Re: [PATCH v3 24/24] vfio/migration: Multifd device state transfer support - send side

[Maciej S. Szmigiero]

On 13.12.2024 12:08, Cédric Le Goater wrote:
> > > > By the way, this kind of an implicit dependency in VMState between devices
> > > > is really hard to manage, there should be a way to specify it in code somehow..
> > >
> > > vmstate has a MigrationPriority field to order loading between
> > > devices. Maybe we could extend but I think it is better to handle
> > > ordering at the device level when there are no external dependencies.
> > > It should be well documented though in the code.
> >
> > To be clear, by "handling ordering at the device level" you mean
> > just disabling this functionality for ARM64 as proposed above?
>
> I meant handling the migration ordering in the device load/save
> handlers without making assumptions on other devices.
>
> Regarding ARM64, it would be unfortunate to deactivate the feature
> since migration works correctly today, on AMR64 64k kernels too,
> and this series should improve also downtime. Support can be added
> gradually though.

I wasn't thinking about disabling the whole multifd migration support
in VFIO on ARM64, but just the config state transfer part.

While adding a proper migration device ordering is probably a good
future goal it's not quite fitting this patch set scope.

> Thanks,
>
> C.

Thanks,
Maciej