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@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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 72b0928f2b2d..ec4fc28b325a 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -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)
{
/*
- * 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);
--
2.30.1.766.gb4fecdf3b7-goog
