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

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Message-ID: <f4595a18-23bd-d54f-4e50-c0ed63008225@quicinc.com>
Date:   Wed, 14 Dec 2022 16:03:50 +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 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.

- Sibi

> 
>> +		node = of_parse_phandle(child, "memory-region", 0);
>> +		of_node_put(child);
>> +	}
>> +
>> +	if (!node)
>> +		return 0;
>> +
>> +	ret = of_address_to_resource(node, 0, &r);
>> +	of_node_put(node);
>> +	if (ret) {
>> +		dev_err(qproc->dev, "unable to resolve metadata region\n");
>> +		return ret;
>> +	}
>> +
>> +	qproc->mdata_phys = r.start;
>> +
>>   	return 0;
>>   }
>>   
> 
> Best regards,
> Krzysztof
>