linux-kernel - [PATCH] KVM: avoid unnecessary bitmap clear ops

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Message-ID: <1571970281-20083-1-git-send-email-linmiaohe@huawei.com>
Date:   Fri, 25 Oct 2019 10:24:41 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <pbonzini@...hat.com>, <rkrcmar@...hat.com>,
        <sean.j.christopherson@...el.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <hpa@...or.com>
CC:     <x86@...nel.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH] KVM: avoid unnecessary bitmap clear ops

When set one bit in bitmap, there is no need to
clear it before.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 arch/x86/kvm/svm.c | 3 ++-
 arch/x86/kvm/x86.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ca200b50cde4..d997d011a942 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2044,9 +2044,10 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
 	entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
 
-	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
 	if (svm->avic_is_running)
 		entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
+	else
+		entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
 
 	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
 	avic_update_iommu_vcpu_affinity(vcpu, h_physical_id,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ff395f812719..9b535888ea90 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1036,9 +1036,10 @@ static void kvm_update_dr7(struct kvm_vcpu *vcpu)
 	else
 		dr7 = vcpu->arch.dr7;
 	kvm_x86_ops->set_dr7(vcpu, dr7);
-	vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
 	if (dr7 & DR7_BP_EN_MASK)
 		vcpu->arch.switch_db_regs |= KVM_DEBUGREG_BP_ENABLED;
+	else
+		vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
 }
 
 static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)
-- 
2.19.1