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Subject: Re: [RFC PATCH v3 5/6] dt-bindings: of: Add restricted DMA pool
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
 Claire Chang <tientzu@chromium.org>
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From: Florian Fainelli <f.fainelli@gmail.com>
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On 1/7/21 10:00 AM, Konrad Rzeszutek Wilk wrote:
>>>
>>>
>>>  - Nothing stops the physical device from bypassing the SWIOTLB buffer.
>>>    That is if an errant device screwed up the length or DMA address, the
>>>    SWIOTLB would gladly do what the device told it do?
>>
>> So the system needs to provide a way to lock down the memory access, e.g. MPU.
> 
> OK! Would it be prudent to have this in the description above perhaps?

Yes this is something that must be documented as a requirement for the
restricted DMA pool users, otherwise attempting to do restricted DMA
pool is no different than say, using a device private CMA region.
Without the enforcement, this is just a best effort.
-- 
Florian