On Fri, Jan 8, 2021 at 2:15 AM Florian Fainelli [off-list ref] wrote:

On 1/7/21 10:00 AM, Konrad Rzeszutek Wilk wrote:

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 - 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.

Will add in the next version.

--
Florian