From: Yan Zhao Date: Tue, 18 Mar 2025 01:31:11 +0000 (+0800) Subject: KVM: x86/mmu: Further check old SPTE is leaf for spurious prefetch fault X-Git-Tag: v6.16-rc1~78^2~8^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ea9fcdf76d3d1d659fb3daaa0cca7b1f4a0697bc;p=thirdparty%2Flinux.git KVM: x86/mmu: Further check old SPTE is leaf for spurious prefetch fault Instead of simply treating a prefetch fault as spurious when there's a shadow-present old SPTE, further check if the old SPTE is leaf to determine if a prefetch fault is spurious. It's not reasonable to treat a prefetch fault as spurious when there's a shadow-present non-leaf SPTE without a corresponding shadow-present leaf SPTE. e.g., in the following sequence, a prefetch fault should not be considered spurious: 1. add a memslot with size 4K 2. prefault GPA A in the memslot 3. delete the memslot (zap all disabled) 4. re-add the memslot with size 2M 5. prefault GPA A again. In step 5, the prefetch fault attempts to install a 2M huge entry. Since step 3 zaps the leaf SPTE for GPA A while keeping the non-leaf SPTE, the leaf entry will remain empty after step 5 if the fetch fault is regarded as spurious due to a shadow-present non-leaf SPTE. Signed-off-by: Yan Zhao Link: https://lore.kernel.org/r/20250318013111.5648-1-yan.y.zhao@intel.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index a284dce227a08..b50d9e715806a 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3020,7 +3020,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, } if (is_shadow_present_pte(*sptep)) { - if (prefetch) + if (prefetch && is_last_spte(*sptep, level)) return RET_PF_SPURIOUS; /* diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 405874f4d0880..f534022572178 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1153,7 +1153,8 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, if (WARN_ON_ONCE(sp->role.level != fault->goal_level)) return RET_PF_RETRY; - if (fault->prefetch && is_shadow_present_pte(iter->old_spte)) + if (fault->prefetch && is_shadow_present_pte(iter->old_spte) && + is_last_spte(iter->old_spte, iter->level)) return RET_PF_SPURIOUS; if (is_shadow_present_pte(iter->old_spte) &&