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KVM: x86/mmu: Set SPTE_AD_WRPROT_ONLY_MASK if and only if PML is enabled 

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: 1f4e5fc83a ("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>
This commit is contained in:
Sean Christopherson 2021-02-25 12:47:26 -08:00 committed by Paolo Bonzini
parent 919f4ebc59
commit 44ac5958a6
1 changed files with 8 additions and 8 deletions
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16
arch/x86/kvm/mmu/mmu_internal.h
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@ -81,15 +81,15 @@ static inline struct kvm_mmu_page *sptep_to_sp(u64 *sptep)
static inline bool kvm_vcpu_ad_need_write_protect(struct kvm_vcpu *vcpu) 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 * When using the EPT page-modification log, the GPAs in the CPU dirty
* would come from L2 rather than L1. Therefore, we need to rely * log would come from L2 rather than L1. Therefore, we need to rely
* on write protection to record dirty pages. This also bypasses * on write protection to record dirty pages, which bypasses PML, since
* PML, since writes now result in a vmexit. Note, this helper will * writes now result in a vmexit. Note, the check on CPU dirty logging
* tag SPTEs as needing write-protection even if PML is disabled or * being enabled is mandatory as the bits used to denote WP-only SPTEs
* unsupported, but that's ok because the tag is consumed if and only * are reserved for NPT w/ PAE (32-bit KVM).
* if PML is enabled. Omit the PML check to save a few uops.
*/ */
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); bool is_nx_huge_page_enabled(void);