From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753266Ab1HIW1x (ORCPT ); Tue, 9 Aug 2011 18:27:53 -0400 Received: from mga03.intel.com ([143.182.124.21]:50048 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752878Ab1HIW1w (ORCPT ); Tue, 9 Aug 2011 18:27:52 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,345,1309762800"; d="scan'208";a="5600653" Subject: Re: New vsyscall emulation breaks JITs From: Suresh Siddha Reply-To: Suresh Siddha To: "H. Peter Anvin" Cc: Andrew Lutomirski , Andi Kleen , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "torvalds@linux-foundation.org" , "lueckintel@yahoo.com" , "kimwooyoung@gmail.com" In-Reply-To: <4E3C8B8A.3080007@zytor.com> References: <20110805200945.GA14014@tassilo.jf.intel.com> <4E3C5154.2050307@zytor.com> <4E3C571C.1070903@zytor.com> <20110805205222.GK5782@one.firstfloor.org> <20110805212153.GL5782@one.firstfloor.org> <4E3C6982.5050901@zytor.com> <4E3C8B8A.3080007@zytor.com> Content-Type: text/plain Organization: Intel Corp Date: Tue, 09 Aug 2011 15:27:24 -0700 Message-Id: <1312928844.25213.25.camel@sbsiddha-MOBL3.sc.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-08-05 at 17:32 -0700, H. Peter Anvin wrote: > On 08/05/2011 05:20 PM, Andrew Lutomirski wrote: > > > > I was thinking of 0x20 - 0x39. 0x40, 0x41, and 0x42 should do the > > trick. I'll cook up a patch. > > > > If you want to keep those vectors available for devices as well, we > > could hook do_general_protection instead, but that's a little messy. > > Are there x86 machines out there that are starved for interrupt > > vectors? > > > > Yes, but 3 aren't going to matter much. > > However, on systems which have interrupt migration enabled we're not > using 0x21-0x2f for anything (because we need a single interrupt with > absolutely lowest priority). Double checked to make sure and we actually allow 0x21-0x2f to be used for device interrupts (commit 6579b474572fd54c583ac074e8e7aaae926c62ef). So reserving the vectors in this range should be same as reserving in any other range available for use. Thanks. > Out of that range, there are a couple of > values which should be safe to use because they would be harmless > instructions of various forms: > > 0x24 - AND AL, imm8 > 0x25 - AND EAX, imm32 > 0x26 - ES: > 0x2C - SUB AL, imm8 > 0x2D - SUB EAX, imm32 > 0x2E - CS: > > [Cc: Suresh who is the expert on the interrupt assignments] > > -hpa