[Bug 1524069] Re: [Xenial] KVM trusty guest 3.13.0-68 raid6-pq panic in raid6_avx21_gen_syndrome() while probing grub devices [was: Xenial KVM: updating Trusty guest from 3.13.0-68 to 3.13.0-71 causes kernel exception]

[Chris J Arges]

Ok I attempted to reproduce without success. What I tried:
- Xenial on Xenial on machine/guest with avx2
- Trusty 3.13.0-{68,71} on Xenial on machine/guest with avx2

In both of these instances I modprobed raid6_pq, in the trusty instance
I triggered an upgrade from 68 to 71 and neither of these caused a
segfault.

The following information would be useful in debugging this:

1) The differences between the guests /proc/cpuinfo with it reproducing and not-reproducing. This can verify the avx2 bit is to blame.
2) Can you simply 'sudo modprobe -r raid6_pq && sudo modprobe raid6_pq' to trigger this issue?
3) Can you test with a xenial guest and a similar configuration to see if this still triggers the issue?
4) If you have the ability testing with different versions of hypervisor (trusty vs xenial) might also be useful.

Thanks,
--chris j arges

** Changed in: linux (Ubuntu)
     Assignee: (unassigned) => Chris J Arges (arges)

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Title:
  [Xenial] KVM trusty guest 3.13.0-68 raid6-pq panic in
  raid6_avx21_gen_syndrome() while probing grub devices [was: Xenial
  KVM: updating Trusty guest from 3.13.0-68 to 3.13.0-71 causes kernel
  exception]

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