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>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index 3580a7938a2e..38eb76156a47 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -1134,7 +1134,7 @@ asmlinkage void math_state_restore(void)
         /*
          * Paranoid restore. send a SIGSEGV if we fail to restore the state.
          */
-        if (unlikely(restore_fpu_checking(&me->thread.xstate->fxsave))) {
+        if (unlikely(restore_fpu_checking(me))) {
                 stts();
                 force_sig(SIGSEGV, me);
                 return;