Messages in this thread |  | | | Date | Sun, 4 Apr 2010 10:44:36 +0200 | | From | Joerg Roedel <> | | Subject | Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash" |
| |
On Sat, Apr 03, 2010 at 10:44:22AM -0700, Eric W. Biederman wrote: > Joerg Roedel <joro@8bytes.org> writes:
> > Hmm, I think for this we need to change the gart code too and disable > > the gart before its initialization runs to not re-introduce issues fixed > > in commit bc2cea6a34fdb30f118ec75db39a46a191870607, no? > > That is a different code path with a different set of assumptions and > restrictions. On a normal kexec of course we want to do an orderly shutdown.
Thats another problem with this patch. It introduces a difference between the panic-shutdown kexec and the ordinary kexec.
> For the gart with a little luck we can just ignore it on kexec on > panic.
The commit I mentioned above already proves this assumption wrong.
> Unlike a virtualization capable iommu it doesn't prevent access > to devices, when it is enabled. Worst case is that we have to start > including iommu=off for gart systems.
No no no. This is a maintenance nightmare for almost everybody. Where do you want to Document this special cases that 'if kernel uses gart then and only then boot the kexec kernel with iommu=off'. Always passing iommu=off to the kexec kernel doesn't work too for obvious reasons.
> The best case is that we can figure out how to have the gart code > reinitialize itself sanely, starting from some arbitrary point.
Yes, that is missing in this patch. But to keep changes small and don't bother with the gart code at all I suggest to remove the shutdown routine from the amd-iommu code only and not the whole shutdown call in the machine_crash_shutdown path.
Joerg
|  |