[PATCH 2/6] 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               |   37 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 5bfafb6..fdac548 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -106,6 +106,7 @@
    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 bfb4948..c96c0a6 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[] = {
@@ -142,6 +144,12 @@ struct vcpu_svm {
 	unsigned int3_injected;
 	unsigned long int3_rip;
 	u32 apf_reason;
+
+	struct {
+		bool enabled;
+		u64  ratio;
+	} tsc_scale;
+
 };
 
 #define MSR_INVALID			0xffffffffU
@@ -852,6 +860,25 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
 	seg->base = 0;
 }
 
+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) {
+		u64 mult, frac;
+
+		mult  = svm->tsc_scale.ratio >> 32;
+		frac  = svm->tsc_scale.ratio & ((1ULL << 32) - 1);
+
+		_tsc *= mult;
+		_tsc += (tsc >> 32) * frac;
+		_tsc += ((tsc & ((1ULL << 32) - 1)) * frac) >> 32;
+	}
+
+	return _tsc;
+}
+
 static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -2808,7 +2835,9 @@ 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:
@@ -3564,6 +3593,9 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	clgi();
 
+	if (static_cpu_has(X86_FEATURE_TSCRATEMSR) && svm->tsc_scale.enabled)
+		wrmsrl(MSR_AMD64_TSC_RATIO, svm->tsc_scale.ratio);
+
 	local_irq_enable();
 
 	asm volatile (
@@ -3647,6 +3679,9 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 
 	local_irq_disable();
 
+	if (static_cpu_has(X86_FEATURE_TSCRATEMSR) && svm->tsc_scale.enabled)
+		wrmsr(MSR_AMD64_TSC_RATIO, 0, 1);
+
 	vcpu->arch.cr2 = svm->vmcb->save.cr2;
 	vcpu->arch.regs[VCPU_REGS_RAX] = svm->vmcb->save.rax;
 	vcpu->arch.regs[VCPU_REGS_RSP] = svm->vmcb->save.rsp;
-- 
1.7.1


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