linux-kernel - Re: [PATCH v3 0/6] media: iris: prepare support for video codecs on Qcom vpu4 platform

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Message-ID: <ccecc20e-0f5f-439b-861e-8313d76b0db6@oss.qualcomm.com>
Date: Fri, 21 Nov 2025 16:33:21 +0530
From: Vikash Garodia <vikash.garodia@....qualcomm.com>
To: Bryan O'Donoghue <bod@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vishnu Reddy <busanna.reddy@....qualcomm.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Vishnu Reddy <quic_bvisredd@...cinc.com>
Subject: Re: [PATCH v3 0/6] media: iris: prepare support for video codecs on
 Qcom vpu4 platform


On 11/20/2025 3:19 PM, Bryan O'Donoghue wrote:
> On 12/11/2025 05:09, Vikash Garodia wrote:
>>> One additional bonus is that fluster runs several process in parallel
>>> by default, catching issues caused by several decode threads running
>>> in parallel.
>>>
>> multi process issue is due to below [1] (tried it on lemans). Due to
>> higher concurrency, we can see that the DMA buffer is mapped into
>> un-addressable range (0-0x25800000) i.e 0x24b00000, and leading to
>> global fault. This was the reason i was keeping 2 memory-region in
>> kaanapali binding, to restrict certain ranges of IOVA.
> 
> If that is currently true then we should restrict concurrent sessions 
> entirely unless/until it can be safely supported.
> 

I would prefer to fix it than disable the feature. I would raising a fix 
for it.

Also, to keep it clear, this is nothing to do with this patch series. 
The issue about non usable IOVA range has been there for qcom vpu, it 
not newly introduced in iris driver. It was not exposed in venus and it 
is seen now in iris with concurrency when IOVA falls into that non 
addressable range.

Regards,
Vikash