On 30/04/26 2:24 pm, Shivang Upadhyay wrote:
During DLPAR CPU hotplug, newly added CPUs start in RTAS stopped state
(quiesced). If a kexec crash occurs before the guest starts these CPUs
via start-cpu RTAS call, H_SIGNAL_SYS_RESET_ALL_OTHERS will reset them
anyway, causing the kdump kernel to hang:
[ 5.519483][ T1] Processor 0 is stuck.
[ 11.089481][ T1] Processor 1 is stuck.
The hypervisor should only reset CPUs that the guest has started. The
cpu->env.quiesced flag tracks RTAS stopped state - CPUs in this state
are already inactive and should not be reset.
Skip system reset for quiesced CPUs to prevent kdump hangs during CPU
hotplug operations.
Cc: Sourabh Jain <[email protected]>
Cc: Harsh Prateek Bora <[email protected]>
Cc: Mahesh J Salgaonkar <[email protected]>
Reported-by: Anushree Mathur <[email protected]>
Suggested-by: Vishal Chourasia <[email protected]>
Signed-off-by: Shivang Upadhyay <[email protected]>
---
hw/ppc/spapr_hcall.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 032805a8d0..e63ec24f0c 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1105,6 +1105,10 @@ static target_ulong h_signal_sys_reset(PowerPCCPU *cpu,
continue;
}
}
+
+ /* Skip quiesced CPUs */
+ if (c->env.quiesced) continue;
Qemu coding style suggests having braces even for single statements
within an if block.
Please refer Block structure in docs/devel/style.rst.
+
run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL);
}
return H_SUCCESS;
