Re: [RFC PATCH v3 5/6] dt-bindings: of: Add restricted DMA pool

From: Florian Fainelli
Date: Thu Jan 07 2021 - 13:16:05 EST

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.