- x2apic_disable() clears x2apic_state and x2apic_mode unconditionally,
even when the state is X2APIC_ON_LOCKED, which prevents the kernel to
disable it thereby creating inconsistent state.
Reorder the logic so it actually works correctly
- The XSTATE logic for handling LBR is incorrect as it assumes that
XSAVES supports LBR when the CPU supports LBR. In fact both conditions
need to be true. Otherwise the enablement of LBR in the IA32_XSS MSR
fails and subsequently the machine crashes on the next XRSTORS
operation because IA32_XSS is not initialized.
Cache the XSTATE support bit during init and make the related functions
use this cached information and the LBR CPU feature bit to cure this.
- Cure a long standing bug in KASLR
KASLR uses the full address space between PAGE_OFFSET and vaddr_end to
randomize the starting points of the direct map, vmalloc and vmemmap
regions. It thereby limits the size of the direct map by using the
installed memory size plus an extra configurable margin for hot-plug
memory. This limitation is done to gain more randomization space
because otherwise only the holes between the direct map, vmalloc,
vmemmap and vaddr_end would be usable for randomizing.
The limited direct map size is not exposed to the rest of the kernel, so
the memory hot-plug and resource management related code paths still
operate under the assumption that the available address space can be
determined with MAX_PHYSMEM_BITS.
request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards. That means the first allocation happens past the end of the
direct map and if unlucky this address is in the vmalloc space, which
causes high_memory to become greater than VMALLOC_START and consequently
causes iounmap() to fail for valid ioremap addresses.
Cure this by exposing the end of the direct map via PHYSMEM_END and use
that for the memory hot-plug and resource management related places
instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END
maps to a variable which is initialized by the KASLR initialization and
otherwise it is based on MAX_PHYSMEM_BITS as before.
- Prevent a data leak in mmio_read(). The TDVMCALL exposes the value of
an initialized variabled on the stack to the VMM. The variable is only
required as output value, so it does not have to exposed to the VMM in
the first place.
- Prevent an array overrun in the resource control code on systems with
Sub-NUMA Clustering enabled because the code failed to adjust the index
by the number of SNC nodes per L3 cache.
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Merge tag 'x86-urgent-2024-09-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Thomas Gleixner:
- x2apic_disable() clears x2apic_state and x2apic_mode unconditionally,
even when the state is X2APIC_ON_LOCKED, which prevents the kernel to
disable it thereby creating inconsistent state.
Reorder the logic so it actually works correctly
- The XSTATE logic for handling LBR is incorrect as it assumes that
XSAVES supports LBR when the CPU supports LBR. In fact both
conditions need to be true. Otherwise the enablement of LBR in the
IA32_XSS MSR fails and subsequently the machine crashes on the next
XRSTORS operation because IA32_XSS is not initialized.
Cache the XSTATE support bit during init and make the related
functions use this cached information and the LBR CPU feature bit to
cure this.
- Cure a long standing bug in KASLR
KASLR uses the full address space between PAGE_OFFSET and vaddr_end
to randomize the starting points of the direct map, vmalloc and
vmemmap regions. It thereby limits the size of the direct map by
using the installed memory size plus an extra configurable margin for
hot-plug memory. This limitation is done to gain more randomization
space because otherwise only the holes between the direct map,
vmalloc, vmemmap and vaddr_end would be usable for randomizing.
The limited direct map size is not exposed to the rest of the kernel,
so the memory hot-plug and resource management related code paths
still operate under the assumption that the available address space
can be determined with MAX_PHYSMEM_BITS.
request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards. That means the first allocation happens past the end of
the direct map and if unlucky this address is in the vmalloc space,
which causes high_memory to become greater than VMALLOC_START and
consequently causes iounmap() to fail for valid ioremap addresses.
Cure this by exposing the end of the direct map via PHYSMEM_END and
use that for the memory hot-plug and resource management related
places instead of relying on MAX_PHYSMEM_BITS. In the KASLR case
PHYSMEM_END maps to a variable which is initialized by the KASLR
initialization and otherwise it is based on MAX_PHYSMEM_BITS as
before.
- Prevent a data leak in mmio_read(). The TDVMCALL exposes the value of
an initialized variabled on the stack to the VMM. The variable is
only required as output value, so it does not have to exposed to the
VMM in the first place.
- Prevent an array overrun in the resource control code on systems with
Sub-NUMA Clustering enabled because the code failed to adjust the
index by the number of SNC nodes per L3 cache.
* tag 'x86-urgent-2024-09-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/resctrl: Fix arch_mbm_* array overrun on SNC
x86/tdx: Fix data leak in mmio_read()
x86/kaslr: Expose and use the end of the physical memory address space
x86/fpu: Avoid writing LBR bit to IA32_XSS unless supported
x86/apic: Make x2apic_disable() work correctly
c9f016e72b