linux-kernel - [PATCH 4/6] KVM: SVM: Propagate requested TSC frequency on vcpu init

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Date:	Wed, 9 Feb 2011 18:29:42 +0100
From:	Joerg Roedel <joerg.roedel@....com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>
CC:	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zamsden@...hat.com>,
	Joerg Roedel <joerg.roedel@....com>
Subject: [PATCH 4/6] KVM: SVM: Propagate requested TSC frequency on vcpu init

This patch implements the propagation of the VM
virtual_tsc_khz into each vcpu data-structure to enable the
tsc-scaling feature.

Signed-off-by: Joerg Roedel <joerg.roedel@....com>
---
 arch/x86/kvm/svm.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f51f757..29833a7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -879,6 +879,35 @@ static u64 svm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
 	return _tsc;
 }
 
+static bool svm_vcpu_init_tsc(struct kvm *kvm, struct vcpu_svm *svm)
+{
+	u64 raw_tsc, tsc, new_tsc;
+	u64 ratio;
+	u64 khz;
+
+	/* TSC scaling supported? */
+	if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR))
+		goto out;
+
+	/* Guest tsc same frequency as host tsc? */
+	if (kvm->arch.virtual_tsc_khz == tsc_khz)
+		goto out;
+
+	khz = kvm->arch.virtual_tsc_khz;
+
+	/* TSC scaling required  - calculate ratio */
+	ratio = khz << 32;
+	do_div(ratio, tsc_khz);
+	if (ratio == 0 || ratio & TSC_RATIO_RSVD)
+		return false;
+
+	svm->tsc_scale.ratio   = ratio;
+	svm->tsc_scale.enabled = true;
+
+out:
+	return true;
+}
+
 static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -1084,6 +1113,9 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
 	if (err)
 		goto free_svm;
 
+	if (!svm_vcpu_init_tsc(kvm, svm))
+		goto uninit;
+
 	err = -ENOMEM;
 	page = alloc_page(GFP_KERNEL);
 	if (!page)
-- 
1.7.1


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