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@xxxxxxxxxx>
Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 6365eb6c1390..d219ecd4ac5b 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1139,8 +1139,10 @@ 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);
--
2.43.2
