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  1. RHEL
  2. RHEL-11812

[s390x]VM unexpectedly runs with invalid cpuset definition

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      Description of problem:
      A machine with an invalid CPU set - out of the range of available host cpus - starts successfully but is expected to fail. This seemingly happens inconsistently on a specific host with a specific number of CPUs and doesn't reproduce on other archs or s390x hosts where two different error messages are displayed and the machines wouldn't start (as expected).

      Version-Release number of selected component (if applicable):
      libvirt-8.9.0-2.el9.s390x
      kernel-5.14.0-197.el9.s390x

      How reproducible:
      100% on specific s390x host

      Steps to Reproduce:
      1. On a host with 12 CPUs (value "CPU(s)" from lscpu|grep CPU), define a domain with cpu set out of range, e.g.
      <vcpu cpuset="0-12,^2" current="3" placement="static">8</vcpu>
      or equivalently
      <vcpu cpuset="0-1,3-12" current="3" placement="static">8</vcpu>

      2. Try to start the vm

      Actual results:
      The VM starts successfully

      Expected results:
      The VM doesn't start, instead there's an error message from cgroups "Numerical result out of range"

      Additional info:
      A) Yingshun confirmed the expected result on x86_64.

      B) In the reported case we see cgroup values

      1. cat /sys/fs/cgroup/machine.slice/machine-qemu\\x2d1\\x2davocado\\x2dvt
        x2dvm1.scope/libvirt/emulator/cpuset.cpus
        0-1,3-12
      2. cat /sys/fs/cgroup/machine.slice/machine-qemu\\x2d1\\x2davocado\\x2dvt
        x2dvm1.scope/libvirt/emulator/cpuset.cpus.effective
        0-1,3-11

      C) On another s390x host with 4 CPUs and the same component versions, this can't be reproduced, instead another error message is showing. With
      <vcpu placement='static' cpuset='0-4,^2' current='3'>4</vcpu>
      we get an error message
      error: Invalid value '0-1,3-4' for 'cpuset.cpus': Invalid argument

      Auto case is vcpu_affinity.negative_test.vcpu.outrange_cpuset

              smitterl@redhat.com Sebastian Mitterle
              smitterl@redhat.com Sebastian Mitterle
              virt-maint virt-maint
              Sebastian Mitterle Sebastian Mitterle
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                Created:
                Updated:
                Resolved: