linux-kernel - Re: [PATCH v4 06/11] firmware: qcom: scm: remove unused arguments to the shm

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Message-ID: <2a0df02a-1657-4b59-8f31-791a8aff523e@oss.qualcomm.com>
Date: Tue, 6 May 2025 09:18:49 +1000
From: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
To: Kuldeep Singh <quic_kuldsing@...cinc.com>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Apurupa Pattapu <quic_apurupa@...cinc.com>,
        Kees Cook <kees@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>
Cc: linux-arm-msm@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v4 06/11] firmware: qcom: scm: remove unused arguments to
 the shm_brige



On 5/5/2025 8:58 PM, Kuldeep Singh wrote:
> 
> 
> On 4/29/2025 11:36 AM, Amirreza Zarrabi wrote:
>> shm_bridge create/delete functions always use the scm device.
>> There is no need to pass it as an argument.
>>
>> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
> 
> 
> There are 2 type of APIs exposed by tzmem driver for pool creation.
> devm_qcom_tzmem_pool_new and qcom_tzmem_pool_new.
> 
> Device managed pool is created with devm_qcom_tzmem_pool_new but
> currently qcom_scm is using it's own dev to create/delete bridge which
> is problamatic here.
> 
> https://elixir.bootlin.com/linux/v6.14.5/source/drivers/firmware/qcom/qcom_scm.c#L1653
> 
> If pool is device managed, same dev should be used in qcom_scm to
> create/delete bridge rather than using qcom_scm dev.
> The dev passed as an argument to function should be used instead of
> __scm->dev.
> https://elixir.bootlin.com/linux/v6.14.5/source/drivers/firmware/qcom/qcom_scm.c#L1634
> 
> To summarize, I believe correct solution should be to pass corresponding
> dev to bridge create/delete APIs instead of always assuming to be
> qcom_scm dev for devm_qcom_tzmem_pool_new scenarios.
> For qcom_tzmem_pool_new, qcom_scm/qcom_tzmem_dev can be used.
> 
> Bartosz/Amirreza, please share your thoughts as well.
> 

It is not true.
Why should shmbridge need to have access to random devices, while the resources
are obtained from the scm device, if any?

- Amir