On 05/30/2010 04:03 PM, Michael S. Tsirkin wrote:

IMO this was because this driver does two things: programming iommu and
handling interrupts. uio does interrupt handling.
We could have moved iommu / DMA programming to
a separate driver, and have uio work with it.
This would solve limitation of the current driver
that is needs an iommu domain per device.


How do we enforce security then?  We need to ensure that unprivileged
users can only use the device with an iommu.

Force assigning to iommu before we allow any other operation?

That means the driver must be aware of the iommu.
The userspace driver? Yes. And It is a good thing to be explicit
there anyway, since this lets userspace map a non-contigious
virtual address list into a contiguous bus address range.

No, the kernel driver. It cannot allow userspace to enable bus mastering unless it knows the iommu is enabled for the device and remaps dma to user pages.


--
error compiling committee.c: too many arguments to function

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