace, via the KVM_GET_DEVICE_ATTR ioctl.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-ID: <20240404121327.3107131-6-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stop compiling sev.c when CONFIG_KVM_AMD_SEV=n, as the number of #ifdefs
in sev.c is getting ridiculous, and having #ifdefs inside of SEV helpers
is quite confusing.
To minimize #ifdefs in code flows, #ifdef away only the kvm_x86_ops hooks
and the #VMGEXIT handler. Stubs are also restricted to functions that
check sev_enabled and to the destruction functions sev_free_cpu() and
sev_vm_destroy(), where the style of their callers is to leave checks
to the callers. Most call sites instead rely on dead code elimination
to take care of functions that are guarded with sev_guest() or
sev_es_guest().
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240404121327.3107131-3-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the host save area to save/restore non-volatile (callee-saved)
registers in __svm_sev_es_vcpu_run() to take advantage of hardware loading
all registers from the save area on #VMEXIT. KVM still needs to save the
registers it wants restored, but the loads are handled automatically by
hardware.
Aside from less assembly code, letting hardware do the restoration means
stack frames are preserved for the entirety of __svm_sev_es_vcpu_run().
Opportunistically add a comment to call out why @svm needs to be saved
across VMRUN->#VMEXIT, as it's not easy to decipher that from the macro
hell.
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Alexey Kardashevskiy <aik@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240223204233.3337324-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
* Changes to FPU handling came in via the main s390 pull request
* Only deliver to the guest the SCLP events that userspace has
requested.
* More virtual vs physical address fixes (only a cleanup since
virtual and physical address spaces are currently the same).
* Fix selftests undefined behavior.
x86:
* Fix a restriction that the guest can't program a PMU event whose
encoding matches an architectural event that isn't included in the
guest CPUID. The enumeration of an architectural event only says
that if a CPU supports an architectural event, then the event can be
programmed *using the architectural encoding*. The enumeration does
NOT say anything about the encoding when the CPU doesn't report support
the event *in general*. It might support it, and it might support it
using the same encoding that made it into the architectural PMU spec.
* Fix a variety of bugs in KVM's emulation of RDPMC (more details on
individual commits) and add a selftest to verify KVM correctly emulates
RDMPC, counter availability, and a variety of other PMC-related
behaviors that depend on guest CPUID and therefore are easier to
validate with selftests than with custom guests (aka kvm-unit-tests).
* Zero out PMU state on AMD if the virtual PMU is disabled, it does not
cause any bug but it wastes time in various cases where KVM would check
if a PMC event needs to be synthesized.
* Optimize triggering of emulated events, with a nice ~10% performance
improvement in VM-Exit microbenchmarks when a vPMU is exposed to the
guest.
* Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
* Fix a bug where KVM would report stale/bogus exit qualification information
when exiting to userspace with an internal error exit code.
* Add a VMX flag in /proc/cpuinfo to report 5-level EPT support.
* Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
* Tear down TDP MMU page tables at 4KiB granularity (used to be 1GiB). KVM
doesn't support yielding in the middle of processing a zap, and 1GiB
granularity resulted in multi-millisecond lags that are quite impolite
for CONFIG_PREEMPT kernels.
* Allocate write-tracking metadata on-demand to avoid the memory overhead when
a kernel is built with i915 virtualization support but the workloads use
neither shadow paging nor i915 virtualization.
* Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives.
* Fix the debugregs ABI for 32-bit KVM.
* Rework the "force immediate exit" code so that vendor code ultimately decides
how and when to force the exit, which allowed some optimization for both
Intel and AMD.
* Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, causing extra unnecessary work.
* Cleanup the logic for checking if the currently loaded vCPU is in-kernel.
* Harden against underflowing the active mmu_notifier invalidation
count, so that "bad" invalidations (usually due to bugs elsehwere in the
kernel) are detected earlier and are less likely to hang the kernel.
x86 Xen emulation:
* Overlay pages can now be cached based on host virtual address,
instead of guest physical addresses. This removes the need to
reconfigure and invalidate the cache if the guest changes the
gpa but the underlying host virtual address remains the same.
