Re: [Qemu-devel] [PATCH RFC] fixup! virtio: convert to use DMA api

[David Woodhouse <dwmw2@infradead.org>]

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On Mon, 2016-04-18 at 16:12 +0300, Michael S. Tsirkin wrote:
> I'm not sure I understand the issue.  The public API is not about how
> the driver works.  It doesn't say "don't use DMA API" anywhere, does it?
> It's about telling device whether to obey the IOMMU and
> about discovering whether a device is in fact under the IOMMU.

Apologies, I was wrongly reading this as a kernel patch.

After a brief struggle with "telling device whether to obey the IOMMU",
which is obviously completely impossible from the guest kernel, I
realise my mistake :)

So... on x86 how does this get reflected in the DMAR tables that the
guest BIOS presents to the guest kernel, so that the guest kernel
*knows* which devices are behind which IOMMU?

(And are you fixing the case of assigned PCI devices, which aren't
behind any IOMMU, at the same time as you answer that? :)

-- 
dwmw2



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