From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BCD00CA9EA1 for ; Fri, 18 Oct 2019 09:49:37 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9107C222BD for ; Fri, 18 Oct 2019 09:49:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9107C222BD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37240 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLOt6-0008Gc-B8 for qemu-devel@archiver.kernel.org; Fri, 18 Oct 2019 05:49:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49154) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLOre-0006he-HT for qemu-devel@nongnu.org; Fri, 18 Oct 2019 05:48:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iLOrd-0005ZC-IS for qemu-devel@nongnu.org; Fri, 18 Oct 2019 05:48:06 -0400 Received: from relay.sw.ru ([185.231.240.75]:42964) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iLOra-0005Wb-Ul; Fri, 18 Oct 2019 05:48:03 -0400 Received: from [10.94.3.0] (helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92.2) (envelope-from ) id 1iLOrY-0004Ah-2M; Fri, 18 Oct 2019 12:48:00 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Subject: [PATCH v8 2/3] docs: define padding for qcow2 header Date: Fri, 18 Oct 2019 12:47:57 +0300 Message-Id: <20191018094758.7124-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20191018094758.7124-1-vsementsov@virtuozzo.com> References: <20191018094758.7124-1-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 185.231.240.75 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, armbru@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, dplotnikov@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Header extensions ends are already defined to be multiply of 8. Let's gently ask for header length to be a multiply of 8 too, when we have some additional fields. Requiring this may be considered as an incompatible change, so the padding is optional. Actually, padding is allowed before this patch (due to definition of additional fields), the only actual change is "SHOULD" word. Signed-off-by: Vladimir Sementsov-Ogievskiy --- docs/interop/qcow2.txt | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index 4709f3bb30..b971e59b1a 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -185,6 +185,11 @@ which is covered by @header_length must be zeroed. < ... No additional fields in the header currently ... > +Header padding + If @header_length is larger than 104, software SHOULD make it a + multiply of 8, adding zero-padding after additional fields. Still the + padding is optional and may be absent in the image. + Directly after the image header, optional sections called header extensions can be stored. Each extension has a structure like the following: -- 2.21.0