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[Thadeu Lima de Souza Cascardo <1736954@xxxxxxxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu Bionic)
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1736954

Title:
  ppc64el: Do not call ibm,os-term on panic

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed
Status in linux source package in Artful:
  Fix Committed
Status in linux source package in Bionic:
  Fix Released

Bug description:
  [Impact]
  When panic_timeout is set, the user would expect the system to reboot. However, it is shutdown, possibly requiring user intervention to power on the system again. This may impact availability. This happens under certain versions of qemu (2.10+) emulating pseries.

  [Test Case]
  Built kernels (trusty, xenial, zesty, artful) have been tested and they reboot after the fix, when running under an affected qemu.

  [Regression Potential]
  fadump might require that RTAS ibm,os-term be called. The fix should still allow it to be called when fadump is registered.

  
  -----------

  When panic_timeout is set, the user would expect that the system would
  reboot after some timeout after a panic.

  However, on powerpc architecture, a panic notifier may not ever return
  and even shutdown the system. The main example that impacts platforms
  we support is pseries calling RTAS ibm,os-term.

  That panic notifier and calling RTAS ibm,os-term is useful for fadump,
  so this should not be impacted.

  The Linux code has changed back and forth on considering the
  panic_timeout setting and checking whether ibm,extended-os-term was
  available. Unfortunately, recent changes on qemu led to the guest
  being shut down when calling ibm,os-term even when ibm,extended-os-
  term was available.

  Luckily, upstream Linux already has the change that does not call ibm
  ,os-term on panic, but only during fadump. So, we can use that commit
  for fixing this. Changing qemu itself is harder as: 1) qemu community
  already decided some qemu settings should override PAPR; 2) updating
  deployed hypervisor is harder than updating our guest kernels.

  Cascardo.

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