linux-kernel - [PATCH 1/5] KVM: VMX: Restore host's MSR_IA32_RTIT

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Message-Id: <20210824110743.531127-2-xiaoyao.li@intel.com>
Date:   Tue, 24 Aug 2021 19:07:39 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Xiaoyao Li <xiaoyao.li@...el.com>,
        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
Subject: [PATCH 1/5] KVM: VMX: Restore host's MSR_IA32_RTIT_CTL when it's not zero

A minor optimation to WRMSR MSR_IA32_RTIT_CTL when necessary.

Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index fada1055f325..e0a9460e4dab 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1075,7 +1075,8 @@ static void pt_guest_exit(struct vcpu_vmx *vmx)
 	}
 
 	/* Reload host state (IA32_RTIT_CTL will be cleared on VM exit). */
-	wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
+	if (vmx->pt_desc.host.ctl)
+		wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
 }
 
 void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,
-- 
2.27.0