KVM: x86: Replace call-back compute_tsc_offset() with a common function

Both VMX and SVM calculate the tsc-offset in the same way, so this
patch removes the call-back compute_tsc_offset() and replaces it with a
common function kvm_compute_tsc_offset().
Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -856,7 +856,6 @@ struct kvm_x86_ops {
 	u64 (*read_tsc_offset)(struct kvm_vcpu *vcpu);
 	void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 
-	u64 (*compute_tsc_offset)(struct kvm_vcpu *vcpu, u64 target_tsc);
 	u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu, u64 host_tsc);
 
 	void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);

arch/x86/kvm/svm.c

@@ -1004,15 +1004,6 @@ static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho
 	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 }
 
-static u64 svm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
-{
-	u64 tsc;
-
-	tsc = kvm_scale_tsc(vcpu, rdtsc());
-
-	return target_tsc - tsc;
-}
-
 static void init_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -4370,7 +4361,6 @@ static struct kvm_x86_ops svm_x86_ops = {
 	.read_tsc_offset = svm_read_tsc_offset,
 	.write_tsc_offset = svm_write_tsc_offset,
 	.adjust_tsc_offset = svm_adjust_tsc_offset,
-	.compute_tsc_offset = svm_compute_tsc_offset,
 	.read_l1_tsc = svm_read_l1_tsc,
 
 	.set_tdp_cr3 = set_tdp_cr3,

arch/x86/kvm/vmx.c

@@ -2426,11 +2426,6 @@ static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho
 					   offset + adjustment);
 }
 
-static u64 vmx_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
-{
-	return target_tsc - rdtsc();
-}
-
 static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 1, 0);
@@ -10813,7 +10808,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
 	.read_tsc_offset = vmx_read_tsc_offset,
 	.write_tsc_offset = vmx_write_tsc_offset,
 	.adjust_tsc_offset = vmx_adjust_tsc_offset,
-	.compute_tsc_offset = vmx_compute_tsc_offset,
 	.read_l1_tsc = vmx_read_l1_tsc,
 
 	.set_tdp_cr3 = vmx_set_cr3,

arch/x86/kvm/x86.c

@@ -1392,6 +1392,15 @@ u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
 }
 EXPORT_SYMBOL_GPL(kvm_scale_tsc);
 
+static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
+{
+	u64 tsc;
+
+	tsc = kvm_scale_tsc(vcpu, rdtsc());
+
+	return target_tsc - tsc;
+}
+
 void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	struct kvm *kvm = vcpu->kvm;
@@ -1403,7 +1412,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
 	u64 data = msr->data;
 
 	raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
-	offset = kvm_x86_ops->compute_tsc_offset(vcpu, data);
+	offset = kvm_compute_tsc_offset(vcpu, data);
 	ns = get_kernel_ns();
 	elapsed = ns - kvm->arch.last_tsc_nsec;
 
@@ -1460,7 +1469,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		} else {
 			u64 delta = nsec_to_cycles(vcpu, elapsed);
 			data += delta;
-			offset = kvm_x86_ops->compute_tsc_offset(vcpu, data);
+			offset = kvm_compute_tsc_offset(vcpu, data);
 			pr_debug("kvm: adjusted tsc offset by %llu\n", delta);
 		}
 		matched = true;
@@ -2687,7 +2696,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		if (tsc_delta < 0)
 			mark_tsc_unstable("KVM discovered backwards TSC");
 		if (check_tsc_unstable()) {
-			u64 offset = kvm_x86_ops->compute_tsc_offset(vcpu,
+			u64 offset = kvm_compute_tsc_offset(vcpu,
 						vcpu->arch.last_guest_tsc);
 			kvm_x86_ops->write_tsc_offset(vcpu, offset);
 			vcpu->arch.tsc_catchup = 1;