restore: Reserve space in restorer for FPU frame

For code simplicity we reserve the maximum size which
might be needed to form an FPU frame (ie for both
xsave and fxsave operations).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/restorer.h

@@ -80,6 +80,16 @@ struct thread_restore_args {
 	struct rst_sched_param		sp;
 
 	struct task_restore_core_args	*ta;
+
+	/*
+	 * The FPU xsave area must be continious and FP_MIN_ALIGN_BYTES
+	 * aligned, thus make sure the compiler won't insert any hole here.
+	 */
+	bool				has_fpu;
+	union {
+		struct xsave_struct	xsave;
+		unsigned char		__pad[sizeof(struct xsave_struct) + FP_XSTATE_MAGIC2_SIZE];
+	};
 } __aligned(sizeof(long));
 
 struct task_restore_core_args {