[PATCH 1/6] KVM: SVM: Implement infrastructure for TSC_RATE_MSR

[Joerg Roedel <joerg.roedel@xxxxxxx>]

This patch enhances the kvm_amd module with functions to
support the TSC_RATE_MSR which can be used to set a given
tsc frequency for the guest vcpu.

Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
---
 arch/x86/include/asm/msr-index.h |    1 +
 arch/x86/kvm/svm.c               |   44 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index fd5a1f3..a7b3e40 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -114,6 +114,7 @@
    complete list. */
 
 #define MSR_AMD64_PATCH_LEVEL		0x0000008b
+#define MSR_AMD64_TSC_RATIO		0xc0000104
 #define MSR_AMD64_NB_CFG		0xc001001f
 #define MSR_AMD64_PATCH_LOADER		0xc0010020
 #define MSR_AMD64_OSVW_ID_LENGTH	0xc0010140
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2a19322..4e5da50 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -63,6 +63,8 @@ MODULE_LICENSE("GPL");
 
 #define DEBUGCTL_RESERVED_BITS (~(0x3fULL))
 
+#define TSC_RATIO_RSVD          0xffffff0000000000ULL
+
 static bool erratum_383_found __read_mostly;
 
 static const u32 host_save_user_msrs[] = {
@@ -144,6 +146,12 @@ struct vcpu_svm {
 	unsigned int3_injected;
 	unsigned long int3_rip;
 	u32 apf_reason;
+
+	struct {
+		bool enabled;
+		u64  ratio;
+	} tsc_scale;
+
 };
 
 #define MSR_INVALID			0xffffffffU
@@ -854,6 +862,32 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
 	seg->base = 0;
 }
 
+static u64 __scale_tsc(u64 ratio, u64 tsc)
+{
+	u64 mult, frac, _tsc;
+
+	mult  = ratio >> 32;
+	frac  = ratio & ((1ULL << 32) - 1);
+
+	_tsc  = tsc;
+	_tsc *= mult;
+	_tsc += (tsc >> 32) * frac;
+	_tsc += ((tsc & ((1ULL << 32) - 1)) * frac) >> 32;
+
+	return _tsc;
+}
+
+static u64 svm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+	u64 _tsc = tsc;
+
+	if (svm->tsc_scale.enabled)
+		_tsc = __scale_tsc(svm->tsc_scale.ratio, tsc);
+
+	return _tsc;
+}
+
 static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -1141,6 +1175,9 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 	for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
 		rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
+
+	if (static_cpu_has(X86_FEATURE_TSCRATEMSR) && svm->tsc_scale.enabled)
+		wrmsrl(MSR_AMD64_TSC_RATIO, svm->tsc_scale.ratio);
 }
 
 static void svm_vcpu_put(struct kvm_vcpu *vcpu)
@@ -1161,6 +1198,9 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
 #endif
 	for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
 		wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
+
+	if (static_cpu_has(X86_FEATURE_TSCRATEMSR) && svm->tsc_scale.enabled)
+		wrmsr(MSR_AMD64_TSC_RATIO, 0, 1);
 }
 
 static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
@@ -2813,7 +2853,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
 	case MSR_IA32_TSC: {
 		struct vmcb *vmcb = get_host_vmcb(svm);
 
-		*data = vmcb->control.tsc_offset + native_read_tsc();
+		*data = vmcb->control.tsc_offset +
+			svm_scale_tsc(vcpu, native_read_tsc());
+
 		break;
 	}
 	case MSR_STAR:
-- 
1.7.1


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