linux-kernel - Re: [PATCH v4 06/12] firmware: qcom_scm: Add a prep version of auth_and

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Message-ID: <20251008073521.ky5cxxrxntundezl@hu-mojha-hyd.qualcomm.com>
Date: Wed, 8 Oct 2025 13:05:21 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 06/12] firmware: qcom_scm: Add a prep version of
 auth_and_reset function

On Tue, Oct 07, 2025 at 02:37:40PM -0700, Manivannan Sadhasivam wrote:
> On Tue, Oct 07, 2025 at 10:18:51PM +0530, Mukesh Ojha wrote:
> > For memory passed to TrustZone (TZ), it must either be part of a pool
> > registered with TZ or explicitly registered via SHMbridge SMC calls.
> > When Gunyah hypervisor is present, PAS SMC calls from Linux running at
> > EL1 are trapped by Gunyah running @ EL2, which handles SHMbridge
> > creation for both metadata and remoteproc carveout memory before
> > invoking the calls to TZ.
> > 
> > On SoCs running with a non-Gunyah-based hypervisor, Linux must take
> > responsibility for creating the SHM bridge before invoking PAS SMC
> > calls. For the auth_and_reset() call, the remoteproc carveout memory
> > must first be registered with TZ via a SHMbridge SMC call and once
> > authentication and reset are complete, the SHMbridge memory can be
> > deregistered.
> > 
> > Introduce qcom_scm_pas_prepare_and_auth_reset(), which sets up the SHM
> > bridge over the remoteproc carveout memory when Linux operates at EL2.
> > This behavior is indicated by a new field added to the PAS context data
> > structure. The function then invokes the auth_and_reset SMC call.
> > 
> > Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> > ---
> >  drivers/firmware/qcom/qcom_scm.c       | 48 ++++++++++++++++++++++++++++++++++
> >  include/linux/firmware/qcom/qcom_scm.h |  2 ++
> >  2 files changed, 50 insertions(+)
> > 
> > diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> > index 7b4ff3cb26ed..ab2543d44097 100644
> > --- a/drivers/firmware/qcom/qcom_scm.c
> > +++ b/drivers/firmware/qcom/qcom_scm.c
> > @@ -791,6 +791,54 @@ int qcom_scm_pas_auth_and_reset(u32 pas_id)
> >  }
> >  EXPORT_SYMBOL_GPL(qcom_scm_pas_auth_and_reset);
> >  
> > +/**
> > + * qcom_scm_pas_prepare_and_auth_reset() - Prepare, authenticate, and reset the
> > + *					   remote processor
> > + *
> > + * @ctx:	Context saved during call to qcom_scm_pas_context_init()
> > + *
> > + * This function performs the necessary steps to prepare a PAS subsystem,
> > + * authenticate it using the provided metadata, and initiate a reset sequence.
> > + *
> > + * It should be used when Linux is in control setting up the IOMMU hardware
> > + * for remote subsystem during secure firmware loading processes. The preparation
> > + * step sets up a shmbridge over the firmware memory before TrustZone accesses the
> > + * firmware memory region for authentication. The authentication step verifies
> > + * the integrity and authenticity of the firmware or configuration using secure
> > + * metadata. Finally, the reset step ensures the subsystem starts in a clean and
> > + * sane state.
> > + *
> > + * Return: 0 on success, negative errno on failure.
> > + */
> > +int qcom_scm_pas_prepare_and_auth_reset(struct qcom_scm_pas_context *ctx)
> > +{
> > +	u64 handle;
> > +	int ret;
> > +
> > +	if (!ctx->has_iommu)
> > +		return qcom_scm_pas_auth_and_reset(ctx->pas_id);
> > +
> > +	/*
> > +	 * When Linux running @ EL1, Gunyah hypervisor running @ EL2 traps the
> > +	 * auth_and_reset call and create an shmbridge on the remote subsystem
> > +	 * memory region and then invokes a call to TrustZone to authenticate.
> > +	 * When Linux runs @ EL2 Linux must create the shmbridge itself and then
> > +	 * subsequently call TrustZone for authenticate and reset.
> > +	 */
> > +	ret = qcom_tzmem_shm_bridge_create(ctx->mem_phys, ctx->mem_size, &handle);
> > +	if (ret) {
> > +		dev_err(__scm->dev, "Failed to create shmbridge ret=%d %u\n",
> 
> 	"Failed to create shmbridge for PAS ID (%u): %d\n"

Will apply, Thanks.

> 
> > +			ret, ctx->pas_id);
> > +		return ret;
> > +	}
> > +
> > +	ret = qcom_scm_pas_auth_and_reset(ctx->pas_id);
> > +	qcom_tzmem_shm_bridge_delete(handle);
> > +
> > +	return ret;
> 
> 	return 0;
> 
> - Mani
> 
> -- 
> மணிவண்ணன் சதாசிவம்

-- 
-Mukesh Ojha