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SubjectRe: [PATCH 0/2] x86: per-device dma_mapping_ops
FUJITA Tomonori wrote:
> On Thu, 15 May 2008 11:01:09 +0200
> Andi Kleen <andi@firstfloor.org> wrote:
>
>> FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> writes:
>>
>>> This patchset adds per-device dma_mapping_ops support for
>>> CONFIG_X86_64 like POWER architecture does. This change enables us to
>>> cleanly fix the Calgary IOMMU issue that some devices are not behind
>>> the IOMMU [1]. It also would be helpful to handle KVM PCI passthrough.
>> This makes it basically impossible to do stack ops, which some
>> people have been doing.
>
> Seems that I misunderstand what those people want.
>
> What those people want to do and how the stack ops achieve it? Or can
> you tell me where their patches are?

I've seen it in two cases: first was for KVM IO bypass and the other was a
(unfinished) patch to support the NoDMA bitmaps on some systems.

In this case you really want to do a wrapper around the existing ops
and extend the mapping.

That worked fine by just replacing the global pointer, but will
be quite hard in your set up.

-Andi




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