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

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

Hi Sebastian,

> On Mon, Apr 20, 2026 at 02:00:57PM +0100, Yeoreum Yun wrote:
>
> Hi,
>
> >
> > Hi Sebastian,
> > > 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().
> >
> > How? the kvm_arm_init() is device_initcall() if both built as built-in.
> >
> > >
> > > >
> > > > 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.
> > >
> >
> > As Marc said, the before finalised_pkvm(), smc wouldn't be trapped
> > to pKVM. IOW, in case when both built as built-in,
>
> They are, I tested before replying to this thread. The HCR_EL2 is
> 0x480080000 so HCR_EL2 TSC bit is set so SMC/FF-A and trapping is enabled.

Oh. I've missed cpu_init_hyp_mode() sets up HCR_EL2. So you're right.
Thanks to correct me ;)

>
> In __pkvm_prot_finalize it sets the HCR_VM bit which enables stage-2 and
> then write the HCR_EL2 from params->hcr_el2. However I wasn't sure that
> this is seen as a 'hack' and not expected to work.
>
> > if ffa_init() is called before finalised_pkvm(),
> > it couldn't proxy the FFA_VERSION, FFA_RXTX_MAP and FFA_PARTITION_INFO_GET
> > called by ffa_init().
> >
> > How can you gurantee hyp_ffa_init() which is called by kvm_arm_init()
> > comes first even kvm_arm_init() and ffa_init() are on device_initcall?
> >
>
> While they are both on device_initcall, the only difference is that
> kvm_arm_init is arch code which appears before the driver/ code in the
> linker. That's why Marc said it is not a solid construct to rely on
> this.

Then I think the origin one -- just check kvm_arm_initialised
is enough to check in ffa_driver. since I misunderstood TSC bit
is setup after finalised_pkvm().

or Am I missing something?

Thanks.

--
Sincerely,
Yeoreum Yun