Re: [PATCH 0/2] virtio: non-legacy device handling

[Michael S. Tsirkin]

On Mon, Jul 20, 2020 at 10:09:57AM +0200, David Hildenbrand wrote:
> On 07.07.20 12:54, Cornelia Huck wrote:
> > As discussed in "virtio-fs: force virtio 1.x usage", it seems like
> > a good idea to make sure that any new virtio device (which does not
> > support legacy virtio) is indeed a non-transitional device, just to
> > catch accidental misconfigurations. We can easily compile a list
> > of virtio devices with legacy support and have transports verify
> > in their plugged callbacks that legacy support is off for any device
> > not in that list.
> > 
> > Most new virtio devices force non-transitional already, so nothing
> > changes for them. vhost-user-fs-pci even does not allow to configure
> > a non-transitional device, so it is fine as well.
> > 
> > One problematic device, however, is virtio-iommu-pci. It currently
> > offers both the transitional and the non-transitional variety of the
> > device, and does not force anything. I'm unsure whether we should
> > consider transitional virtio-iommu unsupported, or if we should add
> > some compat handling. (The support for legacy or not generally may
> > change based upon the bus, IIUC, so I'm unsure how to come up with
> > something generic.)
> > 
> > Cornelia Huck (2):
> >   virtio: list legacy-capable devices
> >   virtio: verify that legacy support is not accidentally on
> 
> I'd squash both patches. Looking at patch #1, I wonder why we don't
> store that information along with the device implementation? What was
> the motivation to define this information separately?

Because people seem to cut and paste code, so when one
enables it in an old device, it gets pasted into a new one.
With a list in a central place, it's easier to figure out
what's going on.

> 
> -- 
> Thanks,
> 
> David / dhildenb