linux-kernel - Re: [PATCH 2/4] firmware: qcom: scm: take struct device as argument in SHM bridge enable

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Message-ID: <b1db543e-f33e-4162-8de1-257084d282de@oss.qualcomm.com>
Date: Wed, 25 Jun 2025 14:08:48 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Bartosz Golaszewski <brgl@...ev.pl>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 2/4] firmware: qcom: scm: take struct device as argument
 in SHM bridge enable

On 6/25/25 10:14 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> qcom_scm_shm_bridge_enable() is used early in the SCM initialization
> routine. It makes an SCM call and so expects the internal __scm pointer
> in the SCM driver to be assigned. For this reason the tzmem memory pool
> is allocated *after* this pointer is assigned. However, this can lead to
> a crash if another consumer of the SCM API makes a call using the memory
> pool between the assignment of the __scm pointer and the initialization
> of the tzmem memory pool.
> 
> As qcom_scm_shm_bridge_enable() is a special case, not meant to be
> called by ordinary users, pull it into the local SCM header. Make it
> take struct device as argument. This is the device that will be used to
> make the SCM call as opposed to the global __scm pointer. This will
> allow us to move the tzmem initialization *before* the __scm assignment
> in the core SCM driver.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---

I think you'll most definitely want to leave some comment about this
intertwined chain, or someone is sure to break it in the future when
doing some sort of refactoring

Konrad