* When possible, use a single host TSC value when computing the deadline for
Xen timers in order to improve the accuracy of the timer emulation.
* Inject pending upcall events when the vCPU software-enables its APIC to fix
a bug where an upcall can be lost (and to follow Xen's behavior).
* Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
events fails, e.g. if the guest has aliased xAPIC IDs.
RISC-V:
* Support exception and interrupt handling in selftests
* New self test for RISC-V architectural timer (Sstc extension)
* New extension support (Ztso, Zacas)
* Support userspace emulation of random number seed CSRs.
ARM:
* Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
* Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
* Conversion of KVM's representation of LPIs to an xarray, utilized to
address serialization some of the serialization on the LPI injection
path
* Support for _architectural_ VHE-only systems, advertised through the
absence of FEAT_E2H0 in the CPU's ID register
* Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
LoongArch:
* Set reserved bits as zero in CPUCFG.
* Start SW timer only when vcpu is blocking.
* Do not restart SW timer when it is expired.
* Remove unnecessary CSR register saving during enter guest.
* Misc cleanups and fixes as usual.
Generic:
* cleanup Kconfig by removing CONFIG_HAVE_KVM, which was basically always
true on all architectures except MIPS (where Kconfig determines the
available depending on CPU capabilities). It is replaced either by
an architecture-dependent symbol for MIPS, and IS_ENABLED(CONFIG_KVM)
everywhere else.
* Factor common "select" statements in common code instead of requiring
each architecture to specify it
* Remove thoroughly obsolete APIs from the uapi headers.
* Move architecture-dependent stuff to uapi/asm/kvm.h
* Always flush the async page fault workqueue when a work item is being
removed, especially during vCPU destruction, to ensure that there are no
workers running in KVM code when all references to KVM-the-module are gone,
i.e. to prevent a very unlikely use-after-free if kvm.ko is unloaded.
* Grab a reference to the VM's mm_struct in the async #PF worker itself instead
of gifting the worker a reference, so that there's no need to remember
to *conditionally* clean up after the worker.
Selftests:
* Reduce boilerplate especially when utilize selftest TAP infrastructure.
* Add basic smoke tests for SEV and SEV-ES, along with a pile of library
support for handling private/encrypted/protected memory.
* Fix benign bugs where tests neglect to close() guest_memfd files.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm updates from Paolo Bonzini:
"S390:
- Changes to FPU handling came in via the main s390 pull request
- Only deliver to the guest the SCLP events that userspace has
requested
- More virtual vs physical address fixes (only a cleanup since
virtual and physical address spaces are currently the same)
- Fix selftests undefined behavior
x86:
- Fix a restriction that the guest can't program a PMU event whose
encoding matches an architectural event that isn't included in the
guest CPUID. The enumeration of an architectural event only says
that if a CPU supports an architectural event, then the event can
be programmed *using the architectural encoding*. The enumeration
does NOT say anything about the encoding when the CPU doesn't
report support the event *in general*. It might support it, and it
might support it using the same encoding that made it into the
architectural PMU spec
- Fix a variety of bugs in KVM's emulation of RDPMC (more details on
individual commits) and add a selftest to verify KVM correctly
emulates RDMPC, counter availability, and a variety of other
PMC-related behaviors that depend on guest CPUID and therefore are
easier to validate with selftests than with custom guests (aka
kvm-unit-tests)
- Zero out PMU state on AMD if the virtual PMU is disabled, it does
not cause any bug but it wastes time in various cases where KVM
would check if a PMC event needs to be synthesized
- Optimize triggering of emulated events, with a nice ~10%
performance improvement in VM-Exit microbenchmarks when a vPMU is
exposed to the guest
- Tighten the check for "PMI in guest" to reduce false positives if
an NMI arrives in the host while KVM is handling an IRQ VM-Exit
- Fix a bug where KVM would report stale/bogus exit qualification
information when exiting to userspace with an internal error exit
code
- Add a VMX flag in /proc/cpuinfo to report 5-level EPT support
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock
held for read, e.g. to avoid serializing vCPUs when userspace
deletes a memslot
- Tear down TDP MMU page tables at 4KiB granularity (used to be
1GiB). KVM doesn't support yielding in the middle of processing a
zap, and 1GiB granularity resulted in multi-millisecond lags that
are quite impolite for CONFIG_PREEMPT kernels
