From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Gardon <bgardon@google.com>,
Makarand Sonare <makarandsonare@google.com>
Subject: [PATCH 07/14] KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect()
Date: Fri, 12 Feb 2021 16:50:08 -0800 [thread overview]
Message-ID: <20210213005015.1651772-8-seanjc@google.com> (raw)
In-Reply-To: <20210213005015.1651772-1-seanjc@google.com>
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@google.com>
---
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
next prev parent reply other threads:[~2021-02-13 0:53 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-13 0:50 [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-13 0:50 ` [PATCH 01/14] KVM: x86/mmu: Expand collapsible SPTE zap for TDP MMU to ZONE_DEVICE pages Sean Christopherson
2021-02-18 12:36 ` Paolo Bonzini
2021-02-13 0:50 ` [PATCH 02/14] KVM: x86/mmu: Don't unnecessarily write-protect small pages in TDP MMU Sean Christopherson
2021-02-13 0:50 ` [PATCH 03/14] KVM: x86/mmu: Split out max mapping level calculation to helper Sean Christopherson
2021-02-13 0:50 ` [PATCH 04/14] KVM: x86/mmu: Pass the memslot to the rmap callbacks Sean Christopherson
2021-02-13 0:50 ` [PATCH 05/14] KVM: x86/mmu: Consult max mapping level when zapping collapsible SPTEs Sean Christopherson
2021-02-18 12:43 ` Paolo Bonzini
2021-02-18 16:23 ` Sean Christopherson
2021-02-18 22:30 ` Mike Kravetz
2021-02-19 1:31 ` Sean Christopherson
2021-02-13 0:50 ` [PATCH 06/14] KVM: nVMX: Disable PML in hardware when running L2 Sean Christopherson
2021-02-13 0:50 ` Sean Christopherson [this message]
2021-02-13 0:50 ` [PATCH 08/14] KVM: x86/mmu: Make dirty log size hook (PML) a value, not a function Sean Christopherson
2021-02-18 12:45 ` Paolo Bonzini
2021-02-13 0:50 ` [PATCH 09/14] KVM: x86: Move MMU's PML logic to common code Sean Christopherson
2021-02-13 0:50 ` [PATCH 10/14] KVM: x86: Further clarify the logic and comments for toggling log dirty Sean Christopherson
2021-02-18 12:50 ` Paolo Bonzini
2021-02-18 16:15 ` Sean Christopherson
2021-02-18 16:56 ` Paolo Bonzini
2021-02-13 0:50 ` [PATCH 11/14] KVM: VMX: Dynamically enable/disable PML based on memslot dirty logging Sean Christopherson
2021-02-13 0:50 ` [PATCH 12/14] KVM: x86/mmu: Don't set dirty bits when disabling dirty logging w/ PML Sean Christopherson
2021-02-18 17:08 ` Paolo Bonzini
2021-02-13 0:50 ` [PATCH 13/14] KVM: x86: Fold "write-protect large" use case into generic write-protect Sean Christopherson
2021-02-13 0:50 ` [PATCH 14/14] KVM: x86/mmu: Remove a variety of unnecessary exports Sean Christopherson
2021-02-17 22:50 ` [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements Sean Christopherson
2021-02-18 12:57 ` Paolo Bonzini
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