linux-kernel - Re: [PATCH 2/2] firmware: arm_scmi: optee: use optee system invocation

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Message-ID: <CAFA6WYOgFqKiS8BXaxtc-4cc3zZkRcTGX3PGqzShCAuP1OZDGA@mail.gmail.com>
Date:   Tue, 7 Feb 2023 16:41:34 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Jens Wiklander <jens.wiklander@...aro.org>
Cc:     Etienne Carriere <etienne.carriere@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi <cristian.marussi@....com>
Subject: Re: [PATCH 2/2] firmware: arm_scmi: optee: use optee system invocation

On Tue, 7 Feb 2023 at 16:09, Jens Wiklander <jens.wiklander@...aro.org> wrote:
>
> On Tue, Feb 7, 2023 at 10:59 AM Sumit Garg <sumit.garg@...aro.org> wrote:
> >
> > On Mon, 30 Jan 2023 at 15:12, Etienne Carriere
> > <etienne.carriere@...aro.org> wrote:
> > >
> > > Changes SCMI optee transport to enable sys_service capability of
> > > its tee context to leverage provisioned system resources in OP-TEE
> > > preventing possible deadlock.
> > >
> > > Such deadlock could happen when many Linux clients invoke OP-TEE are
> > > are all suspended waiting for an OP-TEE RPC request access an SCMI
> > > resource through the SCMI OP-TEE PTA service.
> > >
> > > Signed-off-by: Etienne Carriere <etienne.carriere@...aro.org>
> > > ---
> > >  drivers/firmware/arm_scmi/optee.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/firmware/arm_scmi/optee.c b/drivers/firmware/arm_scmi/optee.c
> > > index 2a7aeab40e54..91840345e946 100644
> > > --- a/drivers/firmware/arm_scmi/optee.c
> > > +++ b/drivers/firmware/arm_scmi/optee.c
> > > @@ -559,6 +559,9 @@ static int scmi_optee_service_probe(struct device *dev)
> > >         if (IS_ERR(tee_ctx))
> > >                 return -ENODEV;
> > >
> > > +       /* SCMI agent can used TEE system service resources */
> > > +       tee_ctx->sys_service = true;
> > > +
> >
> > As per the other thread for patch #1, this feature will only be
> > available with OP-TEE supporting TEE_GEN_CAP_REG_MEM. Can we add a
> > corresponding conditional check here?
>
> What would be gained by that? If a system thread isn't available or
> already is busy we're supposed to fall back to normal threads.
>

Just to make the dependency explicit and probably warn users that the
system is missing a required capability. Earlier I went through a
similar dependency issue report for trusted keys driver. I ended with
a dependency fix [1] to make it easier while debugging when something
doesn't work as intended.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/security/keys/trusted-keys/trusted_tee.c#n223

-Sumit

> Cheers,
> Jens
>
> >
> > -Sumit
> >
> > >         agent = devm_kzalloc(dev, sizeof(*agent), GFP_KERNEL);
> > >         if (!agent) {
> > >                 ret = -ENOMEM;
> > > --
> > > 2.25.1
> > >