linux-kernel - Re: [PATCH v2 10/11] remoteproc: qcom: pas: Enable Secure PAS support with IOMMU managed by Linux

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Message-ID: <20250820120359.dsdbm5txyrsdbedy@hu-mojha-hyd.qualcomm.com>
Date: Wed, 20 Aug 2025 17:33:59 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-media@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH v2 10/11] remoteproc: qcom: pas: Enable Secure PAS
 support with IOMMU managed by Linux

On Wed, Aug 20, 2025 at 10:40:25AM +0200, Stephan Gerhold wrote:
> On Tue, Aug 19, 2025 at 10:24:45PM +0530, Mukesh Ojha wrote:
> > Most Qualcomm platforms feature a proprietary hypervisor (such as Gunyah
> > or QHEE), which typically handles IOMMU configuration. This includes
> > mapping memory regions and device memory resources for remote processors
> > by intercepting qcom_scm_pas_auth_and_reset() calls. These mappings are
> > later removed during teardown. Additionally, SHM bridge setup is
> > required to enable memory protection for both remoteproc metadata and
> > its memory regions.
> > 
> > When the aforementioned hypervisor is absent, the operating system must
> > perform these configurations instead.
> > 
> > When Linux runs as the hypervisor (at EL2) on a SoC, it will have its
> > own device tree overlay file that specifies the firmware stream ID now
> > managed by Linux for a particular remote processor. If the iommus
> > property is specified in the remoteproc device tree node, it indicates
> > that IOMMU configuration must be handled by Linux. In this case, the
> > has_iommu flag is set for the remote processor, which ensures that the
> > resource table, carveouts, and SHM bridge are properly configured before
> > memory is passed to TrustZone for authentication. Otherwise, the
> > has_iommu flag remains unset, which is the default behavior.
> > 
> > Enables Secure PAS support for remote processors when IOMMU configuration
> > is managed by Linux.
> > 
> > Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> > ---
> >  drivers/remoteproc/qcom_q6v5_pas.c | 63 +++++++++++++++++++++++++++---
> >  1 file changed, 57 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/remoteproc/qcom_q6v5_pas.c b/drivers/remoteproc/qcom_q6v5_pas.c
> > index 1e0f09bf1ef2..180528bcd57c 100644
> > --- a/drivers/remoteproc/qcom_q6v5_pas.c
> > +++ b/drivers/remoteproc/qcom_q6v5_pas.c
> > [...]
> > @@ -424,7 +459,8 @@ static int qcom_pas_parse_firmware(struct rproc *rproc, const struct firmware *f
> >  	if (!rproc->has_iommu)
> >  		return ret;
> >  
> > -	ret = qcom_scm_pas_get_rsc_table(pas->pas_id, NULL, 0, &output_rt, &output_rt_size);
> > +	ret = qcom_scm_pas_get_rsc_table(pas->pas_ctx, NULL, 0,
> > +					 &output_rt, &output_rt_size);
> 
> Unrelated formatting change, should be in previous commit.

Ack, will fix.

> 
> >  	if (ret) {
> >  		dev_err(pas->dev, "error %d getting resource_table\n", ret);
> >  		return ret;
> > @@ -726,6 +762,20 @@ static int qcom_pas_probe(struct platform_device *pdev)
> >  		return -ENOMEM;
> >  	}
> >  
> > +	if (of_property_present(pdev->dev.of_node, "iommus")) {
> 
> I think you need a dt-bindings change for this? You had one in v1, but
> dropped it entirely for some reason.

I missed to mentioned it in changelog.

As I said in another patch, I intended to send it separately however,
will send it along with this series in the next version.

> 
> > +		struct of_phandle_args args;
> > +
> > +		ret = of_parse_phandle_with_args(pdev->dev.of_node, "iommus",
> > +						 "#iommu-cells", 0, &args);
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		rproc->has_iommu = true;
> > +		of_node_put(args.np);
> > +	} else {
> > +		rproc->has_iommu = false;
> > +	}
> > +
> >  	rproc->auto_boot = desc->auto_boot;
> >  	rproc_coredump_set_elf_info(rproc, ELFCLASS32, EM_NONE);
> >  
> > @@ -800,6 +850,7 @@ static int qcom_pas_probe(struct platform_device *pdev)
> >  	if (!pas->dtb_pas_ctx)
> >  		goto remove_ssr_sysmon;
> >  
> > +	pas->pas_ctx->has_iommu = pas->dtb_pas_ctx->has_iommu = rproc->has_iommu;
> 
> Nitpick: I think this would look cleaner if you separate it into two
> lines (only one assignment on each line).
> 

Sure.

Thanks for the review.

> Thanks,
> Stephan

-- 
-Mukesh Ojha