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Message-ID: <20081218210231.GB24271@elte.hu>
Date: Thu, 18 Dec 2008 22:02:31 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Becky Bruce <beckyb@...nel.crashing.org>
Cc: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
Jeremy Fitzhardinge <jeremy@...p.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
xen-devel@...ts.xensource.com, x86@...nel.org,
ian.campbell@...rix.com, jbeulich@...ell.com, joerg.roedel@....com,
Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 00 of 14] swiotlb/x86: lay groundwork for xen dom0 use
of swiotlb
* Becky Bruce <beckyb@...nel.crashing.org> wrote:
>> Can you be more specific? What architecture is plan to use highmem
>> support in swiotlb?
>
> 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.
you can have a look at Jeremy's current lineup of patches in
tip/core/iotlb:
http://people.redhat.com/mingo/tip.git/README
(also integrated into tip/master)
What would be needed to make it suit your usecase too?
Ingo
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