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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2B39CC2BA19 for ; Mon, 6 Apr 2020 13:33:35 +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 E90F02332A for ; Mon, 6 Apr 2020 13:33:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AE/Q8wP7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E90F02332A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:60218 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jLRsc-0005LP-4S for qemu-devel@archiver.kernel.org; Mon, 06 Apr 2020 09:33:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50328) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jLRrc-0004Z2-Pz for qemu-devel@nongnu.org; Mon, 06 Apr 2020 09:32:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jLRrb-0007YL-1Z for qemu-devel@nongnu.org; Mon, 06 Apr 2020 09:32:32 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:50044 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jLRra-0007XJ-TG for qemu-devel@nongnu.org; Mon, 06 Apr 2020 09:32:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1586179949; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=166AdI31MoDy3Jd//uwsQZX7dQM1UTS5BT1+m1oTWBQ=; b=AE/Q8wP7KY25CKDso4vs7juj5drCvB+bRLHDrJuaDwWjfYVOR+y/+T7qJE7D8QiaZ5fWQn DqvZi76icykw5IqvvIBMOy+Zki2YxKA2Y2Vc/DWEiSXpv/TIoi09OTjxdhCMmNMcGKN0xi 6Ca1tkNdCTDkn+Cwhp5gwSHacTSm0+E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-65-JxtHP2nTOUuhEKz6tOsaCA-1; Mon, 06 Apr 2020 09:32:25 -0400 X-MC-Unique: JxtHP2nTOUuhEKz6tOsaCA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9AEE61084431; Mon, 6 Apr 2020 13:32:24 +0000 (UTC) Received: from [10.3.114.49] (ovpn-114-49.phx2.redhat.com [10.3.114.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 42D9760C87; Mon, 6 Apr 2020 13:32:23 +0000 (UTC) Subject: Re: [PATCH for-5.0? v2] qcow2: Explicit mention of padding bytes To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org References: <20200403181907.878751-1-eblake@redhat.com> <8fe869d5-baf5-6d04-78d4-bee89cd7ef47@virtuozzo.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <3f720e97-a499-67f9-f85c-1dba29ec9551@redhat.com> Date: Mon, 6 Apr 2020 08:32:22 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <8fe869d5-baf5-6d04-78d4-bee89cd7ef47@virtuozzo.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: Kevin Wolf , "open list:qcow2" , mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/6/20 3:50 AM, Vladimir Sementsov-Ogievskiy wrote: > 03.04.2020 21:19, Eric Blake wrote: >> Although we already covered the need for padding bytes with our >> changes in commit 3ae3fcfa, commit 66fcbca5 just added one byte and >> relied on the rest of the text for implicitly covering 7 padding >> bytes.=C2=A0 For consistency with other parts of the header (such as the >> header extension format listing padding from n - m, or the snapshot >> table entry mentioning variable padding), we might as well call out >> the remaining 7 bytes as padding until such time (as any) as they gain >> another meaning. >> >> Signed-off-by: Eric Blake >> --- >> >> v2: Call out explicit byte range rather than '105 - m' [Max] >> >> Safe for 5.0 as it is just a doc fix, but only if we actually want it. >> >> =C2=A0 docs/interop/qcow2.txt | 1 + >> =C2=A0 1 file changed, 1 insertion(+) >> >> diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt >> index 640e0eca4000..80728bc2008d 100644 >> --- a/docs/interop/qcow2.txt >> +++ b/docs/interop/qcow2.txt >> @@ -210,3 +210,4 @@ version 2. >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Available compressio= n type values: >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 0: zlib >> >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 105 - 111:=C2=A0 Padding, le= ave as zero. >> >=20 > Looking on this in separate, I'd make a software which will zero this=20 > padding unconditionally. However, if it's an existing image which we=20 > just open, we should keep the content we read.. On the other hand, of=20 > course, if read the whole spec, everything is clear. Maybe: 105 - 111: Padding, contents defined below rather than an explicit mention of setting to 0? --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org