Hi Venkat.
On 8/4/26 2:04 PM, Venkat Rao Bagalkote wrote:
Hi,
I'm seeing a boot regression on a Power9 pseries LPAR. The system hangs
very early during boot after:
Quiescing Open Firmware ...
Booting Linux via __start() ...
That is strange. not sure where to look at without any logs.
Is it a specific config that fails or this specific LPAR that fails?
No further kernel output is produced.
Known good:8cd9520d35a6 ("Linux 7.1")
Known bad: 075b74841bd0 ("Linux 7.2-rc6")
Is the kernel built correct at 075b74841bd0 without any errors?
Initial bisect:
A full bisect from v7.1 to v7.2-rc6 converged to:
c5e8e224eb7a
MIPS: RB532: attach the software node to its target GPIO controller
However this commit only modifies:
arch/mips/rb532/devices.c
arch/mips/rb532/gpio.c
and appears unrelated to a Power9/pseries boot hang.
I then narrowed the investigation to the PowerPC pull.
The following commits were tested and boot successfully:
baa590018fbf powerpc: rename arch_irq_disabled_regs
dec63ea6faff powerpc: Prepare to build with generic entry/exit framework
09a9d3a8499d powerpc: introduce arch_enter_from_user_mode
893082ac769b powerpc: Prepare for IRQ entry exit
The following commit reproduces the hang:
334f3f6d7a16 powerpc/entry: Disable interrupts before irqentry_exit
Between the last known good and first known bad points:
893082ac769b powerpc: Prepare for IRQ entry exit
...
bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature
...
334f3f6d7a16 powerpc/entry: Disable interrupts before irqentry_exit
The only substantial architectural/runtime change in this window appears
to be:
bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature
I attempted to test:
bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature
directly, however that commit does not build with my configuration due to:
arch/powerpc/kernel/ptrace/ptrace.c
error: implicit declaration of function 'trace_sys_enter'
error: implicit declaration of function 'trace_sys_exit'
Therefore I could not directly classify bee25f97ad24 as good or bad.
Can you try one commit after this and see if it builds?
i.e "powerpc: Remove unused functions"
Please let me know if there are specific debug patches or boot
parameters you'd like me to test.
Attached is the config file I used.
Regards,
Venkat.
