xen: 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.

I don't know much of xen code. But, since the code is in x86 architecture,
the percpu_xxx is exactly same as this_cpu_xxx serials functions. So, the
change is safe.

Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Christoph Lameter <cl@gentwo.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index 8bbb465..1573376 100644
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -26,7 +26,7 @@
 	struct vcpu_info *vcpu;
 	unsigned long flags;
 
-	vcpu = percpu_read(xen_vcpu);
+	vcpu = this_cpu_read(xen_vcpu);
 
 	/* flag has opposite sense of mask */
 	flags = !vcpu->evtchn_upcall_mask;
@@ -50,7 +50,7 @@
 	   make sure we're don't switch CPUs between getting the vcpu
 	   pointer and updating the mask. */
 	preempt_disable();
-	vcpu = percpu_read(xen_vcpu);
+	vcpu = this_cpu_read(xen_vcpu);
 	vcpu->evtchn_upcall_mask = flags;
 	preempt_enable_no_resched();
 
@@ -72,7 +72,7 @@
 	   make sure we're don't switch CPUs between getting the vcpu
 	   pointer and updating the mask. */
 	preempt_disable();
-	percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
+	this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
 	preempt_enable_no_resched();
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
@@ -86,7 +86,7 @@
 	   the caller is confused and is trying to re-enable interrupts
 	   on an indeterminate processor. */
 
-	vcpu = percpu_read(xen_vcpu);
+	vcpu = this_cpu_read(xen_vcpu);
 	vcpu->evtchn_upcall_mask = 0;
 
 	/* Doesn't matter if we get preempted here, because any