On Fri, Nov 20, 2015 at 01:56:39PM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2015-11-19 at 23:38 +0000, David Woodhouse wrote:
> > 
> > I understand that POWER and other platforms don't currently have a
> > clean way to indicate that certain device don't have translation. And I
> > understand that we may end up with a *quirk* which ensures that the DMA
> > API does the right thing (i.e. nothing) in certain cases.
> > 
> > But we should *NOT* be involving the virtio device drivers in that
> > quirk, in any way. And putting a feature bit in the virtio device
> > itself doesn't seem at all sane either.
> > 
> > Bear in mind that qemu-system-x86_64 currently has the *same* problem
> > with assigned physical devices. It's claiming they're translated, and
> > they're not.
> 
> It's not that clear but yeah ... as I mentioned, I can't find a
> way to do that quirk that won't break when we want to actually use
> the iommu... 
> 
> Ben.

Yes, I am not at all sure we need a quirk for assigned devices.
Better teach QEMU to make iommu work for them.


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