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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27F29C001E0 for ; Mon, 23 Oct 2023 13:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230044AbjJWNqw (ORCPT ); Mon, 23 Oct 2023 09:46:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbjJWNqu (ORCPT ); Mon, 23 Oct 2023 09:46:50 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A636E4 for ; Mon, 23 Oct 2023 06:46:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698068759; 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: in-reply-to:in-reply-to:references:references; bh=PRwDvjlRKO8xrlwJvcJXG0QiFBX/VuVy6rRUymKs+DU=; b=LEzQPwiNkc1yz9w0HNvBEwxU6PndrGS8P0kRkjiXAKLO8fZuhOBcoNgPJcwXs6NNUfnImb ld6GgJFU6YvG8pR9GkcZjY1JUfiN930wvOGDi5SVJWU3w5m7sAcGOKl184oYYcgu2w8K3B msQFWkd/KRpNsvChNWrz/DM0oguawas= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-263-mjSKRdUpPyGnGYhKh02Sbg-1; Mon, 23 Oct 2023 09:45:55 -0400 X-MC-Unique: mjSKRdUpPyGnGYhKh02Sbg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1F555101AA75; Mon, 23 Oct 2023 13:45:55 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.144]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6EBF01C060B6; Mon, 23 Oct 2023 13:45:52 +0000 (UTC) Date: Mon, 23 Oct 2023 15:45:51 +0200 From: Kevin Wolf To: Igor Mammedov Cc: David Woodhouse , qemu-devel@nongnu.org, 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, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH 11/12] hw/xen: automatically assign device index to block devices Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231023113002.0e83c209@imammedo.users.ipa.redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Am 23.10.2023 um 11:30 hat Igor Mammedov geschrieben: > 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: > > > > > > > From: David Woodhouse > > > > > > > > > > is this index a user (guest) visible? > > > > Yes. It defines what block device (e.g. /dev/xvda) the disk appears as > > in the guest. In the common case, it literally encodes the Linux > > major/minor numbers. So xvda (major 202) is 0xca00, xvdb is 0xca10 etc. > > that makes 'index' an implicit ABI and a subject to versioning > when the way it's assigned changes (i.e. one has to use versioned > machine types to keep older versions working the they used to). > > From what I remember it's discouraged to make QEMU invent > various IDs that are part of ABI (guest or mgmt side). > Instead it's preferred for mgmt side/user to provide that explicitly. > > Basically you are trading off manageability/simplicity at QEMU > level with CLI usability for human user. > I don't care much as long as it is hidden within xen code base, > but maybe libvirt does. -drive is mostly a convenience option for human users anyway. Management tools should use a combination of -blockdev and -device. Kevin