From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752731AbbHSHKV (ORCPT ); Wed, 19 Aug 2015 03:10:21 -0400 Received: from terminus.zytor.com ([198.137.202.10]:46662 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752395AbbHSHKT (ORCPT ); Wed, 19 Aug 2015 03:10:19 -0400 Date: Wed, 19 Aug 2015 00:09:31 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, luto@kernel.org, hpa@zytor.com, mingo@kernel.org, linux-kernel@vger.kernel.org Reply-To: tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, luto@kernel.org, hpa@zytor.com, mingo@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <85f56651f59f76624e80785a8fd3bdfdd089a818.1439838962.git.luto@kernel.org> References: <85f56651f59f76624e80785a8fd3bdfdd089a818.1439838962.git.luto@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] Revert "sched/x86_64: Don' t save flags on context switch" Git-Commit-ID: 512255a2ad2c832ca7d4de9f31245f73781922d0 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 512255a2ad2c832ca7d4de9f31245f73781922d0 Gitweb: http://git.kernel.org/tip/512255a2ad2c832ca7d4de9f31245f73781922d0 Author: Andy Lutomirski AuthorDate: Mon, 17 Aug 2015 12:22:50 -0700 Committer: Ingo Molnar 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 Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org # v3.19 Link: http://lkml.kernel.org/r/85f56651f59f76624e80785a8fd3bdfdd089a818.1439838962.git.luto@kernel.org Signed-off-by: Ingo Molnar --- 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 */ \