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From: Mingwei Zhang <mizhang@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>,
	Mingwei Zhang <mizhang@google.com>,
	Jing Zhang <jingzhangos@google.com>,
	David Matlack <dmatlack@google.com>
Subject: [PATCH v3 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set_spte
Date: Fri, 30 Jul 2021 15:59:37 -0700	[thread overview]
Message-ID: <20210730225939.3852712-2-mizhang@google.com> (raw)
In-Reply-To: <20210730225939.3852712-1-mizhang@google.com>

Drop an unnecessary is_shadow_present_pte() check when updating the rmaps
after installing a non-MMIO SPTE.  set_spte() is used only to create
shadow-present SPTEs, e.g. MMIO SPTEs are handled early on, mmu_set_spte()
runs with mmu_lock held for write, i.e. the SPTE can't be zapped between
writing the SPTE and updating the rmaps.

Opportunistically combine the "new SPTE" logic for large pages and rmaps.

No functional change intended.

Suggested-by: Ben Gardon <bgardon@google.com>

Reviewed-by: Ben Gardon <bgardon@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b888385d1933..442cc554ebd6 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2690,15 +2690,13 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 
 	pgprintk("%s: setting spte %llx\n", __func__, *sptep);
 	trace_kvm_mmu_set_spte(level, gfn, sptep);
-	if (!was_rmapped && is_large_pte(*sptep))
-		++vcpu->kvm->stat.lpages;
 
-	if (is_shadow_present_pte(*sptep)) {
-		if (!was_rmapped) {
-			rmap_count = rmap_add(vcpu, sptep, gfn);
-			if (rmap_count > RMAP_RECYCLE_THRESHOLD)
-				rmap_recycle(vcpu, sptep, gfn);
-		}
+	if (!was_rmapped) {
+		if (is_large_pte(*sptep))
+			++vcpu->kvm->stat.lpages;
+		rmap_count = rmap_add(vcpu, sptep, gfn);
+		if (rmap_count > RMAP_RECYCLE_THRESHOLD)
+			rmap_recycle(vcpu, sptep, gfn);
 	}
 
 	return ret;
-- 
2.32.0.554.ge1b32706d8-goog


  reply	other threads:[~2021-07-30 22:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 22:59 [PATCH v3 0/3] Add detailed page size stats in KVM stats Mingwei Zhang
2021-07-30 22:59 ` Mingwei Zhang [this message]
2021-08-02 22:29   ` [PATCH v3 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set_spte David Matlack
2021-07-30 22:59 ` [PATCH v3 2/3] KVM: x86/mmu: Avoid collision with !PRESENT SPTEs in TDP MMU lpage stats Mingwei Zhang
2021-08-02 22:40   ` David Matlack
2021-07-30 22:59 ` [PATCH v3 3/3] KVM: x86/mmu: Add detailed page size stats Mingwei Zhang
2021-08-02 22:41   ` David Matlack
2021-08-02 23:02   ` Sean Christopherson
2021-08-02 23:45     ` Mingwei Zhang

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