Re: [virtio-comment] Re: [PATCH 10/11] transport-pci: Use driver notification PCI capability

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 12, 2023 at 05:24:57AM +0000, Parav Pandit wrote:
> 
> 
> > From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> > open.org> On Behalf Of Michael S. Tsirkin
> 
> > > Such registers do not start the VQ data path engines.
> > > 1.x spec has done the right thing to have dedicated notification region which
> > something an actual pci hw can implement.
> > 
> > okay so.. in fact it turns out existing hardware is not really happy to emulate
> > legacy. it does not really fit that well.
> > so maybe we should stop propagating the legacy interface to modern hardware
> > then.
> It is not about current hw, utilize what hw has to offer and utilize what sw has to offer.
> The key efficiency is coming by reusing what 1.x has already to offer.

Just ... no. Either run 0.X or 1.X. This mix opens a ton of corner
cases. NOTIFICATION_DATA is just off the top of my head, there's more
for sure.  It's a can of worms we won't be able to close.

> > Add the legacy net header size feature and be done with it.
> Hypervisor need to mediate and participate in all life cycle of the device.
> 
> One wants to run the block device too. Current proposal with other changes we discussed cover wider case.