On Fri, May 18, 2018 at 04:43:36PM -0500, Venu Busireddy wrote: > On 2018-05-18 17:06:23 +0100, Stefan Hajnoczi wrote: > > On Thu, May 17, 2018 at 09:06:04AM -0400, Venu Busireddy wrote: > > > > Can you describe a use case where vendor-specific extensions make sense > > as opposed to extending the VIRTIO specification? > > Sometimes, qemu may need to group certain devices together. In our > problem scenario, qemu needed to tell the driver which virtio device is a > fallback device for a given vfio-pci device. If the virtio device's PCI > capabilities are extended, the new capability could be used to store a > unique ID (say, the bus:device:function) that identifies the vfio-pci > device. The driver can use that information when needed to pair the > virtio device with the vfio-pci device.
This feature seems generic and could be in the VIRTIO spec proper. What is vendor-specific about it? > Extending the VIRTIO specification is also a good alternative, but > every time the vendor needs something new, the specification needs to > be changed again. A generic "vendor specific" mechanism alleviates that. If you plan to push Linux code changes upstream to implement this feature then a vendor-specific extension is inappropriate and you should extend the VIRTIO spec. Stefan
signature.asc
Description: PGP signature
