x86-64: move unlazy_fpu() into lazy cpu state part of context switch

Make sure that unlazy_fpu()'s stts gets batched along with the other
cpu state changes during context switch.  (32-bit already does this.)

This makes sure it gets batched when running paravirtualized.

[ Impact: optimise paravirtual FPU context switch ]
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/kernel/process_64.c

@@ -419,6 +419,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	load_TLS(next, cpu);
 
+	/* Must be after DS reload */
+	unlazy_fpu(prev_p);
+
 	/*
 	 * Leave lazy mode, flushing any hypercalls made here.
 	 * This must be done before restoring TLS segments so
@@ -459,9 +462,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 		wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
 	prev->gsindex = gsindex;
 
-	/* Must be after DS reload */
-	unlazy_fpu(prev_p);
-
 	/*
 	 * Switch the PDA and FPU contexts.
 	 */