[PATCH 2/6] KVM: X86: Let kvm-clock report the right tsc frequency

[Joerg Roedel <joerg.roedel@xxxxxxx>]

This patch changes the kvm_guest_time_update function to use
TSC frequency the guest actually has for updating its clock.

Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |    2 ++
 arch/x86/kvm/svm.c              |    8 ++++++++
 arch/x86/kvm/vmx.c              |    6 ++++++
 arch/x86/kvm/x86.c              |   11 +++++++++--
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 35f81b1..16e7240 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -590,6 +590,8 @@ struct kvm_x86_ops {
 
 	void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 
+	bool (*use_virtual_tsc_khz)(struct kvm_vcpu *vcpu);
+
 	void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
 	const struct trace_print_flags *exit_reasons_str;
 };
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4e5da50..40ade85 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -914,6 +914,13 @@ static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
 	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 }
 
+static bool svm_use_virtual_tsc_khz(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	return svm->tsc_scale.enabled;
+}
+
 static void init_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -3996,6 +4003,7 @@ static struct kvm_x86_ops svm_x86_ops = {
 
 	.write_tsc_offset = svm_write_tsc_offset,
 	.adjust_tsc_offset = svm_adjust_tsc_offset,
+	.use_virtual_tsc_khz = svm_use_virtual_tsc_khz,
 
 	.set_tdp_cr3 = set_tdp_cr3,
 };
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1bdb49d..e0a6d4a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1174,6 +1174,11 @@ static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
 	vmcs_write64(TSC_OFFSET, offset + adjustment);
 }
 
+static bool vmx_use_virtual_tsc_khz(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 /*
  * Reads an msr value (of 'msr_index') into 'pdata'.
  * Returns 0 on success, non-0 otherwise.
@@ -4498,6 +4503,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
 
 	.write_tsc_offset = vmx_write_tsc_offset,
 	.adjust_tsc_offset = vmx_adjust_tsc_offset,
+	.use_virtual_tsc_khz = vmx_use_virtual_tsc_khz,
 
 	.set_tdp_cr3 = vmx_set_cr3,
 };
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1b8b16a..7979da4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -982,6 +982,14 @@ static inline int kvm_tsc_changes_freq(void)
 	return ret;
 }
 
+static u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu)
+{
+	if (kvm_x86_ops->use_virtual_tsc_khz(vcpu))
+		return vcpu->kvm->arch.virtual_tsc_khz;
+	else
+		return __this_cpu_read(cpu_tsc_khz);
+}
+
 static inline u64 nsec_to_cycles(u64 nsec)
 {
 	u64 ret;
@@ -1075,8 +1083,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 	local_irq_save(flags);
 	kvm_get_msr(v, MSR_IA32_TSC, &tsc_timestamp);
 	kernel_ns = get_kernel_ns();
-	this_tsc_khz = __this_cpu_read(cpu_tsc_khz);
-
+	this_tsc_khz = vcpu_tsc_khz(v);
 	if (unlikely(this_tsc_khz == 0)) {
 		local_irq_restore(flags);
 		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
-- 
1.7.1


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