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authorAndy Lutomirski <luto@kernel.org>2015-08-17 12:22:50 -0700
committerIngo Molnar <mingo@kernel.org>2015-08-18 09:39:26 +0200
commit512255a2ad2c832ca7d4de9f31245f73781922d0 (patch)
tree494fcca893dc7a02c04353f11a21a0672f527fb6 /arch
parent2c6625cd545bdd66acff14f3394865d43920a5c7 (diff)
downloadlinux-512255a2ad2c832ca7d4de9f31245f73781922d0.tar.bz2
Revert "sched/x86_64: Don't save flags on context switch"
This reverts commit: 2c7577a75837 ("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: Andy 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: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/switch_to.h12
1 files changed, 4 insertions, 8 deletions
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 751bf4b7bf11..d7f3b3b78ac3 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -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 */ \