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Re: [RFC PATCH v3 5/6] dt-bindings: of: Add restricted DMA pool
- To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Claire Chang <tientzu@xxxxxxxxxxxx>
- From: Florian Fainelli <f.fainelli@xxxxxxxxx>
- Date: Thu, 7 Jan 2021 10:14:50 -0800
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- Cc: Rob Herring <robh+dt@xxxxxxxxxx>, mpe@xxxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, paulus@xxxxxxxxx, "list@xxxxxxx:IOMMU DRIVERS" <iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, joro@xxxxxxxxxx, will@xxxxxxxxxx, Frank Rowand <frowand.list@xxxxxxxxx>, boris.ostrovsky@xxxxxxxxxx, jgross@xxxxxxxx, sstabellini@xxxxxxxxxx, Christoph Hellwig <hch@xxxxxx>, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>, Robin Murphy <robin.murphy@xxxxxxx>, grant.likely@xxxxxxx, xypron.glpk@xxxxxx, Thierry Reding <treding@xxxxxxxxxx>, mingo@xxxxxxxxxx, bauerman@xxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>, Saravana Kannan <saravanak@xxxxxxxxxx>, rafael.j.wysocki@xxxxxxxxx, heikki.krogerus@xxxxxxxxxxxxxxx, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>, rdunlap@xxxxxxxxxxxxx, dan.j.williams@xxxxxxxxx, Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>, linux-devicetree <devicetree@xxxxxxxxxxxxxxx>, lkml <linux-kernel@xxxxxxxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, "list@xxxxxxx:IOMMU DRIVERS" <iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, Tomasz Figa <tfiga@xxxxxxxxxxxx>, Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
- Delivery-date: Thu, 07 Jan 2021 18:15:15 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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
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