Received: by 2002:a05:6a10:a0d1:0:0:0:0 with SMTP id j17csp836341pxa; Sat, 22 Aug 2020 01:43:53 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzBSZb4Zj5ZCHELbrwbw7cuwCfChCeeCPYGvq6fnsJrMPB+8yCOOTts89ffD6L2eCmD2bby X-Received: by 2002:a50:b946:: with SMTP id m64mr6645088ede.92.1598085833191; Sat, 22 Aug 2020 01:43:53 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1598085833; cv=none; d=google.com; s=arc-20160816; b=yZ+pj41SgDJN2SAyg57whPZBl0joRAXfY0XKbULHlJiZC9e8h7ee4XJCig9zqym/yV xDhyKk0AyqKYvo/VymxaaJM4f9yNDdTjBi7uJrRdnNn5MkxlV76couO9/F/9hYbULVEZ wFSlMRJxb7xpOmiry92bEb/91xoA9epB9xQH5XCKUlH6e6/b03xOFCWG2LR9yu08V8MD GvqWrm+R7dUd47FdTBf6eYo9W4zKtrPpp6MkqzOTeTgj7KhbFPOvjM7E9dy5KpjvSz6B 7PPe9pfiWQReNkyMg1Iiw88lOsrncr9Q5Mn2uJX0gZTTKdk3H6VOKjVsJa8MfPCIHYAv 7rYQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:in-reply-to :content-disposition:mime-version:references:message-id:subject:cc :to:from:date; bh=l2rS6KdH1mqz1o0PDH6npT7GbCr3VoiGm91IrwrfVXg=; b=Uq4GJb81zaQ0WVIF4T5/L0G6Yb1BbfEJfLQXeln0m1h+6+RsqAHZCVnVNtxUwZqMqD czbLiMbPAqbb1d7u0pK48dqqr1nCX53opcDG0Ikw5XxDICjH8yhy1iF5WrHR/WQbdvry IgnMvQQX8SIOmPWOh+zWE6kjhKMXAEFSHDJAGJxoaMKGqFVhdbMpRtcHdM9YlqyKs34U TpcKof2ETPm1+JivIwwmnrpfZQ47tugFcT1bLDS0m0JwywgdF22mbYdACZp5OXOCH59Y z75M8eTmdxNryan+bf8Hzy6w4GSmWS+8ThaVyIbALdDqDHqvTJggvGGuGYPU1x8tBg6S Az4w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id z12si2837718edp.120.2020.08.22.01.43.29; Sat, 22 Aug 2020 01:43:53 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726169AbgHVInC (ORCPT + 99 others); Sat, 22 Aug 2020 04:43:02 -0400 Received: from gate.crashing.org ([63.228.1.57]:50298 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725877AbgHVInC (ORCPT ); Sat, 22 Aug 2020 04:43:02 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 07M8fc2M011586; Sat, 22 Aug 2020 03:41:38 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 07M8fX7Z011585; Sat, 22 Aug 2020 03:41:33 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Sat, 22 Aug 2020 03:41:33 -0500 From: Segher Boessenkool To: Arvind Sankar Cc: Thomas Gleixner , Nick Desaulniers , "Paul E. McKenney" , Ingo Molnar , Arnd Bergmann , Borislav Petkov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , "Kirill A. Shutemov" , Zhenzhong Duan , Kees Cook , Peter Zijlstra , Juergen Gross , Andy Lutomirski , Andrew Cooper , LKML , clang-built-linux , Will Deacon , Linus Torvalds Subject: Re: [PATCH] x86: work around clang IAS bug referencing __force_order Message-ID: <20200822084133.GL28786@gate.crashing.org> References: <87h7t6tpye.fsf@nanos.tec.linutronix.de> <20200813173701.GC4295@paulmck-ThinkPad-P72> <20200813180933.GA532283@rani.riverdale.lan> <875z9dioll.fsf@nanos.tec.linutronix.de> <20200820130641.GA536306@rani.riverdale.lan> <87zh6ohm03.fsf@nanos.tec.linutronix.de> <20200821230435.GA56974@rani.riverdale.lan> <87eenzqzmr.fsf@nanos.tec.linutronix.de> <20200822035552.GA104886@rani.riverdale.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200822035552.GA104886@rani.riverdale.lan> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arvind, On Fri, Aug 21, 2020 at 11:55:52PM -0400, Arvind Sankar wrote: > Cc Segher. > > Segher, we were looking at gcc PR82602, where IRA could reorder volatile > asm's (reported on ARM). The fix was backported to gcc-6. I know ;-) > Do you know if > there is any reason the problem couldn't occur on x86 on older gcc > without the fix? No, I see no particular reason, at least GCC 5 seems vulnerable. (The GCC 5 release branch was closed at the time this bug report was made, already). There is no reason I see why it would work on x86 but fail elsewhere, either. Segher