Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754542Ab0LHJSO (ORCPT ); Wed, 8 Dec 2010 04:18:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30563 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752918Ab0LHJSM (ORCPT ); Wed, 8 Dec 2010 04:18:12 -0500 Message-ID: <4CFF4D4C.2070002@redhat.com> Date: Wed, 08 Dec 2010 11:18:04 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101103 Fedora/1.0-0.33.b2pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.6 MIME-Version: 1.0 To: David Sharp CC: rostedt@goodmis.org, linux-kernel@vger.kernel.org, mrubin@google.com, kvm-devel Subject: Re: [PATCH 07/15] ftrace: fix event alignment: kvm:kvm_hv_hypercall References: <1291421609-14665-1-git-send-email-dhsharp@google.com> <1291421609-14665-8-git-send-email-dhsharp@google.com> <4CF9F7AB.8050802@redhat.com> <4CFDFCEF.3080708@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1246 Lines: 30 On 12/07/2010 11:16 PM, David Sharp wrote: > > > > I don't understand this. Can you elaborate? What does "32-bit addressable" > > mean? > > The ring buffer gives you space that is a multiple of 4 bytes in > length, and 32-bit aligned. Therefore it is useless to attempt to > align the structure beyond 32-bit boundaries, eg, a 64-bit boundary, > because it is unpredictable if the memory the structure will be > written to is at a 64-bit boundary (addr % 8 could be 0 or 4). > > > And "predicated on packing the event structures"? Is the structure > > __attribute__((packed)), or is it not? > > It is not packed in Linus' tree, but one of the patches before this > patch in this patch series adds __attribute__((packed)). This patch > assumes that the event packing patch has been applied. This patch > should not be applied if the packing patch is not (hence, > "predicated"). Thanks for the explanations, it makes sense now. -- error compiling committee.c: too many arguments to function -- 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/