From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48293) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cHRNd-0002My-KH for qemu-devel@nongnu.org; Thu, 15 Dec 2016 03:27:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cHRNY-0008LH-M2 for qemu-devel@nongnu.org; Thu, 15 Dec 2016 03:27:09 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50472 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cHRNY-0008L1-GH for qemu-devel@nongnu.org; Thu, 15 Dec 2016 03:27:04 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uBF8Nuj9040040 for ; Thu, 15 Dec 2016 03:27:03 -0500 Received: from e06smtp08.uk.ibm.com (e06smtp08.uk.ibm.com [195.75.94.104]) by mx0a-001b2d01.pphosted.com with ESMTP id 27bnute700-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 15 Dec 2016 03:27:03 -0500 Received: from localhost by e06smtp08.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 15 Dec 2016 08:27:01 -0000 Date: Thu, 15 Dec 2016 09:26:56 +0100 From: Cornelia Huck In-Reply-To: <20161215073808.GB26169@stefanha-x1.localdomain> References: <20161214163035.3297-1-maxime.coquelin@redhat.com> <20161215073808.GB26169@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20161215092656.2e1244c0.cornelia.huck@de.ibm.com> Subject: Re: [Qemu-devel] [PATCH v3] virtio-pci: Fix cross-version migration with older machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Maxime Coquelin , mdroth@linux.vnet.ibm.com, stefanha@redhat.com, qemu-devel@nongnu.org, mst@redhat.com, marcel@redhat.com, "Dr . David Alan Gilbert" On Thu, 15 Dec 2016 07:38:09 +0000 Stefan Hajnoczi wrote: > On Wed, Dec 14, 2016 at 05:30:35PM +0100, Maxime Coquelin wrote: > > This patch fixes a cross-version migration regression introduced > > by commit d1b4259f ("virtio-bus: Plug devices after features are > > negotiated"). > > > > The problem is encountered when host's vhost backend does not support > > VIRTIO_F_VERSION_1, and migration is initiated from a v2.7 or prior > > machine with virtio-pci modern capabilities enabled to a v2.8 machine. > > > > In this case, modern capabilities get exposed to the guest by the source, > > whereas the target will detect version 1 is not supported so will only > > expose legacy capabilities. > > > > The problem is fixed by introducing a new "x-ignore-backend-features" > > property, which is set in v2.7 and prior compatibility modes. Doing this, > > v2.7 machine keeps its broken behaviour (enabling modern while version > > is not supported), and newer machines will behave correctly. > > > > Reported-by: Michael Roth > > Suggested-by: Stefan Hajnoczi > > Cc: Michael S. Tsirkin > > Cc: Cornelia Huck > > Cc: Dr. David Alan Gilbert > > Reviewed-by: Marcel Apfelbaum > > Reviewed-by: Stefan Hajnoczi > > Tested-by: Michael Roth > > Signed-off-by: Maxime Coquelin > > --- > > > > V3 fixes commit message with the new property name. > > V2 changes the naming as proposed by Michael T.and Cornelia, and > > fixes commit message. > > > > hw/virtio/virtio-pci.c | 5 ++++- > > hw/virtio/virtio-pci.h | 1 + > > include/hw/compat.h | 4 ++++ > > 3 files changed, 9 insertions(+), 1 deletion(-) > > Thanks, applied to my staging tree: > https://github.com/stefanha/qemu/commits/staging > > Stefan Hm, missing my R-b I gave for v2... feel free to add Reviewed-by: Cornelia Huck if you still want to change it.