From: Sean Christopherson Date: Sat, 13 Feb 2021 00:50:08 +0000 (-0800) Subject: KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=2855f98265dc579bd2becb79ce0156d08e0df813;p=linux.git KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect() 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 Message-Id: <20210213005015.1651772-8-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 0b55aa561ec8f..72b0928f2b2d9 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; }