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envelope-from=harshpb@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Shivang Upadhyay 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 Cc: Harsh Prateek Bora Cc: Mahesh J Salgaonkar Reported-by: Anushree Mathur Suggested-by: Vishal Chourasia Reviewed-by: Vishal Chourasia Signed-off-by: Shivang Upadhyay Link: https://lore.kernel.org/qemu-devel/20260511095055.82495-1-shivangu@linux.ibm.com [harshpb: expanded comment to elobarate more on the rationale] Signed-off-by: Harsh Prateek Bora --- hw/ppc/spapr_hcall.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c index 032805a8d0..60ba215e86 100644 --- a/hw/ppc/spapr_hcall.c +++ b/hw/ppc/spapr_hcall.c @@ -1105,6 +1105,15 @@ static target_ulong h_signal_sys_reset(PowerPCCPU *cpu, continue; } } + + /* Skip quiesced CPUs - they are in RTAS stopped state and + * should not be reset. This prevents kdump hangs when CPUs + * are hotplugged but not yet started by the guest. + */ + if (c->env.quiesced) { + continue; + } + run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL); } return H_SUCCESS; -- 2.52.0