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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 0C31EC001E0 for ; Mon, 23 Oct 2023 09:43:37 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qurT1-0001wg-EG; Mon, 23 Oct 2023 05:43:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qurSy-0001wA-SX; Mon, 23 Oct 2023 05:43:21 -0400 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qurSv-0006ub-LQ; Mon, 23 Oct 2023 05:43:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: MIME-Version:Message-ID:References:In-Reply-To:Subject:CC:To:From:Date:Sender :Reply-To:Content-ID:Content-Description; bh=QJnLNJLIKQ/1yQL84M0rKohbw6CIp8aEbajAdE1XPdk=; b=CUdLWyALBJqmFbDGesKzP61pFX yMyqMvl8eVP0caNQqIuXFssX8lBUzWgpK0Cz1fE8ycmQ7Zc364gqWYFOTEzYFjujFruaRGkPf/g16 2GvuZQFH7+oO5B5p06BuB9jm6y2Zb0P3hOi7BsVk8I5q9ZzHdu8NlWI5fNR9PAEQX1FoAvUwcQygR BrsvhK9U4XPB2XlRKtxIRyatSt0Ur8ot4pBTYRH2JCADNdaRtv6ro02JzxVUyyL4XCxYYdUYirxQk sSvo6tPiHXwM1MjlSxzPFY4mccQVObrvA0FIliR8oJ5LExfja1ipELp+yx7XX+ndJ15ku4AvAk9s8 aSwfOOyQ==; Received: from [31.94.4.150] (helo=[IPv6:::1]) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qurSo-00D2s3-IS; Mon, 23 Oct 2023 09:43:10 +0000 Date: Mon, 23 Oct 2023 10:42:58 +0100 From: David Woodhouse To: Igor Mammedov CC: qemu-devel@nongnu.org, Kevin Wolf , Hanna Reitz , Stefano Stabellini , Anthony Perard , Paul Durrant , =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= , Paolo Bonzini , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , Marcelo Tosatti , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, =?ISO-8859-1?Q?Daniel_P=2E_Berrang=E9?= Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_11/12=5D_hw/xen=3A_automaticall?= =?US-ASCII?Q?y_assign_device_index_to_block_devices?= User-Agent: K-9 Mail for Android In-Reply-To: <20231023113002.0e83c209@imammedo.users.ipa.redhat.com> References: <20231016151909.22133-1-dwmw2@infradead.org> <20231016151909.22133-12-dwmw2@infradead.org> <20231018093239.3d525fd8@imammedo.users.ipa.redhat.com> <3f3487af227dcdce7afb37e8406d5ce8dcdbf55f.camel@infradead.org> <20231023113002.0e83c209@imammedo.users.ipa.redhat.com> Message-ID: <8CBFDABE-6BD7-4924-BB69-EF5EAA04A34D@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+91fa634947ba19782c4e+7365+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 23 October 2023 10:30:02 BST, Igor Mammedov wro= te: >On Wed, 18 Oct 2023 09:32:47 +0100 >David Woodhouse wrote: > >> On Wed, 2023-10-18 at 09:32 +0200, Igor Mammedov wrote: >> > On Mon, 16 Oct 2023 16:19:08 +0100 >> > David Woodhouse wrote: >> > =20 >> > > From: David Woodhouse >> > > =20 >> >=20 >> > is this index a user (guest) visible? =20 >>=20 >> Yes=2E It defines what block device (e=2Eg=2E /dev/xvda) the disk appea= rs as >> in the guest=2E In the common case, it literally encodes the Linux >> major/minor numbers=2E So xvda (major 202) is 0xca00, xvdb is 0xca10 et= c=2E > >that makes 'index' an implicit ABI and a subject to versioning >when the way it's assigned changes (i=2Ee=2E one has to use versioned >machine types to keep older versions working the they used to)=2E > >>From what I remember it's discouraged to make QEMU invent >various IDs that are part of ABI (guest or mgmt side)=2E >Instead it's preferred for mgmt side/user to provide that explicitly=2E > >Basically you are trading off manageability/simplicity at QEMU >level with CLI usability for human user=2E >I don't care much as long as it is hidden within xen code base, >but maybe libvirt does=2E Well, it can still be set explicitly=2E So not so much a "trade-off" as ad= ding the option for the user to choose the simple way=2E Yes, in a way it's an ABI, just like the dynamic assignment of PCI devfn f= or network devices added with "-nic"=2E And I think also for virtio block d= evices too? And for the ISA ne2000=2E But it seems unlikely that we'll ever really want to change "the first one= is xvda, the second is