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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index ebefb5407b9d36f5ccbb1c458708fb8a647ff19b..c9b8904736db3079c28012339858912ea0281293 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/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.
         */