Expand the comment about need to use write-protection for nested EPT when PML is enabled to clarify that the tagging is a nop when PML is _not_ enabled. Without the clarification, omitting the PML check looks wrong at first^Wfifth glance. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/mmu/mmu_internal.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 0b55aa561ec8..72b0928f2b2d 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -84,7 +84,10 @@ 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. + * 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. */ return vcpu->arch.mmu == &vcpu->arch.guest_mmu; } -- 2.30.0.478.g8a0d178c01-goog
