linux-kernel - Re: [PATCH 4/4] remoteproc: qcom_q6v5_mss: Use a carveout to authenticate modem headers

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Date:   Wed, 14 Dec 2022 17:21:06 +0530
From:   Sibi Sankar <quic_sibis@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <andersson@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <robh+dt@...nel.org>, <manivannan.sadhasivam@...aro.org>
CC:     <agross@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <konrad.dybcio@...ainline.org>, <amit.pundir@...aro.org>,
        <regressions@...mhuis.info>, <sumit.semwal@...aro.org>,
        <will@...nel.org>, <catalin.marinas@....com>,
        <robin.murphy@....com>
Subject: Re: [PATCH 4/4] remoteproc: qcom_q6v5_mss: Use a carveout to
 authenticate modem headers



On 12/14/22 16:58, Krzysztof Kozlowski wrote:
> On 14/12/2022 11:33, Sibi Sankar wrote:
>>
>>
>> On 12/14/22 01:17, Krzysztof Kozlowski wrote:
>>> On 13/12/2022 15:07, Sibi Sankar wrote:
>>>> The memory region allocated using dma_alloc_attr with no kernel mapping
>>>> attribute set would still be a part of the linear kernel map. Any access
>>>> to this region by the application processor after assigning it to the
>>>> remote Q6 will result in a XPU violation. Fix this by replacing the
>>>> dynamically allocated memory region with a no-map carveout and unmap the
>>>> modem metadata memory region before passing control to the remote Q6.
>>>>
>>>> Reported-by: Amit Pundir <amit.pundir@...aro.org>
>>>> Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for mem ownership switch")
>>>> Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
>>>> ---
>>>
>>> Thank you for your patch. There is something to discuss/improve.
>>>>    
>>>>    	return ret < 0 ? ret : 0;
>>>> @@ -1882,6 +1899,26 @@ static int q6v5_alloc_memory_region(struct q6v5 *qproc)
>>>>    	qproc->mpss_phys = qproc->mpss_reloc = r.start;
>>>>    	qproc->mpss_size = resource_size(&r);
>>>>    
>>>> +	if (!child) {
>>>> +		node = of_parse_phandle(qproc->dev->of_node, "memory-region", 2);
>>>> +	} else {
>>>> +		child = of_get_child_by_name(qproc->dev->of_node, "metadata");
>>>
>>> Bindings do not allow to have child "metadata", do they?
>>
>> memory-region property was used to specify mba/mpss region in a phandle
>> array only from SC7180 SoC. All the older dtbs in the wild/upstream
>> still had sub-nodes to achieve the same. Patch 3 allows for a sub-set
>> of the SoCs (MSM8996/MSM8998/SDM845) to use metadata as a sub-node so
>> as to not break bindings when newer kernel uses a older dtb.
> 
> This does not explain why you extend the driver without extending the
> bindings. You do not do it for legacy stuff but for SC7180. But even for
> legacy devices you cannot add new properties without having it in some
> legacy bindings.

https://patchwork.kernel.org/project/linux-arm-msm/patch/20221213140724.8612-4-quic_sibis@quicinc.com/

The legacy bindings are a part of patch 3 ^^.

> 
> 
> Best regards,
> Krzysztof
>