Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753101Ab3GNT3H (ORCPT ); Sun, 14 Jul 2013 15:29:07 -0400 Received: from mail-vc0-f181.google.com ([209.85.220.181]:58056 "EHLO mail-vc0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752460Ab3GNT3G (ORCPT ); Sun, 14 Jul 2013 15:29:06 -0400 MIME-Version: 1.0 In-Reply-To: <51E2FACA.3050801@goop.org> References: <1373806562-30422-1-git-send-email-artagnon@gmail.com> <51E2FACA.3050801@goop.org> Date: Sun, 14 Jul 2013 12:29:04 -0700 X-Google-Sender-Auth: f8DlpoWZ7c_isD1tQJiAKu2WroI Message-ID: Subject: Re: [PATCH] x86/asm: avoid mnemonics without type suffix From: Linus Torvalds To: Jeremy Fitzhardinge Cc: Ramkumar Ramachandra , LKML , Andi Kleen , Ingo Molnar , Thomas Gleixner , Eli Friedman , Jim Grosbach , Stephen Checkoway , LLVMdev Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1225 Lines: 27 On Sun, Jul 14, 2013 at 12:23 PM, Jeremy Fitzhardinge wrote: > > It looks like that if the base address isn't aligned then neither is the > generated access, so you could get a protection fault if it overlaps a > page boundary, which is a semantic rather than purely operational > difference. You could also get AC fault for the btq if the thing is only long-aligned. But yes, I checked the Intel manuals too, and the access size is actually not well-specified (even the 16-bit case says "may", I think), so both the page-fault and the alignment fault are purely theoretical. And i'm too lazy to bother trying the (easily testable) alignment fault case in practice, since (a) nobody cares and (b) nobody cares. In the (unlikely) situation that somebody actually cares, that somebody should obviously then have to specify "btl" vs "btq". Assuming the hardware cares, which is testable but might be micro-architecture dependent. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/