RE: [PATCH v4 0/4] Implement vdpasim stop operation

[Parav Pandit]

> From: Jason Wang <jasowang@xxxxxxxxxx>
> Sent: Tuesday, May 31, 2022 10:42 PM
> 
> Well, the ability to query the virtqueue state was proposed as another
> feature (Eugenio, please correct me). This should be sufficient for making
> virtio-net to be live migrated.
> 
The device is stopped, it won't answer to this special vq config done here.
Programming all of these using cfg registers doesn't scale for on-chip memory and for the speed.

Next would be to program hundreds of statistics of the 64 VQs through giant PCI config space register in some busy polling scheme.

I can clearly see how all these are inefficient for faster LM.
We need an efficient AQ to proceed with at minimum.

> https://lists.oasis-open.org/archives/virtio-comment/202103/msg00008.html
> 
> > Once the device is stopped, its state cannot be queried further as device
> won't respond.
> > It has limited use case.
> > What we need is to stop non admin queue related portion of the device.