x86, xsave: context switch support using xsave/xrstor
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>
diff --git a/include/asm-x86/thread_info.h b/include/asm-x86/thread_info.h
index e64be88..30586f2 100644
--- a/include/asm-x86/thread_info.h
+++ b/include/asm-x86/thread_info.h
@@ -239,6 +239,7 @@
#define TS_POLLING 0x0004 /* true if in idle loop
and not sleeping */
#define TS_RESTORE_SIGMASK 0x0008 /* restore signal mask in do_signal() */
+#define TS_XSAVE 0x0010 /* Use xsave/xrstor */
#define tsk_is_polling(t) (task_thread_info(t)->status & TS_POLLING)