kvm: x86: encapsulate wrmsr(MSR_KVM_SYSTEM_TIME) emulation in helper fn

No functional change intended.
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Reviewed-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Change-Id: I7cbe71069db98d1ded612fd2ef088b70e7618426
Message-Id: <20200818152429.1923996-2-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -1948,6 +1948,34 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
 	kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
 }
 
+static void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,
+				  bool old_msr, bool host_initiated)
+{
+	struct kvm_arch *ka = &vcpu->kvm->arch;
+
+	if (vcpu->vcpu_id == 0 && !host_initiated) {
+		if (ka->boot_vcpu_runs_old_kvmclock && old_msr)
+			kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
+
+		ka->boot_vcpu_runs_old_kvmclock = old_msr;
+	}
+
+	vcpu->arch.time = system_time;
+	kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
+
+	/* we verify if the enable bit is set... */
+	vcpu->arch.pv_time_enabled = false;
+	if (!(system_time & 1))
+		return;
+
+	if (!kvm_gfn_to_hva_cache_init(vcpu->kvm,
+				       &vcpu->arch.pv_time, system_time & ~1ULL,
+				       sizeof(struct pvclock_vcpu_time_info)))
+		vcpu->arch.pv_time_enabled = true;
+
+	return;
+}
+
 static uint32_t div_frac(uint32_t dividend, uint32_t divisor)
 {
 	do_shl32_div32(dividend, divisor);
@@ -3093,33 +3121,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		kvm_write_wall_clock(vcpu->kvm, data);
 		break;
 	case MSR_KVM_SYSTEM_TIME_NEW:
-	case MSR_KVM_SYSTEM_TIME: {
-		struct kvm_arch *ka = &vcpu->kvm->arch;
-
-		if (vcpu->vcpu_id == 0 && !msr_info->host_initiated) {
-			bool tmp = (msr == MSR_KVM_SYSTEM_TIME);
-
-			if (ka->boot_vcpu_runs_old_kvmclock != tmp)
-				kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
-
-			ka->boot_vcpu_runs_old_kvmclock = tmp;
-		}
-
-		vcpu->arch.time = data;
-		kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu);
-
-		/* we verify if the enable bit is set... */
-		vcpu->arch.pv_time_enabled = false;
-		if (!(data & 1))
+		kvm_write_system_time(vcpu, data, false, msr_info->host_initiated);
 		break;
-
-		if (!kvm_gfn_to_hva_cache_init(vcpu->kvm,
-		     &vcpu->arch.pv_time, data & ~1ULL,
-		     sizeof(struct pvclock_vcpu_time_info)))
-			vcpu->arch.pv_time_enabled = true;
-
+	case MSR_KVM_SYSTEM_TIME:
+		kvm_write_system_time(vcpu, data, true, msr_info->host_initiated);
 		break;
-	}
 	case MSR_KVM_ASYNC_PF_EN:
 		if (kvm_pv_enable_async_pf(vcpu, data))
 			return 1;