x86: Eliminate TS_XSAVE

The fpu code currently uses current->thread_info->status & TS_XSAVE as
a way to distinguish between XSAVE capable processors and older processors.
The decision is not really task specific; instead we use the task status to
avoid a global memory reference - the value should be the same across all
threads.

Eliminate this tie-in into the task structure by using an alternative
instruction keyed off the XSAVE cpu feature; this results in shorter and
faster code, without introducing a global memory reference.

[ hpa: in the future, this probably should use an asm jmp ]

Signed-off-by: Avi Kivity <avi@redhat.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1273135546-29690-2-git-send-email-avi@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 1 insertions, 4 deletions

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 54c31c285488..14ca1dc7a703 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -102,10 +102,7 @@ void __cpuinit fpu_init(void)
 
         mxcsr_feature_mask_init();
         /* clean state in init */
-        if (cpu_has_xsave)
-                current_thread_info()->status = TS_XSAVE;
-        else
-                current_thread_info()->status = 0;
+        current_thread_info()->status = 0;
         clear_used_math();
 }
 #endif  /* CONFIG_X86_64 */