x86: Introduce 'struct fpu' and related API

Currently all fpu state access is through tsk->thread.xstate.  Since we wish
to generalize fpu access to non-task contexts, wrap the state in a new
'struct fpu' and convert existing access to use an fpu API.

Signal frame handlers are not converted to the API since they will remain
task context only things.

Signed-off-by: Avi Kivity <avi@redhat.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1273135546-29690-3-git-send-email-avi@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index c1b0a11..37e68fc 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -109,7 +109,7 @@
 		task_thread_info(tsk)->status &= ~TS_USEDFPU;
 		stts();
 	} else {
-		if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
+		if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,
 				   xstate_size))
 			return -1;
 	}