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[Launchpad Bug Tracker <1988527@xxxxxxxxxxxxxxxxxx>]

You have been subscribed to a public bug by Paride Legovini (paride):

[ 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.

[ 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

** Affects: autopkgtest (Ubuntu)
     Importance: High
     Assignee: Paride Legovini (paride)
         Status: Fix Released

** Affects: autopkgtest (Ubuntu Jammy)
     Importance: High
     Assignee: Paride Legovini (paride)
         Status: In Progress

** Affects: autopkgtest (Debian)
     Importance: Unknown
         Status: Fix Committed


** Tags: ppc64el
-- 
autopkgtest_qemu doesn't use accel=kvm on ppc64le, being fully unusable on that arch
https://bugs.launchpad.net/bugs/1988527
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