linux-kernel - Re: [PATCH v8 11/14] firmware: qcom_scm: Add qcom_scm_pas_get_rsc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251208142517.wdve2btbcvn2dmq3@hu-mojha-hyd.qualcomm.com>
Date: Mon, 8 Dec 2025 19:55:17 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        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 v8 11/14] firmware: qcom_scm: Add
 qcom_scm_pas_get_rsc_table() to get resource table

On Fri, Dec 05, 2025 at 04:21:07PM -0600, Bjorn Andersson wrote:
> On Mon, Nov 24, 2025 at 08:55:38PM +0530, Mukesh Ojha wrote:
> > On Mon, Nov 24, 2025 at 12:48:31PM +0100, Konrad Dybcio wrote:
> > > On 11/21/25 12:01 PM, 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.
> > > > 
> > > > Some of the remote processor drivers, such as video, GPU, IPA, etc., do
> > > > not check whether resources are present in their remote processor
> > > > firmware binary. In such cases, the caller of this function should set
> > > > input_rt and input_rt_size as NULL and zero respectively. Remoteproc
> > > > framework has method to check whether firmware binary contain resources
> > > > or not and they should be pass resource table pointer to input_rt and
> > > > resource table size to input_rt_size and this will be forwarded to
> > > > TrustZone for authentication. TrustZone will then append the dynamic
> > > > resources and return the complete resource table in output_rt
> > > > 
> > > > More about documentation on resource table format can be found in
> > > > include/linux/remoteproc.h
> > > > 
> > > > Signed-off-by: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
> > > > ---
> > > 
> > > [...]
> > > 
> > > > +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)
> > > > +{
> > > > +	unsigned int retry_num = 5;
> > > > +	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 && --retry_num);
> > > 
> > > Will firmware return -EAGAIN as a result, or is this to handle the
> > > "buffer too small case"?
> > 
> > The latter one where a re-attempt could pass..
> > 
> 
> But why would we need more than 1 retry here? In what cases do we expect
> that the first attempt is too small, and then the next 4 attempts are
> also going to be too small?
> 
> Why is 5 a good number?

This was a misunderstanding, will fix it as per latest discussion.

-- 
-Mukesh Ojha