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| Started by | Andy Lutomirski <luto@kernel.org> |
|---|---|
| First post | 2015-08-17 21:30 +0200 |
| Last post | 2015-08-19 09:20 +0200 |
| Articles | 2 — 2 participants |
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[PATCH 1/3] Revert "sched/x86_64: Don't save flags on context switch" Andy Lutomirski <luto@kernel.org> - 2015-08-17 21:30 +0200
[tip:x86/asm] Revert "sched/x86_64: Don' t save flags on context switch" tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2015-08-19 09:20 +0200
| From | Andy Lutomirski <luto@kernel.org> |
|---|---|
| Date | 2015-08-17 21:30 +0200 |
| Subject | [PATCH 1/3] Revert "sched/x86_64: Don't save flags on context switch" |
| Message-ID | <pYygy-8f8-33@gated-at.bofh.it> |
This reverts commit 2c7577a7583747c9b71f26dced7f696b739da745.
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.
Cc: stable@vger.kernel.org # v3.19
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/switch_to.h | 12 ++++--------
1 file 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 */ \
--
2.4.3
--
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| From | tip-bot for Andy Lutomirski <tipbot@zytor.com> |
|---|---|
| Date | 2015-08-19 09:20 +0200 |
| Subject | [tip:x86/asm] Revert "sched/x86_64: Don' t save flags on context switch" |
| Message-ID | <pZ5Pb-7hG-3@gated-at.bofh.it> |
| In reply to | #1208829 |
Commit-ID: 512255a2ad2c832ca7d4de9f31245f73781922d0
Gitweb: http://git.kernel.org/tip/512255a2ad2c832ca7d4de9f31245f73781922d0
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Mon, 17 Aug 2015 12:22:50 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 18 Aug 2015 09:39:26 +0200
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>
---
arch/x86/include/asm/switch_to.h | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 751bf4b..d7f3b3b 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 */ \
--
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the body of a message to majordomo@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
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