Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Wanpeng Li <kernellwp@gmail.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Subject: [PATCH 1/3] KVM: X86: Delay read msr data iff writes ICR MSR
Date:   Thu, 26 Mar 2020 10:20:00 +0800
Message-Id: <1585189202-1708-2-git-send-email-wanpengli@tencent.com>
In-Reply-To: <1585189202-1708-1-git-send-email-wanpengli@tencent.com>
References: <1585189202-1708-1-git-send-email-wanpengli@tencent.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Wanpeng Li <wanpengli@tencent.com>

Delay read msr data until we identify guest accesses ICR MSR to avoid
to penalize all other MSR writes.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3156e25..9232b15 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1568,11 +1568,12 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
 enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
 {
 	u32 msr = kvm_rcx_read(vcpu);
-	u64 data = kvm_read_edx_eax(vcpu);
+	u64 data;
 	int ret = 0;
 
 	switch (msr) {
 	case APIC_BASE_MSR + (APIC_ICR >> 4):
+		data = kvm_read_edx_eax(vcpu);
 		ret = handle_fastpath_set_x2apic_icr_irqoff(vcpu, data);
 		break;
 	default:
-- 
2.7.4