** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Xenial)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1790480

Title:
  random oopses on s390 systems using NVMe devices

Status in Ubuntu on IBM z Systems:
  In Progress
Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Bionic:
  In Progress

Bug description:
  == SRU Justification ==
  IBM is requesting a fix for the following issue found with NVMe devices on 
s390x:

  The trigger is a PCI function whose driver requests more interrupts
  than the architectural maximum. Currently this is only possible with a
  machine that supports 64 CPUs (or more) with a NVMe function attached.
  Note that the LPAR does not have to use >=64 CPUs since the NVMe
  driver uses num_possible_cpus() which is resolved to the machine
  maximum on s390 (since all CPUs are hot-pluggable). The oops happens
  after the driver calls pci_alloc_irq_vectors during device probing -
  so most likely the system will panic during boot.

  The fix has been cc'ed to stable@, but hasn't been picked up for
  Bionic yet.

  == Fix ==
  866f3576a72b s390/pci: fix out of bounds access during irq setup

  == Regression Potential ==
  Low. Affects only s390x systems with more than 64 cpus and NVMe function 
enabled.

  == Test case ==
  Boot the kernel in an affected environment.

  
  === Original bug description ===
  Random oopses on s390 systems using NVMe and running the Ubuntu 18.04.1 
kernel have been reported.
  Bisect of the upstream kernel points to:
  16ccfff28976 nvme: pci: pass max vectors as num_possible_cpus() to 
pci_alloc_irq_vectors

  This commit is correct but reveals a bug in s390s IRQ setup routine. A
  fix is available fixed via:

  Commit-ID : 866f3576a72b2233a76dffb80290f8086dc49e17

  Need also be applied for Ubuntu 18.10

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