Comment 6 for bug 1909286

See the bug lp:1927076 for recent comments/logs/findings. Shortly summarising:
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this issue can be reproduced in the following order:
1. Run the cpu-hotplug test
   sudo ./autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh
2. Run the reuseport_bpf_cpu test
   sudo ./autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/net/reuseport_bpf_cpu
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Seen in logs:
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[ 287.477797] Oops: Exception in kernel mode, sig: 4 [#1]
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Or:
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[ 417.696448] BUG: Unable to handle kernel instruction fetch (NULL pointer?)
[ 417.696522] Faulting instruction address: 0x00000000
[ 417.696677] Oops: Kernel access of bad area, sig: 11 [#1]
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This issue can be reproduced on P8 node entei with:
  * F-5.4 (5.4.0-81-generic)
  * F-5.11 (5.11.0-27-generic #29~20.04.1-Ubuntu)
  * focal-hwe (Linux thiel 5.11.0-27-generic)
  * focal-hwe (5.11.0-34-generic) on thiel
  * H-5.11 (5.11.0-31-generic)
  * Hirsute (5.11.0-31-generic)
  * `gulpin` (8335-GTA) with hirsute (5.11.0-34-generic)
  * `entei` it is also a POWER8 (8335-GTA) with Hirsute latest kernel (5.11.0-34-generic)

Looks like not reproducible on different hardware:
 * Power8 LPAR: P8LPAR05 MAAS
 * Power9: QEMU with 4 or 128 CPUs (and 4 GB of RAM)