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x86, xsave: context switch support using xsave/xrstor

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Uses xsave/xrstor (instead of traditional fxsave/fxrstor) in context switch
when available.

Introduces TS_XSAVE flag, which determine the need to use xsave/xrstor
instructions during context switch instead of the legacy fxsave/fxrstor
instructions. Thread-synchronous status word is already in L1 cache during
this code patch and thus minimizes the performance penality compared to
(cpu_has_xsave) checks.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Suresh Siddha
2008-07-29 10:29:20 -07:00
committed by Ingo Molnar
parent dc1e35c6e9
commit b359e8a434
7 changed files with 103 additions and 8 deletions
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5
arch/x86/kernel/i387.c
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@@ -97,7 +97,10 @@ void __cpuinit fpu_init(void)
mxcsr_feature_mask_init();
/* clean state in init */
current_thread_info()->status = 0;
if (cpu_has_xsave)
current_thread_info()->status = TS_XSAVE;
else
current_thread_info()->status = 0;
clear_used_math();
}
#endif /* CONFIG_X86_64 */