linux-kernel - Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash"

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Date:	Tue, 6 Apr 2010 19:51:06 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Chris Wright <chrisw@...s-sol.org>
CC:	Joerg Roedel <joro@...tes.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Bernhard Walle <bernhard@...lle.de>, nhorman@...hat.com,
	nhorman@...driver.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, hbabu@...ibm.com,
	iommu@...ts.linux-foundation.org, vgoyal@...hat.com
Subject: Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash"

On Tue, Apr 06, 2010 at 10:42:57AM -0700, Chris Wright wrote:
> * Joerg Roedel (joro@...tes.org) wrote:
> > On Sun, Apr 04, 2010 at 02:44:36AM -0700, Eric W. Biederman wrote:
> > > Joerg Roedel <joro@...tes.org> writes:
> > > 
> > > > On Sun, Apr 04, 2010 at 09:24:30AM +0200, Bernhard Walle wrote:
> > > >> Am 03.04.10 19:49, schrieb Eric W. Biederman:
> > > >> > Not a problem.  We require a lot of things of the kdump kernel,
> > > >> > and it is immediately apparent in a basic sanity test.
> > > >> 
> > > >> Also, in most cases (for example: distribution kernels), the kdump
> > > >> kernel nowadays is identical to the running kernel. So, if the running
> > > >> kernel has IOMMU support, the kdump kernel also has.
> > > >
> > > > Yes, I know. But is that a requirement for kexec?
> > > 
> > > For normal kexec no.  That path is expected to do a clean hardware
> > > shutdown.
> > > 
> > > For kexec on panic aka kdump the requirement is that your your crash
> > > kernel be able to initialize your hardware from any state it can be
> > > put in.
> > 
> > Ok, if you show me where this is documented for everybody then I am
> > probably convinced :-)
> > We should fixup the gart initialization anyway.
> 
> So, you planning to pull in all 4 patches then?

Yes, I will apply them tomorrow and write a fix for the GART issue this
may introduce.

	Joerg


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