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KVM: x86/mmu: Don't treat fully writable SPTEs as volatile (modulo A/D)

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Don't treat SPTEs that are truly writable, i.e. writable in hardware, as
being volatile (unless they're volatile for other reasons, e.g. A/D bits).
KVM _sets_ the WRITABLE bit out of mmu_lock, but never _clears_ the bit
out of mmu_lock, so if the WRITABLE bit is set, it cannot magically get
cleared just because the SPTE is MMU-writable.

Rename the wrapper of MMU-writable to be more literal, the previous name
of spte_can_locklessly_be_made_writable() is wrong and misleading.

Fixes: c7ba5b48cc ("KVM: MMU: fast path of handling guest page fault")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220423034752.1161007-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-04-23 03:47:41 +00:00 committed by Paolo Bonzini
parent 44187235cb
commit 706c9c55e5
2 changed files with 10 additions and 9 deletions
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17
arch/x86/kvm/mmu/mmu.c
View File

@ -484,13 +484,15 @@ static bool spte_has_volatile_bits(u64 spte)
* also, it can help us to get a stable is_writable_pte()
* to ensure tlb flush is not missed.
*/
if (spte_can_locklessly_be_made_writable(spte) ||
is_access_track_spte(spte))
if (!is_writable_pte(spte) && is_mmu_writable_spte(spte))
return true;
if (is_access_track_spte(spte))
return true;
if (spte_ad_enabled(spte)) {
if ((spte & shadow_accessed_mask) == 0 ||
(is_writable_pte(spte) && (spte & shadow_dirty_mask) == 0))
if (!(spte & shadow_accessed_mask) ||
(is_writable_pte(spte) && !(spte & shadow_dirty_mask)))
return true;
}
@ -557,7 +559,7 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte)
* we always atomically update it, see the comments in
* spte_has_volatile_bits().
*/
if (spte_can_locklessly_be_made_writable(old_spte) &&
if (is_mmu_writable_spte(old_spte) &&
!is_writable_pte(new_spte))
flush = true;
@ -1187,7 +1189,7 @@ static bool spte_write_protect(u64 *sptep, bool pt_protect)
u64 spte = *sptep;
if (!is_writable_pte(spte) &&
!(pt_protect && spte_can_locklessly_be_made_writable(spte)))
!(pt_protect && is_mmu_writable_spte(spte)))
return false;
rmap_printk("spte %p %llx\n", sptep, *sptep);
@ -3196,8 +3198,7 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
* be removed in the fast path only if the SPTE was
* write-protected for dirty-logging or access tracking.
*/
if (fault->write &&
spte_can_locklessly_be_made_writable(spte)) {
if (fault->write && is_mmu_writable_spte(spte)) {
new_spte |= PT_WRITABLE_MASK;
/*

2
arch/x86/kvm/mmu/spte.h
View File

@ -390,7 +390,7 @@ static inline void check_spte_writable_invariants(u64 spte)
"kvm: Writable SPTE is not MMU-writable: %llx", spte);
}
static inline bool spte_can_locklessly_be_made_writable(u64 spte)
static inline bool is_mmu_writable_spte(u64 spte)
{
return spte & shadow_mmu_writable_mask;
}