x86, fpu: split FPU state from task struct - v5

Split the FPU save area from the task struct. This allows easy migration
of FPU context, and it's generally cleaner. It also allows the following
two optimizations:

1) only allocate when the application actually uses FPU, so in the first
lazy FPU trap. This could save memory for non-fpu using apps. Next patch
does this lazy allocation.

2) allocate the right size for the actual cpu rather than 512 bytes always.
Patches enabling xsave/xrstor support (coming shortly) will take advantage
of this.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index 6d883b13ef4f..dc0cb497eec3 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -1128,7 +1128,7 @@ asmlinkage void math_state_restore(void)
 
         if (!used_math())
                 init_fpu(me);
-        restore_fpu_checking(&me->thread.i387.fxsave);
+        restore_fpu_checking(&me->thread.xstate->fxsave);
         task_thread_info(me)->status |= TS_USEDFPU;
         me->fpu_counter++;
 }
@@ -1164,6 +1164,10 @@ void __init trap_init(void)
 #endif
        
         /*
+         * initialize the per thread extended state:
+         */
+        init_thread_xstate();
+        /*
          * Should be a barrier for any external CPU state.
          */
         cpu_init();