Re: [PATCH 00 of 14] swiotlb/x86: lay groundwork for xen dom0 use of swiotlb

Jeremy Fitzhardinge
2008-12-18T20:09:27Z

Becky Bruce wrote:
> 32-bit powerpc needs this support - I was actually about to push a
> similar set of patches. We have several processors that support 36
> bits of physical address space and do not have any iommu capability.
> The rest of the kernel support for those processors is now in place,
> so swiotlb is the last piece of the puzzle for that to be fully
> functional. I need to take a closer look at this series to see
> exactly what it's doing and how it differs from what I've been testing.
>
> So there is another immediate use case, and I'd really hate to see
> this code duplicated. It should be entirely possible to remove the
> assumption that we can save off the VA of the original buffer, which
> is the thing that precludes HIGHMEM support, and still have nice
> readable, maintainable code.

Good, I'm glad I'm not just making things up ;)

The gist of the patch is to convert all the kernel virtual addresses
into struct page+offset. It's a fairly generic way to handle highmem
systems, so it should work for you too. Of course, if you have a
cleaner patch to achieve the same result, then we evaluate that too.

J