Use the default subsystem vendor ID for virtio devices (Mark McLoughlin)

Use the default subsystem vendor ID for virtio  devices (Mark McLoughlin)

A subsystem vendor ID of zero isn't allowed, so we use our
default ID.

Gerd points out that although the PCI subsystem vendor ID is
treated by the guest as the virtio vendor ID:

   /* we use the subsystem vendor/device id as the virtio vendor/device
    * id.  this allows us to use the same PCI vendor/device id for all
    * virtio devices and to identify the particular virtio driver by
    * the subsytem ids */
    vp_dev->vdev.id.vendor = pci_dev->subsystem_vendor;
    vp_dev->vdev.id.device = pci_dev->subsystem_device;

it looks like only the device ID is used right now:

   # grep virtio modules.alias
   alias virtio:d00000001v* virtio_net
   alias virtio:d00000002v* virtio_blk
   alias virtio:d00000003v* virtio_console
   alias virtio:d00000004v* virtio-rng
   alias virtio:d00000005v* virtio_balloon
   alias pci:v00001AF4d*sv*sd*bc*sc*i* virtio_pci
   alias virtio:d00000009v* 9pnet_virtio

so setting the subsystem vendor id to something != zero shouldn't cause
trouble.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6440 c046a42c-6fe2-441c-8c8c-71466251a162