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From:   Claire Chang <tientzu@chromium.org>
Date:   Tue, 12 Jan 2021 15:47:39 +0800
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Subject: Re: [RFC PATCH v3 5/6] dt-bindings: of: Add restricted DMA pool
To:     Florian Fainelli <f.fainelli@gmail.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Rob Herring <robh+dt@kernel.org>, mpe@ellerman.id.au,
        benh@kernel.crashing.org, paulus@samba.org,
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        Greg KH <gregkh@linuxfoundation.org>,
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On Fri, Jan 8, 2021 at 2:15 AM Florian Fainelli <f.fainelli@gmail.com> wrote:
>
> 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.

Will add in the next version.

> --
> Florian