From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220AbbEQGFO (ORCPT ); Sun, 17 May 2015 02:05:14 -0400 Received: from terminus.zytor.com ([198.137.202.10]:53862 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751208AbbEQGFD (ORCPT ); Sun, 17 May 2015 02:05:03 -0400 Date: Sat, 16 May 2015 23:04:05 -0700 From: tip-bot for Denys Vlasenko Message-ID: Cc: peterz@infradead.org, mingo@kernel.org, hpa@zytor.com, brgerst@gmail.com, ast@plumgrid.com, luto@amacapital.net, fweisbec@gmail.com, torvalds@linux-foundation.org, bp@alien8.de, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, rostedt@goodmis.org, oleg@redhat.com, wad@chromium.org, tglx@linutronix.de, keescook@chromium.org Reply-To: mingo@kernel.org, peterz@infradead.org, hpa@zytor.com, brgerst@gmail.com, ast@plumgrid.com, luto@amacapital.net, fweisbec@gmail.com, torvalds@linux-foundation.org, bp@alien8.de, linux-kernel@vger.kernel.org, dvlasenk@redhat.com, rostedt@goodmis.org, oleg@redhat.com, tglx@linutronix.de, wad@chromium.org, keescook@chromium.org In-Reply-To: <1431722346-26585-1-git-send-email-dvlasenk@redhat.com> References: <1431722346-26585-1-git-send-email-dvlasenk@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/apic] x86/asm/entry/64: Use shorter MOVs from segment registers Git-Commit-ID: adeb5537849d9db428fe0ddc3562e5a765a347e2 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: adeb5537849d9db428fe0ddc3562e5a765a347e2 Gitweb: http://git.kernel.org/tip/adeb5537849d9db428fe0ddc3562e5a765a347e2 Author: Denys Vlasenko AuthorDate: Fri, 15 May 2015 22:39:06 +0200 Committer: Ingo Molnar CommitDate: Sun, 17 May 2015 07:57:54 +0200 x86/asm/entry/64: Use shorter MOVs from segment registers The "movw %ds,%cx" instruction needs a 0x66 prefix, while "movl %ds,%ecx" does not. The difference is that latter form (on 64-bit CPUs) overwrites the entire %ecx, not only its lower half. But subsequent code doesn't depend on the value of upper half of %ecx, so we can safely use the shorter instruction. The new code is also faster than the old one - now we don't depend on the old value of %ecx, but this code fragment is not performance-critical so it does not matter much. Signed-off-by: Denys Vlasenko Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Will Drewry Link: http://lkml.kernel.org/r/1431722346-26585-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 09c3f9e..47b9581 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1190,17 +1190,17 @@ ENTRY(xen_failsafe_callback) /*CFI_REL_OFFSET ds,DS*/ CFI_REL_OFFSET r11,8 CFI_REL_OFFSET rcx,0 - movw %ds,%cx + movl %ds,%ecx cmpw %cx,0x10(%rsp) CFI_REMEMBER_STATE jne 1f - movw %es,%cx + movl %es,%ecx cmpw %cx,0x18(%rsp) jne 1f - movw %fs,%cx + movl %fs,%ecx cmpw %cx,0x20(%rsp) jne 1f - movw %gs,%cx + movl %gs,%ecx cmpw %cx,0x28(%rsp) jne 1f /* All segments match their saved values => Category 2 (Bad IRET). */