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, 3 insertions, 3 deletions

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 782c3a362ec6..c1b0a11033a2 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -99,7 +99,7 @@ int save_i387_xstate(void __user *buf)
                 if (err)
                         return err;
 
-                if (task_thread_info(tsk)->status & TS_XSAVE)
+                if (use_xsave())
                         err = xsave_user(buf);
                 else
                         err = fxsave_user(buf);
@@ -116,7 +116,7 @@ int save_i387_xstate(void __user *buf)
 
         clear_used_math(); /* trigger finit */
 
-        if (task_thread_info(tsk)->status & TS_XSAVE) {
+        if (use_xsave()) {
                 struct _fpstate __user *fx = buf;
                 struct _xstate __user *x = buf;
                 u64 xstate_bv;
@@ -225,7 +225,7 @@ int restore_i387_xstate(void __user *buf)
                 clts();
                 task_thread_info(current)->status |= TS_USEDFPU;
         }
-        if (task_thread_info(tsk)->status & TS_XSAVE)
+        if (use_xsave())
                 err = restore_user_xstate(buf);
         else
                 err = fxrstor_checking((__force struct i387_fxsave_struct *)