From: Sean Christopherson seanjc@google.com
[ Upstream commit 44ac5958a6c1fd91ac8810fbb37194e377d78db5 ]
Check that PML is actually enabled before setting the mask to force a SPTE to be write-protected. The bits used for the !AD_ENABLED case are in the upper half of the SPTE. With 64-bit paging and EPT, these bits are ignored, but with 32-bit PAE paging they are reserved. Setting them for L2 SPTEs without checking PML breaks NPT on 32-bit KVM.
Fixes: 1f4e5fc83a42 ("KVM: x86: fix nested guest live migration with PML") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20210225204749.1512652-2-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/mmu/mmu_internal.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 8404145fb179..cf101b73a360 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -76,15 +76,15 @@ static inline struct kvm_mmu_page *sptep_to_sp(u64 *sptep) static inline bool kvm_vcpu_ad_need_write_protect(struct kvm_vcpu *vcpu) { /* - * When using the EPT page-modification log, the GPAs in the log - * would come from L2 rather than L1. Therefore, we need to rely - * on write protection to record dirty pages. This also bypasses - * PML, since writes now result in a vmexit. Note, this helper will - * tag SPTEs as needing write-protection even if PML is disabled or - * unsupported, but that's ok because the tag is consumed if and only - * if PML is enabled. Omit the PML check to save a few uops. + * When using the EPT page-modification log, the GPAs in the CPU dirty + * log would come from L2 rather than L1. Therefore, we need to rely + * on write protection to record dirty pages, which bypasses PML, since + * writes now result in a vmexit. Note, the check on CPU dirty logging + * being enabled is mandatory as the bits used to denote WP-only SPTEs + * are reserved for NPT w/ PAE (32-bit KVM). */ - return vcpu->arch.mmu == &vcpu->arch.guest_mmu; + return vcpu->arch.mmu == &vcpu->arch.guest_mmu && + kvm_x86_ops.cpu_dirty_log_size; }
bool is_nx_huge_page_enabled(void);