superrob1500
/
mirror-linux
mirror of https://github.com/torvalds/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

KVM: x86/mmu: Further check old SPTE is leaf for spurious prefetch fault 

Instead of simply treating a prefetch fault as spurious when there's a
shadow-present old SPTE, further check if the old SPTE is leaf to determine
if a prefetch fault is spurious.

It's not reasonable to treat a prefetch fault as spurious when there's a
shadow-present non-leaf SPTE without a corresponding shadow-present leaf
SPTE. e.g., in the following sequence, a prefetch fault should not be
considered spurious:
1. add a memslot with size 4K
2. prefault GPA A in the memslot
3. delete the memslot (zap all disabled)
4. re-add the memslot with size 2M
5. prefault GPA A again.
In step 5, the prefetch fault attempts to install a 2M huge entry.
Since step 3 zaps the leaf SPTE for GPA A while keeping the non-leaf SPTE,
the leaf entry will remain empty after step 5 if the fetch fault is
regarded as spurious due to a shadow-present non-leaf SPTE.

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Link: https://lore.kernel.org/r/20250318013111.5648-1-yan.y.zhao@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
pull/1255/head
Yan Zhao 2025-03-18 09:31:11 +08:00 committed by Sean Christopherson
parent 45eb29140e
commit ea9fcdf76d
2 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/kvm/mmu/mmu.c
View File

@ -3020,7 +3020,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,
}
if (is_shadow_present_pte(*sptep)) {
if (prefetch)
if (prefetch && is_last_spte(*sptep, level))
return RET_PF_SPURIOUS;
/*

3
arch/x86/kvm/mmu/tdp_mmu.c
View File

@ -1153,7 +1153,8 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
if (WARN_ON_ONCE(sp->role.level != fault->goal_level))
return RET_PF_RETRY;
if (fault->prefetch && is_shadow_present_pte(iter->old_spte))
if (fault->prefetch && is_shadow_present_pte(iter->old_spte) &&
is_last_spte(iter->old_spte, iter->level))
return RET_PF_SPURIOUS;
if (is_shadow_present_pte(iter->old_spte) &&