Date: Tue, 6 Apr 2010 19:51:06 +0200
From: Joerg Roedel <joerg.roedel@amd.com>
To: Chris Wright <chrisw@sous-sol.org>
CC: Joerg Roedel <joro@8bytes.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Bernhard Walle <bernhard@bwalle.de>, nhorman@redhat.com,
       nhorman@tuxdriver.com, kexec@lists.infradead.org,
       linux-kernel@vger.kernel.org, hbabu@us.ibm.com,
       iommu@lists.linux-foundation.org, vgoyal@redhat.com
Subject: Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash"
Message-ID: <20100406175106.GH28166@amd.com>
References: <20100403012751.834020949@sous-sol.org>
 <20100403012820.229410717@sous-sol.org>
 <20100403174128.GQ24846@8bytes.org>
 <m1vdc8juju.fsf@fess.ebiederm.org>
 <4BB83EAE.5090609@bwalle.de>
 <20100404085338.GU24846@8bytes.org>
 <m17hond01n.fsf@fess.ebiederm.org>
 <20100404100101.GW24846@8bytes.org>
 <20100406174257.GG29241@sequoia.sous-sol.org>
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On Tue, Apr 06, 2010 at 10:42:57AM -0700, Chris Wright wrote:
> * Joerg Roedel (joro@8bytes.org) wrote:
> > On Sun, Apr 04, 2010 at 02:44:36AM -0700, Eric W. Biederman wrote:
> > > Joerg Roedel <joro@8bytes.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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