[seL4] Re: new RFC: seL4 Device Driver Framework

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"William" == William ML Leslie writes:

William> On Mon, 17 Oct 2022 at 11:37, Demi Marie Obenour William> wrote:

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Will it be possible for clients to pre-register buffers with the multiplexer, and for the multiplexer to in turn register them with the driver? That would allow for devices to DMA directly to client buffers while still having the IOMMU restricting what the driver can do.

William> It seems that's what the framework should aim for - as in, William> don't do anything that precludes mapping pages directly for William> access by the device, where the hardware supports it. One of the things that needs to be evaluated is the cost of setting up and tearing down IOMMU mappings. For small transfers, copying the data may be cheaper. In any case, for things like network receive, the multiplexor is going to have to do a copy, to preserve inter-component privacy. You can't share a common DMA area for receive buffers if you want to prevent Component A seeing component B's traffic. Peter C -- Dr Peter Chubb https://trustworthy.systems/ Trustworthy Systems Group CSE, UNSW