From: Alex Williamson
Date: Tue Mar 19 2013 - 23:18:49 EST

On Tue, 2013-03-19 at 20:08 -0700, H. Peter Anvin wrote:
> On 03/19/2013 07:48 PM, H. Peter Anvin wrote:
> > On 03/19/2013 06:28 PM, Matthew Garrett wrote:
> >> Mm. The question is whether we can reliably determine the ranges a
> device should be able to access without having to trust userspace
> (and, ideally, without having to worry about whether iommu vendors
> have done their job). It's pretty important for PCI passthrough, so we
> do need to care.
> >
> > It is actually very simple: the device should be able to DMA into/out of:
> >
> > 1. pinned pages
> > 2. owned by the process controlling the device
> >
> > ... and nothing else.
> >
> The "pinning" process needs to involve a call to the kernel to process
> the page for DMA (pinning the page and opening it in the iommu) and
> return a transaction address, of course.
> I think we have the interface for that in vfio, but I haven't followed
> that work.

Yes, vfio does this and is meant to provide a secure-boot-friendly PCI
passthrough interface. Thanks,


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