KVM: X86: Implement call-back to propagate virtual_tsc_khz

This patch implements a call-back into the architecture code
to allow the propagation of changes to the virtual tsc_khz
of the vcpu.
On SVM it updates the tsc_ratio variable, on VMX it does
nothing.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 83015009995..a39fde4f5fe 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -885,6 +885,38 @@ static u64 svm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
 	return _tsc;
 }
 
+static void svm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+	u64 ratio;
+	u64 khz;
+
+	/* TSC scaling supported? */
+	if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR))
+		return;
+
+	/* TSC-Scaling disabled or guest TSC same frequency as host TSC? */
+	if (user_tsc_khz == 0) {
+		vcpu->arch.virtual_tsc_khz = 0;
+		svm->tsc_ratio = TSC_RATIO_DEFAULT;
+		return;
+	}
+
+	khz = user_tsc_khz;
+
+	/* TSC scaling required  - calculate ratio */
+	ratio = khz << 32;
+	do_div(ratio, tsc_khz);
+
+	if (ratio == 0 || ratio & TSC_RATIO_RSVD) {
+		WARN_ONCE(1, "Invalid TSC ratio - virtual-tsc-khz=%u\n",
+				user_tsc_khz);
+		return;
+	}
+	vcpu->arch.virtual_tsc_khz = user_tsc_khz;
+	svm->tsc_ratio             = ratio;
+}
+
 static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -4159,6 +4191,7 @@ static struct kvm_x86_ops svm_x86_ops = {
 
 	.has_wbinvd_exit = svm_has_wbinvd_exit,
 
+	.set_tsc_khz = svm_set_tsc_khz,
 	.write_tsc_offset = svm_write_tsc_offset,
 	.adjust_tsc_offset = svm_adjust_tsc_offset,