linux-kernel - [PATCH 11/12] KVM: VMX: Use a scaled host TSC for guest readings of MSR_IA32

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Message-Id: <1443418691-24050-12-git-send-email-haozhong.zhang@intel.com>
Date:	Mon, 28 Sep 2015 13:38:10 +0800
From:	Haozhong Zhang <haozhong.zhang@...el.com>
To:	kvm@...r.kernel.org
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Joerg Roedel <joro@...tes.org>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	Mihai Donțu <mdontu@...defender.com>,
	Andy Lutomirski <luto@...nel.org>,
	Kai Huang <kai.huang@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Haozhong Zhang <haozhong.zhang@...el.com>
Subject: [PATCH 11/12] KVM: VMX: Use a scaled host TSC for guest readings of MSR_IA32_TSC

This patch makes kvm-intel to return a scaled host TSC plus the TSC
offset when handling guest readings to MSR_IA32_TSC.

Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
---
 arch/x86/kvm/vmx.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e282eb8..d0a2928 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2245,15 +2245,15 @@ static void setup_msrs(struct vcpu_vmx *vmx)
 
 /*
  * reads and returns guest's timestamp counter "register"
- * guest_tsc = host_tsc + tsc_offset    -- 21.3
+ * guest_tsc = (host_tsc * tsc multiplier) >> 48 + tsc_offset
  */
-static u64 guest_read_tsc(void)
+static u64 guest_read_tsc(struct kvm_vcpu *vcpu)
 {
 	u64 host_tsc, tsc_offset;
 
 	host_tsc = rdtsc();
 	tsc_offset = vmcs_read64(TSC_OFFSET);
-	return host_tsc + tsc_offset;
+	return kvm_scale_tsc(vcpu, host_tsc) + tsc_offset;
 }
 
 /*
@@ -2636,7 +2636,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_EFER:
 		return kvm_get_msr_common(vcpu, msr_info);
 	case MSR_IA32_TSC:
-		msr_info->data = guest_read_tsc();
+		msr_info->data = guest_read_tsc(vcpu);
 		break;
 	case MSR_IA32_SYSENTER_CS:
 		msr_info->data = vmcs_read32(GUEST_SYSENTER_CS);
-- 
2.4.8

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