canonical-ubuntu-qa team mailing list archive

[Launchpad Bug Tracker <1988527@xxxxxxxxxxxxxxxxxx>]

** Merge proposal linked:
   https://code.launchpad.net/~paride/ubuntu/+source/autopkgtest/+git/autopkgtest/+merge/429974

-- 
You received this bug notification because you are a member of
Canonical's Ubuntu QA, which is subscribed to the bug report.
https://bugs.launchpad.net/bugs/1988527

Title:
  autopkgtest_qemu doesn't use accel=kvm on ppc64le, being fully
  unusable on that arch

Status in autopkgtest package in Ubuntu:
  Fix Released
Status in autopkgtest source package in Jammy:
  In Progress
Status in autopkgtest package in Debian:
  Fix Committed

Bug description:
  [ Impact ]

  On Power9 the qemu based autopkgtest commands create VMs that are
  extremely slow and fail with obscure errors (partially discussed in
  LP: #1973628, comment 8). This can be reproduced for example by
  running:

    autopkgtest-buildvm-ubuntu-cloud -v -r jammy --ram-size 1024

  but autopkgtest-virt-qemu is also affected.

  This happens because autopkgtest fails to detect the system
  architecture as KVM capable due to a typo in the architecture name
  (ppc64el instead of ppc64le). This upload fixes the typo.

  Fixing this bug in Jammy will allow users and developers to manually
  run autopkgtests on ppc64el. This is useful for example in +1
  maintenance.

  [ Test Plan ]

  Run:

    autopkgtest-buildvm-ubuntu-cloud -v -r jammy --ram-size 1024

  on an affected system.

  Buggy package => the command takes hours to complete and prints lots
  of obscure errors.

  Fixed package => the command completes in minutes.

  [ Where problems could occur ]

  Without this fix qemu based autopkgtest could in principle complete
  even when KVM is available (/dev/kvm exists) but broken, as it may be
  in some nested virtualization scenarios. This said, without KVM qemu
  based appears to be very broken due to timeouts caused by its extreme
  slowness, so I think the risk of causing a regression is marginal.

  [ Other Info ]

  The very same fix has been submitted and merged upstream, and released
  to Kinetic via a clean cherry-pick.

  [ Original Description ]

  On Power9 the qemu based autopkgtest commands create VMs that are
  extremely slow and fail with obscure errors (partially discussed in
  LP: #1973628, comment 8). This can be reproduced for example by
  running:

    autopkgtest-buildvm-ubuntu-cloud -v -r jammy --ram-size 1024

  but autopkgtest-virt-qemu is also affected. The extreme slowness of
  the VMs made me think that something was off with the virtualization
  settings. I modified autopkgtest_qemu.py so that qemu-system-ppc64le
  is called with '-machine accel=kvm' (which I think is the same as
  '-machine pseries,accel=kvm' with pseries being the default machine
  type).

  With this change everything is very fast and reliable. These warnings
  also went away:

  qemu-system-ppc64le: warning: TCG doesn't support requested feature, cap-cfpc=workaround
  qemu-system-ppc64le: warning: TCG doesn't support requested feature, cap-sbbc=workaround
  qemu-system-ppc64le: warning: TCG doesn't support requested feature, cap-ibs=workaround
  qemu-system-ppc64le: warning: TCG doesn't support requested feature, cap-ccf-assist=on

  indicating that we were using TCG emulation before.

  I imagine that Qemu has good reasons not to default to accel=kvm or
  accel=kvm:tcg on ppc64, but think it's reasonable to assume it's
  available and enable it in autopkgtest.

  We can fix this in autopkgtest upstream, but it would be nice to
  verify if this is an issue with Debian too before submitting a salsa
  MR.

  [1] https://wiki.qemu.org/Documentation/TCG

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/autopkgtest/+bug/1988527/+subscriptions