Re: [PATCH 0/2] x86: per-device dma_mapping_ops

[FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>]

On Fri, 16 May 2008 07:24:33 +0200
Andi Kleen <andi@firstfloor.org> wrote:

> FUJITA Tomonori wrote:
> > On Thu, 15 May 2008 12:48:04 +0200
> > Andi Kleen <andi@firstfloor.org> wrote:
> > 
> >>> I thought that KVM people want to do it per device (in the first
> >>> case). So with my patchse, they can replace the dma_ops pointer in
> >>> dev_archdata with what they want.
> >> But where would they save the original pointer?
> > 
> > Yeah, we need an extra mechanism for that but it's same for the
> > system-wide dma_ops pointer (i.e. without my patches), isn't it?
> > 
> > I'm still not sure how this patchset make it impossible to have stack
> > dma_ops. These people need per-device dma_ops and we can do stack
> > per-device dma_ops?
> 
> Anybody who does stack ops in your scheme would need to hook into new
> device creation and an own per device saving pointer. Also there
> are livetime issues when to wrap.

But is that what those people want, setting up dma_ops per device?

I think that creating a hook is not difficult and we could put a
mechnism to save a pointer in asm-x86/{dma-mapping.h, device.h}.

 
> It's certainly possible, but likely complicated

Hmm, let's see what those people think about on this. I'll repost a
patchset for -mm with CC'ing those people.