linux-kernel - Re: [PATCH] x86-64: disable the GART before allocate aperture

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Message-ID: <20070623003530.GA4505@rhun.smartcity.com>
Date:	Fri, 22 Jun 2007 17:35:30 -0700
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Yinghai Lu <Yinghai.Lu@....COM>
Cc:	Andi Kleen <ak@...e.de>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86-64: disable the GART before allocate aperture

On Fri, Jun 22, 2007 at 05:27:50PM -0700, Yinghai Lu wrote:
> Andi Kleen wrote:
> >On Saturday 23 June 2007 00:19:51 Alan Cox wrote:
> >The kdump kernel should be normally all <4GB anyways. You won't
> >need any IOMMU for its IO unless you O_DIRECT/sendfile out of /proc/kcore.
> >Just don't do that (but I suspect it won't work anyways)
> >
> >If it's not then swiotlb will also not work because it won't get 
> >any memory <4GB.
> >
> >But I doubt this was YH's problem - the panic kernel memory
> >is always reserved and there shouldn't be any ongoing DMAs in this
> >area anyways. And what happens outside the kdump kernel shouldn't matter.
> >
> >I suspect he rather saw problems with non kdump kexec where we
> >can just shut down the GART properly beforehand.
> 
> current I only test kexec only. So clean shut GART in first kernel will 
> help.
> 
> where is hook for shutdown? add one in dma_ops?

I was wondering the same thing. I think it should hook into the
standard device model. It definitely should *not* be in the dma_ops
(it has nothing to do with DMA...) - if needed for this or something
else we should add a struct iommu_ops which includes a dma_ops member.

Cheers,
Muli
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