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

Joerg Roedel
2010-04-04T10:01:04Z

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.

Joerg