linux-kernel - Re: [PATCH v6 11/14] firmware: qcom_scm: Add qcom_scm_pas_get_rsc

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Message-ID: <20251107114955.zprgt2peq34im3ji@hu-mojha-hyd.qualcomm.com>
Date: Fri, 7 Nov 2025 17:19:55 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
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>,
        Manivannan Sadhasivam <mani@...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 v6 11/14] firmware: qcom_scm: Add
 qcom_scm_pas_get_rsc_table() to get resource table

On Fri, Nov 07, 2025 at 11:20:20AM +0100, Konrad Dybcio wrote:
> On 11/4/25 8:35 AM, Mukesh Ojha wrote:
> > Qualcomm remote processor may rely on Static and Dynamic resources for
> > it to be functional. Static resources are fixed like for example,
> > memory-mapped addresses required by the subsystem and dynamic
> > resources, such as shared memory in DDR etc., are determined at
> > runtime during the boot process.
> > 
> > For most of the Qualcomm SoCs, when run with Gunyah or older QHEE
> > hypervisor, all the resources whether it is static or dynamic, is
> > managed by the hypervisor. Dynamic resources if it is present for a
> > remote processor will always be coming from secure world via SMC call
> > while static resources may be present in remote processor firmware
> > binary or it may be coming qcom_scm_pas_get_rsc_table() SMC call along
> > with dynamic resources.
> 
> [...]
> 
> 
> > +	/*
> > +	 * TrustZone can not accept buffer as NULL value as argument Hence,
> > +	 * we need to pass a input buffer indicating that subsystem firmware
> > +	 * does not have resource table by filling resource table structure.
> > +	 */
> > +	if (!input_rt)
> > +		input_rt_size = sizeof(*rsc);
> 
> Would the expected size of the received data ever be any different
> than sizeof(*rsc) anyway?

input_rt_size != 0 and input_rt = NULL as input to this SCM call are 
invalid scenario.

Expected input_rt_size would be greater than sizeof(*rsc) if remote
processor firmware will have resource table section.


> 
> [...]
> 
> > +int qcom_scm_pas_get_rsc_table(struct qcom_scm_pas_context *ctx, void *input_rt,
> > +			       size_t input_rt_size, void **output_rt,
> > +			       size_t *output_rt_size)
> > +{
> > +	int ret;
> > +
> > +	do {
> > +		*output_rt = kzalloc(*output_rt_size, GFP_KERNEL);
> > +		if (!*output_rt)
> > +			return -ENOMEM;
> > +
> > +		ret = __qcom_scm_pas_get_rsc_table(ctx->pas_id, input_rt,
> > +						   input_rt_size, output_rt,
> > +						   output_rt_size);
> > +		if (ret)
> > +			kfree(*output_rt);
> > +
> > +	} while (ret == -EAGAIN);
> 
> This should at the very least be limited to a number of retries

Sure, how about 5 ?

> 
> Konrad

-- 
-Mukesh Ojha