From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53214) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cHTos-0004a4-CZ for qemu-devel@nongnu.org; Thu, 15 Dec 2016 06:03:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cHToo-0003Ie-FX for qemu-devel@nongnu.org; Thu, 15 Dec 2016 06:03:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37646) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cHToo-0003Gm-8Q for qemu-devel@nongnu.org; Thu, 15 Dec 2016 06:03:22 -0500 References: <20161214163035.3297-1-maxime.coquelin@redhat.com> <20161215073808.GB26169@stefanha-x1.localdomain> <20161215092656.2e1244c0.cornelia.huck@de.ibm.com> <20161215103145.GG2762@stefanha-x1.localdomain> From: Maxime Coquelin Message-ID: <185aa91e-b50d-c068-0b1c-6b5c1371393d@redhat.com> Date: Thu, 15 Dec 2016 12:03:15 +0100 MIME-Version: 1.0 In-Reply-To: <20161215103145.GG2762@stefanha-x1.localdomain> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit 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 , Cornelia Huck Cc: Stefan Hajnoczi , mdroth@linux.vnet.ibm.com, qemu-devel@nongnu.org, mst@redhat.com, marcel@redhat.com, "Dr . David Alan Gilbert" On 12/15/2016 11:31 AM, Stefan Hajnoczi wrote: > On Thu, Dec 15, 2016 at 09:26:56AM +0100, Cornelia Huck wrote: >> 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. > > Sorry, the R-b didn't make it into v2.8.0-rc4. > > The patch management scripts I use apply all R-b for a single email > thread. They do not look at previous revisions (it would be hard to > tell which R-b still stand and which do not). The usual solution is for > the patch author to include previous R-b in new revisions as long as > code changes aren't substantial. Right that's my fault, sorry Cornelia. Maxime > > Stefan >