]> git.ipfire.org Git - thirdparty/linux.git/commitdiff
KVM: x86/tdp_mmu: WARN if PFN changes for spurious faults
authorYan Zhao <yan.y.zhao@intel.com>
Tue, 18 Mar 2025 01:32:38 +0000 (09:32 +0800)
committerSean Christopherson <seanjc@google.com>
Mon, 28 Apr 2025 18:03:06 +0000 (11:03 -0700)
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>
arch/x86/kvm/mmu/tdp_mmu.c

index d16e3e6e46a5105e05ee94fcc3a4666da98a7024..1e2db49174594c45c93ecd7ef940efe42a63d53a 100644 (file)
@@ -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);