- Allocate write-tracking metadata on-demand to avoid the memory
overhead when a kernel is built with i915 virtualization support
but the workloads use neither shadow paging nor i915 virtualization
- Explicitly initialize a variety of on-stack variables in the
emulator that triggered KMSAN false positives
- Fix the debugregs ABI for 32-bit KVM
- Rework the "force immediate exit" code so that vendor code
ultimately decides how and when to force the exit, which allowed
some optimization for both Intel and AMD
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left
elevated if vCPU creation ultimately failed, causing extra
unnecessary work
- Cleanup the logic for checking if the currently loaded vCPU is
in-kernel
- Harden against underflowing the active mmu_notifier invalidation
count, so that "bad" invalidations (usually due to bugs elsehwere
in the kernel) are detected earlier and are less likely to hang the
kernel
x86 Xen emulation:
- Overlay pages can now be cached based on host virtual address,
instead of guest physical addresses. This removes the need to
reconfigure and invalidate the cache if the guest changes the gpa
but the underlying host virtual address remains the same
- When possible, use a single host TSC value when computing the
deadline for Xen timers in order to improve the accuracy of the
timer emulation
- Inject pending upcall events when the vCPU software-enables its
APIC to fix a bug where an upcall can be lost (and to follow Xen's
behavior)
- Fall back to the slow path instead of warning if "fast" IRQ
delivery of Xen events fails, e.g. if the guest has aliased xAPIC
IDs
RISC-V:
- Support exception and interrupt handling in selftests
- New self test for RISC-V architectural timer (Sstc extension)
- New extension support (Ztso, Zacas)
- Support userspace emulation of random number seed CSRs
ARM:
- Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
- Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
- Conversion of KVM's representation of LPIs to an xarray, utilized
to address serialization some of the serialization on the LPI
injection path
- Support for _architectural_ VHE-only systems, advertised through
the absence of FEAT_E2H0 in the CPU's ID register
- Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
LoongArch:
- Set reserved bits as zero in CPUCFG
- Start SW timer only when vcpu is blocking
- Do not restart SW timer when it is expired
- Remove unnecessary CSR register saving during enter guest
- Misc cleanups and fixes as usual
Generic:
- Clean up Kconfig by removing CONFIG_HAVE_KVM, which was basically
always true on all architectures except MIPS (where Kconfig
determines the available depending on CPU capabilities). It is
replaced either by an architecture-dependent symbol for MIPS, and
IS_ENABLED(CONFIG_KVM) everywhere else
- Factor common "select" statements in common code instead of
requiring each architecture to specify it
- Remove thoroughly obsolete APIs from the uapi headers
- Move architecture-dependent stuff to uapi/asm/kvm.h
- Always flush the async page fault workqueue when a work item is
being removed, especially during vCPU destruction, to ensure that
there are no workers running in KVM code when all references to
KVM-the-module are gone, i.e. to prevent a very unlikely
use-after-free if kvm.ko is unloaded
- Grab a reference to the VM's mm_struct in the async #PF worker
itself instead of gifting the worker a reference, so that there's
no need to remember to *conditionally* clean up after the worker
Selftests:
- Reduce boilerplate especially when utilize selftest TAP
infrastructure
- Add basic smoke tests for SEV and SEV-ES, along with a pile of
library support for handling private/encrypted/protected memory
- Fix benign bugs where tests neglect to close() guest_memfd files"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits)
selftests: kvm: remove meaningless assignments in Makefiles
KVM: riscv: selftests: Add Zacas extension to get-reg-list test
RISC-V: KVM: Allow Zacas extension for Guest/VM
KVM: riscv: selftests: Add Ztso extension to get-reg-list test
RISC-V: KVM: Allow Ztso extension for Guest/VM
RISC-V: KVM: Forward SEED CSR access to user space
KVM: riscv: selftests: Add sstc timer test
KVM: riscv: selftests: Change vcpu_has_ext to a common function
KVM: riscv: selftests: Add guest helper to get vcpu id
KVM: riscv: selftests: Add exception handling support
LoongArch: KVM: Remove unnecessary CSR register saving during enter guest
LoongArch: KVM: Do not restart SW timer when it is expired
LoongArch: KVM: Start SW timer only when vcpu is blocking
LoongArch: KVM: Set reserved bits as zero in CPUCFG
KVM: selftests: Explicitly close guest_memfd files in some gmem tests
KVM: x86/xen: fix recursive deadlock in timer injection
KVM: pfncache: simplify locking and make more self-contained
KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled
KVM: x86/xen: improve accuracy of Xen timers
...
