Re: [Xen-devel] [RFC PATCH 2/9] iommu: Add ability to map/unmap the number of pages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.03.17 at 19:01, <olekstysh@xxxxxxxxx> wrote:
> Hi Jan
> 
> On Wed, Mar 22, 2017 at 5:44 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 15.03.17 at 21:05, <olekstysh@xxxxxxxxx> wrote:
>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>
>>> Extend the IOMMU code with new APIs and platform callbacks.
>>> These new map_pages/unmap_pages API do almost the same thing
>>> as existing map_page/unmap_page ones except the formers can
>>> handle the number of pages. So do new platform callbacks.
>>>
>>> Currently, this patch requires to modify neither
>>> existing IOMMU drivers nor P2M code.
>>> But, the patch might be rewritten to replace existing
>>> single-page stuff with the multi-page one followed by modifications
>>> of all related parts.
>>
>> Yes please. However, unless you strictly need a page count, please
>> instead use an "order" parameter. Doing that has been on my todo
>> list for quite a while.
> 
> The patch introduces new iommu_map_pages/iommu_unmap_pages APIs as well
> as new map_pages/unmap_pages platform callbacks.
> 
> So, we just need to replace single-page APIs with multi-page ones, but
> leave both "new" (map_pages/unmap_pages) and "old"
> (map_page/unmap_page) platform callbacks.
> This way doesn't require to modify existing IOMMU drivers right now,
> just P2M code. Or we need to replace platform callbacks too?

That was the "yes please" part of my answer: I don't see why we
would want two API / callback flavors, with one being a strict
superset of the other.

Jan


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