On Tue, Jul 20, 2021 at 12:48:43PM +0200, Cornelia Huck wrote: > On Tue, Jul 20 2021, Stefan Hajnoczi <[email protected]> wrote: > > > On Tue, Jul 20, 2021 at 11:04:55AM +0800, Jason Wang wrote: > >> Let me clarify, I agree we can't have a standard device state for all kinds > >> of device. > >> > >> That's way I tend to leave them to be device specific. (but not > >> implementation specific) > > > > Unfortunately device state is sometimes implementation-specific. Not > > because the device is proprietary, but because the actual state is > > meaningless to other implementations. > > > > I mentioned virtiofs as an example where file system backends can be > > implemented in completely different ways so the device state cannot be > > migrated between implementations. > > > >> But we can generalize the virtqueue state for sure. > > > > I agree and also that some device types can standardize their device > > state representations. But I think it's a technical requirement to > > support implementation-specific state for device types where > > cross-implementation migration is not possible. > > > > I'm not saying the implementation-specific state representation has to > > be a binary blob. There could be an identifier registry to ensure live > > migration compatibility checks can be performed. There could also be a > > standard binary encoding for migration data. But the contents will be > > implementation-specific for some devices. > > Can we at least put those implementation-specific states into some kind > of structured, standardized form? E.g. something like > > <type category: file system backend data> > <type identifier: file system foo> > <length> > <data> > > so that we can at least do compat checks for "I know how to handle foo"?
Yes, that's what I was trying to describe. Stefan
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