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Violators will be prosecuted for from ; Wed, 14 Dec 2016 09:02:27 -0700 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Michael Roth In-Reply-To: <20161214171501-mutt-send-email-mst@kernel.org> References: <20161214125237.20850-1-maxime.coquelin@redhat.com> <20161214150852.5009.51009@loki> <20161214171501-mutt-send-email-mst@kernel.org> Date: Wed, 14 Dec 2016 10:02:15 -0600 Message-Id: <20161214160215.5009.32685@loki> Subject: Re: [Qemu-devel] [PATCH] virtio-pci: Fix cross-version migration with older machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Maxime Coquelin , stefanha@redhat.com, qemu-devel@nongnu.org, cornelia.huck@de.ibm.com, marcel@redhat.com, "Dr . David Alan Gilbert" Quoting Michael S. Tsirkin (2016-12-14 09:15:38) > On Wed, Dec 14, 2016 at 09:08:52AM -0600, Michael Roth wrote: > > Quoting Maxime Coquelin (2016-12-14 06:52:37) > > > 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 sou= rce, > > > 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-modern-broken" 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: Marcel Apfelbaum > > > Cc: Dr. David Alan Gilbert > > > Signed-off-by: Maxime Coquelin > > = > > Tested-by: Michael Roth > > = > > I can confirm this fixes the original issue I reported. I also did a > > number of sanity runs with 2.7/2.8/pc-i440fx-2.{6,7,8} using various > > combinations of disable-modern=3Dtrue/false on hosts with/without virti= o-1, > > and some tests with pseries machines as well, and everything seems to > > work. > > = > > Thanks for the quick fix! > = > FYI what I think does not work is a recent kernel on 2.7 > machine type and host without virtio 1. > But this is not new. To clarify I was only testing migration compatibility, I assume virtio on 2.7 machines is still broken for the configuration you mentioned. The migration tests I ran on the virtio-1 host do cover networking over a virtio-net device before/after migration with reboots before/after migration as well though, and the guest in those cases had a 4.8 kernel, so I think the sanity checks I mentioned also apply for confirming virtio-net probe is succeeding in the guest. The non-virtio-1 runs are being done on my local machine and the tests in that case are a bit more basic and don't involve actively testing networking. I'll try some manual tests to check this. I guess the main things to confirm on that front are that after the patch virtio probing: pc-i440fx-2.6, defaults -> succeeds pc-i440fx-2.6, disable-modern=3Dtrue -> succeeds pc-i440fx-2.6, disable-modern=3Dfalse -> fails pc-i440fx-2.7, defaults -> fails pc-i440fx-2.7, disable-modern=3Dtrue -> succeeds pc-i440fx-2.7, disable-modern=3Dfalse -> fails pc-i440fx-2.8, defaults -> succeeds pc-i440fx-2.8, disable-modern=3Dtrue -> succeeds pc-i440fx-2.8, disable-modern=3Dfalse -> succeeds > = > > > --- > > > = > > > I'm not sure about the property name, let me know if you have better = ideas. > > > I didn't tested migration yet, but I wanted to share the patch while = I test it. > > > I tested booting v2.8 and v2.7 machines with !VERSION_1 and get expec= ted result: > > > - v2.8: Virtio-pci probe succeed > > > - v2.7: Virtio-pci probe fails > > > = > > > Thanks, > > > Maxime > > > = > > > hw/virtio/virtio-pci.c | 4 +++- > > > hw/virtio/virtio-pci.h | 1 + > > > include/hw/compat.h | 4 ++++ > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > = > > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > > > index 521ba0b..93f6b54 100644 > > > --- a/hw/virtio/virtio-pci.c > > > +++ b/hw/virtio/virtio-pci.c > > > @@ -1580,7 +1580,8 @@ static void virtio_pci_device_plugged(DeviceSta= te *d, Error **errp) > > > * Virtio capabilities present without > > > * VIRTIO_F_VERSION_1 confuses guests > > > */ > > > - if (!virtio_has_feature(vdev->host_features, VIRTIO_F_VERSION_1)= ) { > > > + if (!proxy->modern_broken && > > > + !virtio_has_feature(vdev->host_features, VIRTIO_F_VERSIO= N_1)) { > > > virtio_pci_disable_modern(proxy); > > > = > > > if (!legacy) { > > > @@ -1852,6 +1853,7 @@ static Property virtio_pci_properties[] =3D { > > > VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT, false), > > > DEFINE_PROP_BIT("page-per-vq", VirtIOPCIProxy, flags, > > > VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT, false), > > > + DEFINE_PROP_BOOL("x-modern-broken", VirtIOPCIProxy, modern_broke= n, false), > > > DEFINE_PROP_END_OF_LIST(), > > > }; > > > = > > > diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h > > > index b2a996f..1dca223 100644 > > > --- a/hw/virtio/virtio-pci.h > > > +++ b/hw/virtio/virtio-pci.h > > > @@ -153,6 +153,7 @@ struct VirtIOPCIProxy { > > > int config_cap; > > > uint32_t flags; > > > bool disable_modern; > > > + bool modern_broken; > > > OnOffAuto disable_legacy; > > > uint32_t class_code; > > > uint32_t nvectors; > > > diff --git a/include/hw/compat.h b/include/hw/compat.h > > > index 0f06e11..fe11723 100644 > > > --- a/include/hw/compat.h > > > +++ b/include/hw/compat.h > > > @@ -18,6 +18,10 @@ > > > .driver =3D "intel-iommu",\ > > > .property =3D "x-buggy-eim",\ > > > .value =3D "true",\ > > > + },{\ > > > + .driver =3D "virtio-pci",\ > > > + .property =3D "x-modern-broken",\ > > > + .value =3D "on",\ > > > }, > > > = > > > #define HW_COMPAT_2_6 \ > > > -- = > > > 2.9.3 > > > = >=20