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x86: Eliminate TS_XSAVE

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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>
This commit is contained in:
Avi Kivity
2010-05-06 11:45:45 +03:00
committed by H. Peter Anvin
parent 250825008f
commit c9ad488289
5 changed files with 21 additions and 16 deletions
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6
arch/x86/kernel/xsave.c
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@@ -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 *)