Re: [RFC PATCH 2/3] firmware: arm_ffa: initialise ff-a after finalising pKVM initialisation

[Yeoreum Yun <yeoreum.yun@arm.com>]

Hi Sudeep,

> On Tue, May 05, 2026 at 10:54:08AM +0100, Yeoreum Yun wrote:
> > When pKVM is enabled, the FF-A driver must be initialised after pKVM.
> > Otherwise, pKVM cannot negotiate the FF-A version or obtain the RX/TX
> > buffer information, leading to failures in FF-A calls.
> > 
> > Currently, pKVM initialisation completes at device_initcall_sync,
> > while ffa_init() runs at the device_initcall level.
> > 
> > So far, linker deployes kvm_arm_init() before ffa_init(), and SMCs can
> > still be trapped even before finalise_pkvm() is invoked.
> > As a result, this issue has not been observed.
> > 
> > However, relying on above stuff is fragile.
> > Therefore, when pKVM is enabled, the FF-A infrastructure should be
> > initialised only after pKVM initialisation has been fully finalised.
> > 
> > To achieve this, introduce an ffa_root_dev ("arm-ffa") and
> > a corresponding driver to defer initialisation of the FF-A infrastructure
> > until pKVM initialisation is complete, and to defer probing of all FF-A devices until then
> > when pKVM is enabled.
> > 
> 
> I don't like this whole ffa root device design.
> Two question for now:
> 1. Can FF-A be a module on systems with pKVM which removes the need for all
>    this dance done here ?

But this means we reduce the other feature e.x) IMA with TPM over
FF-A and pKVM feature. Since IMA must be a built-in, we couldn't avoid
to build FF-A driver with built-in.

> 2. If it is a requirement to have this built-in, I prefer to add a probe
>    and defer it instead of this root ffa device.

But, How? anyway all of FF-A device & driver couldn't be probed unless
FF-A initialisation is finished and How can we trigger FF-A initailise
after pKVM finish its initialisation?

The problem is ff-a intiailisation happens before pKVM finish its
initailasation and to do defer probe, it should use dd-model and
As we discussed in other thread, notifier couldn't be a soluation.

Could you let me share other way I'm missing?

Thanks!

> -- 
> Regards,
> Sudeep

-- 
Sincerely,
Yeoreum Yun