x86-64: Move TLB state from PDA to per-cpu and consolidate with 32-bit.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 7bc7852..98cb986 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1063,11 +1063,7 @@
 	struct mm_struct *mm = info;
 	struct mm_struct *active_mm;
 
-#ifdef CONFIG_X86_64
-	active_mm = read_pda(active_mm);
-#else
-	active_mm = __get_cpu_var(cpu_tlbstate).active_mm;
-#endif
+	active_mm = percpu_read(cpu_tlbstate.active_mm);
 
 	if (active_mm == mm)
 		leave_mm(smp_processor_id());