Commit 988da782 authored by Yan Zhao's avatar Yan Zhao Committed by Sean Christopherson
Browse files

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



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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarYan Zhao <yan.y.zhao@intel.com>
Link: https://lore.kernel.org/r/20250318013238.5732-1-yan.y.zhao@intel.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent d17cc13c

arch/x86/kvm/mmu/tdp_mmu.c

+3 −1
Original line number Diff line number Diff line
@@ -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);