Re: [RFC PATCH 4/4] firmware: arm_ffa: check pkvm initailised when initailise ffa driver

Yeoreum Yun
2026-04-23T10:57:58Z

Hi Will,

> On Wed, Apr 22, 2026 at 02:32:23PM +0100, Yeoreum Yun wrote:
> > Hi All,
> >
> > > > On Tue, Apr 21, 2026 at 07:57:43AM +0100, Yeoreum Yun wrote:
> > > >
> > > > [...]
> > > >
> > > > >
> > > > > Also, the FF-A initialization is not driven by a device probe, but rather
> > > > > happens as part of the bus registration itself,
> > > > > so it does not fit well with a device_link or probe deferral based approach.
> > > > >
> > > > > Instead, perhaps we could go with the idea I mentioned previously:
> > > > > either introduce a notifier, or create a pseudo ffa_device
> > > > > once pKVM initialization has completed, and
> > > > > then let the ffa driver perform the additional initialization from there.
> > > > >
> > > > > Am I missing something?
> > > > >
> > > >
> > > > In order to handle/cleanup some ugliness in interrupt management in the
> > > > FF-A driver, we may introduce DT node eventually. But it will take sometime.
> > >
> > > Unfortunately, I think this DT node wouldn't be helpful to solve
> > > this situation for dependency with the kvm misc device...
> > >
> > > IMHO, current situation, the notifier seems to good option. unless
> > > we make the initcall to recongise this dependency.
> > >
> >
> > I think the best approach for now is to introduce a notifier to handle this situation.
> > If there are no further suggestions, I’ll send a v2 based on:
> > - https://lore.kernel.org/all/aeS4rAeVQ0yJIPYw@e129823.arm.com/
>
> I can't say that I'm a huge fan of that :/
>
> The notifier will literally fire once, for a single listener. That's
> called a function call.

I revisited Marc’s suggestion about using device links
(https://lore.kernel.org/all/87pl3vb5bm.wl-maz@kernel.org/)

but unless I’m misunderstanding something, I don’t think it would be a viable solution:
- https://lore.kernel.org/all/aen0j3qM2k06OdXC@e129823.arm.com/#t

Also, calling functions defined by FF-A from KVM would introduce
an unnecessary module dependency between the KVM and FF-A drivers.

I’ve been trying to find an alternative approach,
but I’m not confident about what would be appropriate.

If you don’t mind, could you share your thoughts on this?

Thanks!

--
Sincerely,
Yeoreum Yun