xvdb=2E=2E=2E=2E" From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1qurT1-0001wf-9b for mharc-qemu-devel@gnu.org; Mon, 23 Oct 2023 05:43:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qurSy-0001wA-SX; Mon, 23 Oct 2023 05:43:21 -0400 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qurSv-0006ub-LQ; Mon, 23 Oct 2023 05:43:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: MIME-Version:Message-ID:References:In-Reply-To:Subject:CC:To:From:Date:Sender :Reply-To:Content-ID:Content-Description; bh=QJnLNJLIKQ/1yQL84M0rKohbw6CIp8aEbajAdE1XPdk=; b=CUdLWyALBJqmFbDGesKzP61pFX yMyqMvl8eVP0caNQqIuXFssX8lBUzWgpK0Cz1fE8ycmQ7Zc364gqWYFOTEzYFjujFruaRGkPf/g16 2GvuZQFH7+oO5B5p06BuB9jm6y2Zb0P3hOi7BsVk8I5q9ZzHdu8NlWI5fNR9PAEQX1FoAvUwcQygR BrsvhK9U4XPB2XlRKtxIRyatSt0Ur8ot4pBTYRH2JCADNdaRtv6ro02JzxVUyyL4XCxYYdUYirxQk sSvo6tPiHXwM1MjlSxzPFY4mccQVObrvA0FIliR8oJ5LExfja1ipELp+yx7XX+ndJ15ku4AvAk9s8 aSwfOOyQ==; Received: from [31.94.4.150] (helo=[IPv6:::1]) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qurSo-00D2s3-IS; Mon, 23 Oct 2023 09:43:10 +0000 Date: Mon, 23 Oct 2023 10:42:58 +0100 From: David Woodhouse To: Igor Mammedov CC: qemu-devel@nongnu.org, Kevin Wolf , Hanna Reitz , Stefano Stabellini , Anthony Perard , Paul Durrant , =?ISO-8859-1?Q?Marc-Andr=E9_Lureau?= , Paolo Bonzini , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , Marcelo Tosatti , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, =?ISO-8859-1?Q?Daniel_P=2E_Berrang=E9?= Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_11/12=5D_hw/xen=3A_automaticall?= =?US-ASCII?Q?y_assign_device_index_to_block_devices?= User-Agent: K-9 Mail for Android In-Reply-To: <20231023113002.0e83c209@imammedo.users.ipa.redhat.com> References: <20231016151909.22133-1-dwmw2@infradead.org> <20231016151909.22133-12-dwmw2@infradead.org> <20231018093239.3d525fd8@imammedo.users.ipa.redhat.com> <3f3487af227dcdce7afb37e8406d5ce8dcdbf55f.camel@infradead.org> <20231023113002.0e83c209@imammedo.users.ipa.redhat.com> Message-ID: <8CBFDABE-6BD7-4924-BB69-EF5EAA04A34D@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1236::1; envelope-from=BATV+91fa634947ba19782c4e+7365+infradead.org+dwmw2@casper.srs.infradead.org; helo=casper.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 Oct 2023 09:43:21 -0000 Message-ID: <20231023094258.TKxymuOj67euIv-chxxMet8HIBRXDuiEcntixAchacQ@z> On 23 October 2023 10:30:02 BST, Igor Mammedov wro= te: >On Wed, 18 Oct 2023 09:32:47 +0100 >David Woodhouse wrote: > >> On Wed, 2023-10-18 at 09:32 +0200, Igor Mammedov wrote: >> > On Mon, 16 Oct 2023 16:19:08 +0100 >> > David Woodhouse wrote: >> > =20 >> > > From: David Woodhouse >> > > =20 >> >=20 >> > is this index a user (guest) visible? =20 >>=20 >> Yes=2E It defines what block device (e=2Eg=2E /dev/xvda) the disk appea= rs as >> in the guest=2E In the common case, it literally encodes the Linux >> major/minor numbers=2E So xvda (major 202) is 0xca00, xvdb is 0xca10 et= c=2E > >that makes 'index' an implicit ABI and a subject to versioning >when the way it's assigned changes (i=2Ee=2E one has to use versioned >machine types to keep older versions working the they used to)=2E > >From what I remember it's discouraged to make QEMU invent >various IDs that are part of ABI (guest or mgmt side)=2E >Instead it's preferred for mgmt side/user to provide that explicitly=2E > >Basically you are trading off manageability/simplicity at QEMU >level with CLI usability for human user=2E >I don't care much as long as it is hidden within xen code base, >but maybe libvirt does=2E Well, it can still be set explicitly=2E So not so much a "trade-off" as ad= ding the option for the user to choose the simple way=2E Yes, in a way it's an ABI, just like the dynamic assignment of PCI devfn f= or network devices added with "-nic"=2E And I think also for virtio block d= evices too? And for the ISA ne2000=2E But it seems unlikely that we'll ever really want to change "the first one= is xvda, the second is xvdb=2E=2E=2E=2E"