Date: Fri, 22 Jun 2007 23:54:56 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Yinghai.Lu@Sun.COM
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
       Muli Ben-Yehuda <muli@il.ibm.com>, Andi Kleen <ak@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       Vivek Goyal <vgoyal@in.ibm.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86-64: disable the GART before allocate aperture
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On Fri, 22 Jun 2007 15:43:00 -0700
Yinghai Lu <Yinghai.Lu@Sun.COM> wrote:

> Eric W. Biederman wrote:
> > The original design came from thinking about systems where using the iommu
> > was mandatory.  I think we almost always reserve memory below 1G for the kexec
> > on panic kernel so it really shouldn't be an issue in that case.  Except
> > we need to pass an option to force not using the iommu.  I don't think
> > noiommu or swiotlb is going to make any real difference.
> > 
> > So I'm totally in favor of turning off features if we don't need them and we
> > don't take a tremendous performance hit.  (People get grumpy when writing
> > all of memory to disk takes completely unreasonable amounts of time).
> 
> 
> So you prefer to
> add diable_gart in shutdown or suspend func and let kexec to use swiotlb comand line?

Don't disable it, just don't touch it or any of its mappings. Leave it
*alone*, and use swiotlb. That'll maximise the ability to recover stuff
from the kexec kernel (since for one you may want to dump the gart when a
3d app goes kerblam)

Alan
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