- The biggest change is the rework of the percpu code,
to support the 'Named Address Spaces' GCC feature,
by Uros Bizjak:
- This allows C code to access GS and FS segment relative
memory via variables declared with such attributes,
which allows the compiler to better optimize those accesses
than the previous inline assembly code.
- The series also includes a number of micro-optimizations
for various percpu access methods, plus a number of
cleanups of %gs accesses in assembly code.
- These changes have been exposed to linux-next testing for
the last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally
working handling of FPU switching - which also generates
better code.
- Propagate more RIP-relative addressing in assembly code,
to generate slightly better code.
- Rework the CPU mitigations Kconfig space to be less idiosyncratic,
to make it easier for distros to follow & maintain these options.
- Rework the x86 idle code to cure RCU violations and
to clean up the logic.
- Clean up the vDSO Makefile logic.
- Misc cleanups and fixes.
[ Please note that there's a higher number of merge commits in
this branch (three) than is usual in x86 topic trees. This happened
due to the long testing lifecycle of the percpu changes that
involved 3 merge windows, which generated a longer history
and various interactions with other core x86 changes that we
felt better about to carry in a single branch. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core x86 updates from Ingo Molnar:
- The biggest change is the rework of the percpu code, to support the
'Named Address Spaces' GCC feature, by Uros Bizjak:
- This allows C code to access GS and FS segment relative memory
via variables declared with such attributes, which allows the
compiler to better optimize those accesses than the previous
inline assembly code.
- The series also includes a number of micro-optimizations for
various percpu access methods, plus a number of cleanups of %gs
accesses in assembly code.
- These changes have been exposed to linux-next testing for the
last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally working handling
of FPU switching - which also generates better code
- Propagate more RIP-relative addressing in assembly code, to generate
slightly better code
- Rework the CPU mitigations Kconfig space to be less idiosyncratic, to
make it easier for distros to follow & maintain these options
- Rework the x86 idle code to cure RCU violations and to clean up the
logic
- Clean up the vDSO Makefile logic
- Misc cleanups and fixes
* tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
x86/idle: Select idle routine only once
x86/idle: Let prefer_mwait_c1_over_halt() return bool
x86/idle: Cleanup idle_setup()
x86/idle: Clean up idle selection
x86/idle: Sanitize X86_BUG_AMD_E400 handling
sched/idle: Conditionally handle tick broadcast in default_idle_call()
x86: Increase brk randomness entropy for 64-bit systems
x86/vdso: Move vDSO to mmap region
x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
x86/retpoline: Ensure default return thunk isn't used at runtime
x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32
x86/vdso: Use $(addprefix ) instead of $(foreach )
x86/vdso: Simplify obj-y addition
x86/vdso: Consolidate targets and clean-files
x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK
x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO
x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY
x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY
x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS
...
Sean Christopherson