[Bug 1809701] [NEW] cpu_hot_plug test in ubuntu_kernel_selftest failed on Moonshot ARM64

Public bug reported:

Test failed with "Operation not supported" when trying to offline a CPU:
echo 0 > $SYSFS/devices/system/cpu/cpu$1/online

This issue cannot be reproduced on CaviumThunderX ARM64 server, just the
moonshots.

$ sudo make -C linux/tools/testing/selftests TARGETS=cpu-hotplug run_tests
make: Entering directory '/home/ubuntu/linux/tools/testing/selftests'
make[1]: Entering directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make[1]: Entering directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
TAP version 13
selftests: cpu-hotplug: cpu-on-off-test.sh
========================================
pid 8132's current affinity mask: ff
pid 8132's new affinity mask: 1
CPU online/offline summary:
Cpus in online state: 0-7
Cpus in offline state: 0
Limited scope test: one hotplug cpu
(leaves cpu in the original state):
online to offline to online: cpu 7
./cpu-on-off-test.sh: line 92: echo: write error: Operation not supported
offline_cpu_expect_success 7: unexpected fail
not ok 1..1 selftests: cpu-hotplug: cpu-on-off-test.sh [FAIL]
make[1]: Leaving directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make: Leaving directory '/home/ubuntu/linux/tools/testing/selftests'

The CPU hotplug config was enabled on this SUT:
$ cat /boot/config-`uname -r` | grep HOTPLUG | grep CPU
CONFIG_HOTPLUG_CPU=y
CONFIG_ACPI_HOTPLUG_CPU=y
# CONFIG_CPU_HOTPLUG_STATE_CONTROL is not set

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: linux-image-4.18.0-13-generic 4.18.0-13.14
ProcVersionSignature: User Name 4.18.0-13.14-generic 4.18.17
Uname: Linux 4.18.0-13-generic aarch64
AlsaDevices:
total 0
crw-rw---- 1 root audio 116, 1 Dec 25 04:01 seq
crw-rw---- 1 root audio 116, 33 Dec 25 04:01 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.10-0ubuntu13.1
Architecture: arm64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Tue Dec 25 04:54:54 2018
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1:
PciMultimedia:

ProcFB:

ProcKernelCmdLine: console=ttyS0,9600n8r ro
RelatedPackageVersions:
linux-restricted-modules-4.18.0-13-generic N/A
linux-backports-modules-4.18.0-13-generic N/A
linux-firmware 1.175.1
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: ubuntu-kernel-tests
Importance: Undecided
Status: New

** Affects: linux (Ubuntu)
Importance: Undecided
Status: New


** Tags: apport-bug arm64 cosmic uec-images

** Also affects: ubuntu-kernel-tests
Importance: Undecided
Status: New

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https://bugs.launchpad.net/bugs/1809701

Title:
cpu_hot_plug test in ubuntu_kernel_selftest failed on Moonshot ARM64

Status in ubuntu-kernel-tests:
New
Status in linux package in Ubuntu:
New

Bug description:
Test failed with "Operation not supported" when trying to offline a CPU:
echo 0 > $SYSFS/devices/system/cpu/cpu$1/online

This issue cannot be reproduced on CaviumThunderX ARM64 server, just
the moonshots.

$ sudo make -C linux/tools/testing/selftests TARGETS=cpu-hotplug run_tests
make: Entering directory '/home/ubuntu/linux/tools/testing/selftests'
make[1]: Entering directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make[1]: Entering directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
TAP version 13
selftests: cpu-hotplug: cpu-on-off-test.sh
========================================
pid 8132's current affinity mask: ff
pid 8132's new affinity mask: 1
CPU online/offline summary:
Cpus in online state: 0-7
Cpus in offline state: 0
Limited scope test: one hotplug cpu
(leaves cpu in the original state):
online to offline to online: cpu 7
./cpu-on-off-test.sh: line 92: echo: write error: Operation not supported
offline_cpu_expect_success 7: unexpected fail
not ok 1..1 selftests: cpu-hotplug: cpu-on-off-test.sh [FAIL]
make[1]: Leaving directory '/home/ubuntu/linux/tools/testing/selftests/cpu-hotplug'
make: Leaving directory '/home/ubuntu/linux/tools/testing/selftests'

The CPU hotplug config was enabled on this SUT:
$ cat /boot/config-`uname -r` | grep HOTPLUG | grep CPU
CONFIG_HOTPLUG_CPU=y
CONFIG_ACPI_HOTPLUG_CPU=y
# CONFIG_CPU_HOTPLUG_STATE_CONTROL is not set

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: linux-image-4.18.0-13-generic 4.18.0-13.14
ProcVersionSignature: User Name 4.18.0-13.14-generic 4.18.17
Uname: Linux 4.18.0-13-generic aarch64
AlsaDevices:
total 0
crw-rw---- 1 root audio 116, 1 Dec 25 04:01 seq
crw-rw---- 1 root audio 116, 33 Dec 25 04:01 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.10-0ubuntu13.1
Architecture: arm64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Tue Dec 25 04:54:54 2018
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1:
PciMultimedia:

ProcFB:

ProcKernelCmdLine: console=ttyS0,9600n8r ro
RelatedPackageVersions:
linux-restricted-modules-4.18.0-13-generic N/A
linux-backports-modules-4.18.0-13-generic N/A
linux-firmware 1.175.1
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)

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