linux-kernel - Re: [PATCH v2 5/8] dt-bindings: misc: add property to support non-secure DSP

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Message-ID: <ac2e9f8f-ea52-5676-baaa-9439e8b35d8f@linaro.org>
Date:   Mon, 13 Dec 2021 12:35:40 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     robh+dt@...nel.org, gregkh@...uxfoundation.org,
        devicetree@...r.kernel.org, ekangupt@....qualcomm.com,
        jeyr@...eaurora.org, bkumar@....qualcomm.com,
        linux-kernel@...r.kernel.org, bjorn.andersson@...aro.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 5/8] dt-bindings: misc: add property to support
 non-secure DSP



On 13/12/2021 10:57, Stephan Gerhold wrote:
> On Thu, Dec 09, 2021 at 12:06:23PM +0000, Srinivas Kandagatla wrote:
>> From: Jeya R <jeyr@...eaurora.org>
>>
>> Add property to set DSP domain as non-secure.
>>
>> ADSP/MDSP/SDSP are by default secured, where as CDSP can be either be
>> secured/unsecured.
> 
> Wouldn't it be easier to avoid the negation and add a "qcom,secure-domain"
> property instead? Given PATCH 8/8 ("arm64: dts: qcom: add non-secure
> domain property to fastrpc nodes") it looks like you are intentionally
> breaking DT compatibility here, but this patch does not justify why this
> is necessary.

By default all ADSP/MDSP/SDSP are secured, so this property is only 
required for something that is not default. Only case that is 
configurable is the CDSP case where in by adding this flag we should be 
able to load an unsigned process to dsp using unsecured node.

Having said that, TBH When we first added the fastrpc patchset we did 
not take care of this security feature properly :-)

 From security point of view, its better to keep the default as secured 
rather than unsecured in DT too.

With this DTS patch older dts should continue to work.

--srini

> 
> Thanks,
> Stephan
>