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KVM: x86/tdp_mmu: WARN if PFN changes for spurious faults

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Add a WARN() to assert that KVM does _not_ change the PFN of a
shadow-present SPTE during spurious fault handling.

KVM should _never_ change the PFN of a shadow-present SPTE and TDP MMU
already BUG()s on this. However, spurious faults just return early before
the existing BUG() could be hit.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Link: https://lore.kernel.org/r/20250318013238.5732-1-yan.y.zhao@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yan Zhao 2025-03-18 09:32:38 +08:00 committed by Sean Christopherson
parent d17cc13cc4
commit 988da78202
1 changed files with 3 additions and 1 deletions
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4
arch/x86/kvm/mmu/tdp_mmu.c
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@ -1155,8 +1155,10 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
if (is_shadow_present_pte(iter->old_spte) &&
(fault->prefetch || is_access_allowed(fault, iter->old_spte)) &&
is_last_spte(iter->old_spte, iter->level))
is_last_spte(iter->old_spte, iter->level)) {
WARN_ON_ONCE(fault->pfn != spte_to_pfn(iter->old_spte));
return RET_PF_SPURIOUS;
}
if (unlikely(!fault->slot))
new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);