Re: [Qemu-stable] [PATCH v2 2/2] virtio-pci: Disable modern interface if backend without VIRTIO_F_VERSION_1

[Maxime Coquelin]

On 09/09/2016 07:48 PM, Michael S. Tsirkin wrote:
> On Fri, Sep 09, 2016 at 03:10:07PM +0200, Maxime Coquelin wrote:
> > This patch makes pci devices plugging more robust, by not confusing
> > guest with modern interface when the backend doesn't support
> > VIRTIO_F_VERSION_1.
> >
> > Cc: Cornelia Huck <address@hidden>
> > Cc: Marcel Apfelbaum <address@hidden>
> > Cc: Michael S. Tsirkin <address@hidden>
> > Cc: address@hidden
> > Signed-off-by: Maxime Coquelin <address@hidden>
> > ---
> >  hw/virtio/virtio-pci.c | 15 +++++++++++++++
> >  hw/virtio/virtio-pci.h |  5 +++++
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 755f921..9e88d7b 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1581,6 +1581,21 @@ static void virtio_pci_device_plugged(DeviceState *d, 
> > Error **errp)
> >      uint32_t size;
> >      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> >
> > +    /*
> > +     * Virtio capabilities present without
> > +     * VIRTIO_F_VERSION_1 confuses guests
> > +     */
> > +    if (!virtio_test_backend_virtio_1(vdev, errp)) {
> > +        virtio_pci_disable_modern(proxy);
> > +    }
> > +
> > +    legacy = virtio_pci_legacy(proxy);
> > +    modern = virtio_pci_modern(proxy);
> > +    if (!legacy && !modern) {
> > +        error_setg(errp, "PCI device is neither legacy nor modern.");
> > +        return;
> > +    }
> > +
>
> How does this interact with
>         virtio-pci: error out when both legacy and modern modes are disabled
> ?
> If it's the same, I'd rather pick that one and apply your
> change on top.
Not exactly, since with my patch modern can be disabled after realize
callback has been called.

But I will base my next revision on top of Greg's patch,
and use the same pattern as he did use.

Thanks,
Maxime