[lkml]   [2010]   [Apr]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [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 <> 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.


     \ /
      Last update: 2010-04-04 10:47    [W:0.023 / U:7.536 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site