[SRU][L][PATCH 0/2] Reboot command powers off the system (LP: #2029332)

[Juerg Haefliger]

[Impact]

Issue: When a reboot (or init 6) command is issued the server shuts down instead.

Expected behaviour: To reboot and NOT shutdown

Impacted HW: HPE DL 380 OR Synergy 480 Gen 10 Plus Server 2P core count greater than 16 (like 24,28 or 32)

Impacted OS: Ubuntu 22.04.2 kernel higher than 15.17.15

When the CPU count is 1, issue is not observed. When core count is less than 24 (like 16) issue not observed.

[Fix]

Problem introduced in v5.18 with commit:
08f253ec3767 x86/cpu: Clear SME feature flag when not in use

Fixes for the above:0
9b040453d444 x86/smp: Dont access non-existing CPUID leaf
1f5e7eb7868e x86/smp: Make stop_other_cpus() more robust

[Test Case]

$ sudo reboot
Server should reboot and not power off.

[Where Problems Could Occur]

The fixes modify x86 stop-CPU code so reboot/poweroff of x86 machines could be affected.

Thomas Gleixner (1):
  x86/smp: Make stop_other_cpus() more robust

Tony Battersby (1):
  x86/smp: Dont access non-existing CPUID leaf

 arch/x86/include/asm/cpu.h |  2 ++
 arch/x86/kernel/process.c  | 28 ++++++++++++++---
 arch/x86/kernel/smp.c      | 62 +++++++++++++++++++++++++-------------
 3 files changed, 67 insertions(+), 25 deletions(-)

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2.39.2