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

Sebastian Ene
2026-04-20T14:20:48Z

On Mon, Apr 20, 2026 at 01:46:47PM +0100, Marc Zyngier wrote:
> On Mon, 20 Apr 2026 13:32:32 +0100,
> Sebastian Ene <sebastianene@google.com> wrote:
> >
> > On Fri, Apr 17, 2026 at 06:57:59PM +0100, Yeoreum Yun wrote:
> >
> > Hello Yeoreum,
> >
> >
> > > When pKVM is enabled, the FF-A driver must be initialized after pKVM.
> > > Otherwise, pKVM cannot negotiate the FF-A version or
> > > obtain RX/TX buffer information, leading to failures in FF-A calls.
> >
> > At the moment this already happens after you move back ffa_init() to
> > device_initcall().
>
> But relying on this sort of ordering is just making things more
> fragile.
>

Thanks for letting me know. Since this is not a solid construct we will have
to change the driver init code to come after pKVM in this case.

> >
> > >
> > > During FF-A driver initialization, check whether pKVM has been initialized.
> > > If not, defer probing of the FF-A driver.
> > >
> >
> > I don't think you need to add this dependency. pKVM is
> > installed through KVM's module_init() which ends up calling hyp_ffa_init() to
> > do the proxy initialization. The ARM-FFA driver comes after it (since
> > pKVM is arch specific code). We don't have to call finalize_pkvm(..) to
> > be able to handle smc(FF-A) calls in the hyp-proxy.
>
> You do. Without the finalisation, SMCs are not trapped by EL2.
>
> And even if it did, relying on such hack is just wrong.
>

That makes it an even stronger argument to move the driver init at a
later stage. I was relying on this to trap early ff-a when the
ARM FF-A driver was used.

> M.
>
> --
> Without deviation from the norm, progress is not possible.

Thanks,
Sebastian