group.of.nepali.translators team mailing list archive

[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

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

** Also affects: linux (Ubuntu Cosmic)
   Importance: High
     Assignee: Guilherme G. Piccoli (gpiccoli)
       Status: Confirmed

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

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

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https://bugs.launchpad.net/bugs/1797990

Title:
  kdump fail due to an IRQ storm

Status in linux package in Ubuntu:
  Confirmed
Status in linux source package in Trusty:
  New
Status in linux source package in Xenial:
  New
Status in linux source package in Bionic:
  New
Status in linux source package in Cosmic:
  Confirmed

Bug description:
  We have reports of a kdump failure in Ubuntu (in x86 machine) that was
  narrowed down to a MSI irq storm coming from a PCI network device.

  The bug manifests as a lack of progress in the boot process of the
  kdump kernel, and a storm of kernel messages like:

  [...]
  [  342.265294] do_IRQ: 0.155 No irq handler for vector
  [  342.266916] do_IRQ: 0.155 No irq handler for vector
  [  347.258422] do_IRQ: 14053260 callbacks suppressed
  [...]

  The root cause of the the issue is that the kdump kernel kexec process
  does not ensure PCI devices are reset and/or MSI capabilities are
  disabled, so a PCI device could produce a huge amount of PCI irqs
  which would take all the processing time for the CPU (specially since
  we restrict the kdump kernel to use one single CPU only).

  This was tested using upstream kernel version 4.18, and the problem reproduces.
  In the specific test scenario, the PCI NIC was an "Intel 82599ES 10-Gigabit [8086:10fb]" that was used in SR-IOV PCI passthrough mode (vfio_pci), under high load on the guest.

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