On Thu, 23 Jul 2020 13:57:08 +0200 David Hildenbrand <da...@redhat.com> wrote:
> On 23.07.20 08:33, Cornelia Huck wrote: > > On Mon, 20 Jul 2020 11:07:51 +0200 > > David Hildenbrand <da...@redhat.com> wrote: > > > >> On 20.07.20 11:03, Michael S. Tsirkin wrote: > >>> 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. > >> > >> Makes sense, I suggest adding that to the patch description. > > > > "The list of devices supporting legacy is supposed to be static. We > > keep it in a central place to make sure that new devices do not enable > > legacy by accident." > > > > ? > > Ack! > > > > >> > >> Both patches look sane to me (- squashing them). > >> > > > > Patch 1 does not change behaviour, while patch 2 does (for > > virtio-iommu-pci). Still would like an opinion whether changing the > > behaviour for virtio-iommu-pci with no compat handling is ok. > > > > (I could be persuaded to squash them.) > > I'm a friend of introducing helper functions along with code that > actually uses it. But I agree that the change in behavior might be > hairy. Maybe we can split that out somehow to give it more attention? It should not really be noticeable for anything but virtio-iommu. However, I see these are already in a pull request...