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Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: David Woodhouse <dwmw2@infradead.org>,
        Andy Lutomirski <luto@amacapital.net>,
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Date: Fri, 20 Nov 2015 13:56:39 +1100
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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.