On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Prioritize private vs. shared gfn attribute checks above slot validity
checks to ensure a consistent userspace ABI. E.g. as is, KVM will exit to
userspace if there is no memslot, but emulate accesses to the APIC access
page even if the attributes mismatch.
Fixes: 8dd2eee9d526 ("KVM: x86/mmu: Handle page fault for private memory")
Cc: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Cc: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
Cc: Fuad Tabba <tabba@xxxxxxxxxx>
Cc: Michael Roth <michael.roth@xxxxxxx>
Cc: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
Message-ID: <20240228024147.41573-10-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
--- arch/x86/kvm/mmu/mmu.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 0d884d0b0f35..ba50b93e93ed 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4317,11 +4317,6 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault return RET_PF_EMULATE; }- if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {- kvm_mmu_prepare_memory_fault_exit(vcpu, fault); - return -EFAULT; - } - if (fault->is_private) return kvm_faultin_pfn_private(vcpu, fault);@@ -4359,9 +4354,24 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,{ int ret;+ /*+ * Note that the mmu_invalidate_seq also serves to detect a concurrent + * change in attributes. is_page_fault_stale() will detect an + * invalidation relate to fault->fn and resume the guest without
s/fault->fn/fault->gfn/
+ * installing a mapping in the page tables. + */ fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq; smp_rmb();+ /*+ * Now that we have a snapshot of mmu_invalidate_seq we can check for a + * private vs. shared mismatch. + */ + if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) { + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); + return -EFAULT; + } + /* * Check for a relevant mmu_notifier invalidation event before getting * the pfn from the primary MMU, and before acquiring mmu_lock.
