KVM: use this_cpu_xxx replace percpu_xxx funcs

percpu_xxx funcs are duplicated with this_cpu_xxx funcs, so replace them
for further code clean up.

And in preempt safe scenario, __this_cpu_xxx funcs has a bit better
performance since __this_cpu_xxx has no redundant preempt_disable()
Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/x86.c

@@ -4664,15 +4664,15 @@ static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
 
 static int kvm_is_in_guest(void)
 {
-	return percpu_read(current_vcpu) != NULL;
+	return __this_cpu_read(current_vcpu) != NULL;
 }
 
 static int kvm_is_user_mode(void)
 {
 	int user_mode = 3;
 
-	if (percpu_read(current_vcpu))
-		user_mode = kvm_x86_ops->get_cpl(percpu_read(current_vcpu));
+	if (__this_cpu_read(current_vcpu))
+		user_mode = kvm_x86_ops->get_cpl(__this_cpu_read(current_vcpu));
 
 	return user_mode != 0;
 }
@@ -4681,8 +4681,8 @@ static unsigned long kvm_get_guest_ip(void)
 {
 	unsigned long ip = 0;
 
-	if (percpu_read(current_vcpu))
-		ip = kvm_rip_read(percpu_read(current_vcpu));
+	if (__this_cpu_read(current_vcpu))
+		ip = kvm_rip_read(__this_cpu_read(current_vcpu));
 
 	return ip;
 }
@@ -4695,13 +4695,13 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = {
 
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu)
 {
-	percpu_write(current_vcpu, vcpu);
+	__this_cpu_write(current_vcpu, vcpu);
 }
 EXPORT_SYMBOL_GPL(kvm_before_handle_nmi);
 
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu)
 {
-	percpu_write(current_vcpu, NULL);
+	__this_cpu_write(current_vcpu, NULL);
 }
 EXPORT_SYMBOL_GPL(kvm_after_handle_nmi);