From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60963) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a4B4J-0003Qb-DU for qemu-devel@nongnu.org; Wed, 02 Dec 2015 12:19:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a4B4F-0001qu-Ou for qemu-devel@nongnu.org; Wed, 02 Dec 2015 12:19:51 -0500 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:42003) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a4B4F-0001qh-FS for qemu-devel@nongnu.org; Wed, 02 Dec 2015 12:19:47 -0500 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 2 Dec 2015 17:19:45 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id B06A0219005C for ; Wed, 2 Dec 2015 17:19:37 +0000 (GMT) Received: from d06av08.portsmouth.uk.ibm.com (d06av08.portsmouth.uk.ibm.com [9.149.37.249]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id tB2HJi2B6357480 for ; Wed, 2 Dec 2015 17:19:44 GMT Received: from d06av08.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av08.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id tB2HJhlO003193 for ; Wed, 2 Dec 2015 10:19:44 -0700 Date: Wed, 2 Dec 2015 18:19:42 +0100 From: Cornelia Huck Message-ID: <20151202181942.1a9497c2.cornelia.huck@de.ibm.com> In-Reply-To: <20151202184036-mutt-send-email-mst@redhat.com> References: <1449065398-45267-1-git-send-email-cornelia.huck@de.ibm.com> <20151202184036-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH for-2.5] virtio: handle non-virtio-1-capable backend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: borntraeger@de.ibm.com, jasowang@redhat.com, qemu-devel@nongnu.org On Wed, 2 Dec 2015 18:43:05 +0200 "Michael S. Tsirkin" wrote: > On Wed, Dec 02, 2015 at 03:09:58PM +0100, Cornelia Huck wrote: > > If you run a qemu advertising VERSION_1 with an old kernel where > > vhost did not yet support VERSION_1, you'll end up with a device > > that is {modern pci|ccw revision 1} but does not advertise VERSION_1. > > This is not a sensible configuration and is rejected by the Linux > > guest drivers. > > > > To fix this, add a ->post_plugged() callback invoked after features > > have been queried that can handle the VERSION_1 bit being withdrawn > > and change pci (only setup modern if VERSION_1 is still present) and > > ccw (fall back to revision 0 if VERSION_1 is gone). > > > > Signed-off-by: Cornelia Huck > > > Unfortunately this is too late: we need to know > whether modern will be supported to know whether > to add the pci express capability :( > > Maybe this should be moved into plugged > callback? As discussed on irc: I'll cut this down to ccw only for 2.5, and we'll rethink for 2.6. Patch in progress.