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

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Date:	Sun, 4 Apr 2010 12:01:01 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Bernhard Walle <bernhard@...lle.de>, nhorman@...hat.com,
	nhorman@...driver.com, Joerg Roedel <joerg.roedel@....com>,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Chris Wright <chrisw@...s-sol.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 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.

	Joerg

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