Re: [GIT PULL] iommu: Kill off pgsize_bitmap field from struct iommu_ops

[David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

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On Wed, 2015-04-01 at 15:39 +0100, Will Deacon wrote:
> 
> However, once we have that, we run into the same problem that we've got
> with the current pgsize_bitmap. Namely, that it needs to be a per-domain
> property to avoid it changing dynamically following an initial map request
> or a probe of a new IOMMU device.

That's not so much of a problem, surely? When adding devices to a new
domain without any mappings, the minimum page size of the domain is the
largest of all the IOMMUs participating in that domain.

And if you try to add new devices after you've already started making
mappings, we refuse the addition if it would raise the minimum page size
higher than the page sizes you're already using.

In VT-d we already have very similar logic for superpage and snooping
support.

-- 
dwmw2


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