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

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Message-ID: <e01513fb-8ed8-4d4b-9111-bbf8ac4cce89@kernel.org>
Date: Thu, 20 Nov 2025 09:49:19 +0000
From: Bryan O'Donoghue <bod@...nel.org>
To: Vikash Garodia <vikash.garodia@....qualcomm.com>,
 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 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.

---
bod