[{"id":3684814,"web_url":"http://patchwork.ozlabs.org/comment/3684814/","msgid":"<65e1b092-146c-4839-89ee-66d2b0589000@linux.ibm.com>","list_archive_url":null,"date":"2026-04-30T15:57:14","subject":"Re: [PATCH] ppc/spapr: Skip system reset for quiesced CPUs","submitter":{"id":86535,"url":"http://patchwork.ozlabs.org/api/people/86535/","name":"Vishal Chourasia","email":"vishalc@linux.ibm.com"},"content":"Hi Anushree, Shivang,\n\nThank you for working on this patch.\n\nOn 30/04/26 14:24, Shivang Upadhyay wrote:\n> During DLPAR CPU hotplug, newly added CPUs start in RTAS stopped state\n> (quiesced). If a kexec crash occurs before the guest starts these CPUs\n> via start-cpu RTAS call, H_SIGNAL_SYS_RESET_ALL_OTHERS will reset them\n> anyway, causing the kdump kernel to hang:\n>\n> [ 5.519483][ T1] Processor 0 is stuck.\n> [ 11.089481][ T1] Processor 1 is stuck.\n>\n> The hypervisor should only reset CPUs that the guest has started. The\n> cpu->env.quiesced flag tracks RTAS stopped state - CPUs in this state\n> are already inactive and should not be reset.\n>\n> Skip system reset for quiesced CPUs to prevent kdump hangs during CPU\n> hotplug operations.\nAlso worth noting that when the system reboots, the newly DLPAR'ed CPUs\nthat were never started via start-cpu will not be present.\n>\n> Cc: Sourabh Jain \n> Cc: Harsh Prateek Bora \n> Cc: Mahesh J Salgaonkar \n> Reported-by: Anushree Mathur \n> Suggested-by: Vishal Chourasia \n> Signed-off-by: Shivang Upadhyay \n> ---\n> hw/ppc/spapr_hcall.c | 4 ++++\n> 1 file changed, 4 insertions(+)\n>\n> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c\n> index 032805a8d0..e63ec24f0c 100644\n> --- a/hw/ppc/spapr_hcall.c\n> +++ b/hw/ppc/spapr_hcall.c\n> @@ -1105,6 +1105,10 @@ static target_ulong h_signal_sys_reset(PowerPCCPU *cpu,\n> continue;\n> }\n> }\n> +\n> + /* Skip quiesced CPUs */\n> + if (c->env.quiesced) continue;\n> +\n> run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL);\n> }\n> return H_SUCCESS;\nReviewed-by: Vishal Chourasia ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=cSfGsxyp;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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