linux-kernel - [PATCH 2/2] KVM: VMX: Use x2apic_mode to avoid RDMSR when querying PI state

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Message-Id: <20210115220354.434807-3-seanjc@google.com>
Date:   Fri, 15 Jan 2021 14:03:54 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, luferry <luferry@....com>
Subject: [PATCH 2/2] KVM: VMX: Use x2apic_mode to avoid RDMSR when querying PI state

Use x2apic_mode instead of x2apic_enabled() when adjusting the
destination ID during Posted Interrupt updates.  This avoids the costly
RDMSR that is hidden behind x2apic_enabled().

Reported-by: luferry <luferry@....com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/posted_intr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index f02962dcc72c..4831bc44ce66 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -54,7 +54,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
 
 		dest = cpu_physical_id(cpu);
 
-		if (x2apic_enabled())
+		if (x2apic_mode)
 			new.ndst = dest;
 		else
 			new.ndst = (dest << 8) & 0xFF00;
@@ -104,7 +104,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
 
 		dest = cpu_physical_id(vcpu->cpu);
 
-		if (x2apic_enabled())
+		if (x2apic_mode)
 			new.ndst = dest;
 		else
 			new.ndst = (dest << 8) & 0xFF00;
@@ -174,7 +174,7 @@ int pi_pre_block(struct kvm_vcpu *vcpu)
 		 */
 		dest = cpu_physical_id(vcpu->pre_pcpu);
 
-		if (x2apic_enabled())
+		if (x2apic_mode)
 			new.ndst = dest;
 		else
 			new.ndst = (dest << 8) & 0xFF00;
-- 
2.30.0.284.gd98b1dd5eaa7-goog