Date:	Fri, 19 Sep 2008 21:52:16 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] remove fullflush and nofullflush in IOMMU generic option

On Sat, Sep 20, 2008 at 03:48:11AM +0900, FUJITA Tomonori wrote:
> On Fri, 19 Sep 2008 20:01:18 +0200
> Joerg Roedel <joerg.roedel@....com> wrote:
> 
> > On Sat, Sep 20, 2008 at 02:40:35AM +0900, FUJITA Tomonori wrote:
> > > On Fri, 19 Sep 2008 19:30:04 +0200
> > > Joerg Roedel <joerg.roedel@....com> wrote:
> > > 
> > > > On Sat, Sep 20, 2008 at 02:09:21AM +0900, FUJITA Tomonori wrote:
> > > > > 
> > > > > Please keep it for AMD option for now. Please send a patch to make it
> > > > > generic to other IOMMU people and give them a chance to discuss on
> > > > > it.
> > > > >
> > > > 
> > > > Btw, you already agreed with a generic iommu= parameter for lazy IO/TLB
> > > > flushing"
> > > > 
> > > > 
> > > >  > True. We should merge common parameters across IOMMUs into the
> > > >  > iommu= parameter some time in the future, I think. It would also be the
> > > >  > place for the IOMMU size parameter.
> > > > 
> > > >  Hmm, now is better than the future? I think that now you can add
> > > >  something like 'disable_batching_flush' as a common parameter and
> > > >  change AMD IOMMU to use it.
> > > > 
> > > > in http://lkml.org/lkml/2008/9/17/376
> > > > 
> > > > And since we already have a iommu=fullflush parameter it makes sense of
> > > > make it generic.
> > > 
> > > I'm not against fullflush but we need to discuss it with other people
> > > before making the change.
> > 
> > Weird. Just 2 hours ago you wrote:
> > 
> > |http://lkml.org/lkml/2008/9/19/106
> > |
> > |For me, adding these boot parameters doesn't make sense.
> 
> See:
> 
> http://lkml.org/lkml/2008/9/19/221

Removing nofullflush and moving fullflush to the generic code are two
different questions. You talk about the first and I talk about the
second here. We should make sure we talk about the same things
when we flame each other ;)


> 
> > Anyway, I wrote to the Intel and Calgary developers and asked them for
> > their opinion. If they have real objections I am the last person NACKing
> > your original patch in this thread again.
> 
> I think that I already expressed a real objection for nofullflush
> twice though I'm not the maintainer of any IOMMUs.

And I agree with that. But AMD IOMMU updates are not the right place to
remove it.
 
> > The reason why I queued this patch in AMD IOMMU updates was that I
> > didn't wanted to implement an option specificly for AMD IOMMU when there
> > will be a generic one soon. This is double work I prefered to do it
> 
> You were not sure that they will be generic before discussion.

Since Intel has lazy flushing too it is generic enough. Its only the
question if the Intel VT-d maintainer want to use it.

Joerg

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