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

[Sudeep Holla <sudeep.holla@kernel.org>]

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 ?
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.

-- 
Regards,
Sudeep