Re: [Qemu-devel] [RFC] virtio-bus: Plug devices after features are negotiated

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 09/09/2016 05:39 PM, Michael S. Tsirkin wrote:
> On Fri, Sep 09, 2016 at 04:14:59PM +0200, Maxime Coquelin wrote:
>> > Currently, devices are plugged before features are negotiated.
>> > If the backend doesn't support VIRTIO_F_VERSION_1, the transport
>> > need to rewind some settings.
>> >
>> > This is the case for both PCI and CCW.
>> > For CCW, a post_plugged callback had been introduced, where
>> > max_rev field is just updated if VIRTIO_F_VERSION_1 is not
>> > supported by the backend.
>> > For PCI, implementing the post_plugged would be much more
>> > complicated, so the current fix consists in checking whether
>> > the backend supports VIRTIO_F_VERSION_1 in the backend.
>> >
>> > This patch propose to replace existing solutions with a common
>> > approach by negociating features before ->device_plugged() is
>> > called. A pre_plugged callback is introduced so that the
>> > transports can set their supported features.
>> >
>> > Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
>> > Cc: Marcel Apfelbaum <marcel@redhat.com>
>> > Cc: Michael S. Tsirkin <mst@redhat.com>
>> > Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>
> Looks good - can you pls test and post a non-RFC?
>

Do you mean having this also in stable, or keeping
it based on top of former pci-only patch?

I already tested it for PCI, but cannot test it for CCW.

Thanks,
Maxime