Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 512255a2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

Revert "sched/x86_64: Don't save flags on context switch" 



This reverts commit:

  2c7577a7 ("sched/x86_64: Don't save flags on context switch")

It was a nice speedup.  It's also not quite correct: SYSENTER
enables interrupts too early.

We can re-add this optimization once the SYSENTER code is beaten
into shape, which should happen in 4.3 or 4.4.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # v3.19
Link: http://lkml.kernel.org/r/85f56651f59f76624e80785a8fd3bdfdd089a818.1439838962.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2c6625cd

arch/x86/include/asm/switch_to.h

+4 −8
Original line number Diff line number Diff line
@@ -79,12 +79,12 @@ do { \ 
#else /* CONFIG_X86_32 */



/* frame pointer must be last for get_wchan */

#define SAVE_CONTEXT    "pushq %%rbp ; movq %%rsi,%%rbp\n\t"

#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp\t"

#define SAVE_CONTEXT    "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"

#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"



#define __EXTRA_CLOBBER  \

	, "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \

	  "r12", "r13", "r14", "r15", "flags"

	  "r12", "r13", "r14", "r15"



#ifdef CONFIG_CC_STACKPROTECTOR

#define __switch_canary							  \
@@ -100,11 +100,7 @@ do { \ 
#define __switch_canary_iparam

#endif	/* CC_STACKPROTECTOR */



/*

 * There is no need to save or restore flags, because flags are always

 * clean in kernel mode, with the possible exception of IOPL.  Kernel IOPL

 * has no effect.

 */

/* Save restore flags to clear handle leaking NT */

#define switch_to(prev, next, last) \

	asm volatile(SAVE_CONTEXT					  \

	     "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */	  \