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Tue, 31 Mar 2026 04:34:05 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay07.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 62V4Y0Vh42729924 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Mar 2026 04:34:00 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B34F720043; Tue, 31 Mar 2026 04:34:00 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7D04220040; Tue, 31 Mar 2026 04:33:57 +0000 (GMT) Received: from linux.ibm.com (unknown [9.126.150.29]) by smtpav03.fra02v.mail.ibm.com (Postfix) with SMTP; Tue, 31 Mar 2026 04:33:57 +0000 (GMT) Date: Tue, 31 Mar 2026 10:03:56 +0530 From: Srikar Dronamraju To: Shivang Upadhyay Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Shrikanth Hegde , "Nysal Jan K.A." , Vishal Chourasia , Ritesh Harjani , Sourabh Jain , Anushree Mathur Subject: Re: [PATCH v2] pseries/kexec: skip resetting CPUs added by firmware but not started by the kernel Message-ID: Reply-To: Srikar Dronamraju References: <20260330062206.170437-1-shivangu@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20260330062206.170437-1-shivangu@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=Fdo6BZ+6 c=1 sm=1 tr=0 ts=69cb4ebe cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=8nJEP1OIZ-IA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=pGLkceISAAAA:8 a=1UX6Do5GAAAA:8 a=0W6u05j36Tmt_vxpGP8A:9 a=wPNLvfGTeEIA:10 a=Et2XPkok5AAZYJIKzHr1:22 X-Proofpoint-ORIG-GUID: H3fB2zHjQeAJnwYfVafYmWqBtImBI2Ic X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMxMDAzOCBTYWx0ZWRfX9PbvKKeArHtp 2yexzw7UABbg+1hOhyZxVRjbpgK83XN0IwiBzPki/vA8dY4zXii6Btvyifr2O2SQM+VtmcdAtWn nJ56ni1c853k9kWQmkSncwG/HRfQ/TyX0Www83JUz8/4oJkvbfzrkBYDEsT4GOAqBwh1KdwGsvC U3oKivFPujE9J+afNew8Ae0EEKeHSLowsqOZxhAPw8H6YkatWfvpSAJdxxXqxLasluFLun4Te7Z TWZIlkMib0jwTVLq36Cqgv+/Qrn3BbPisCYP/Op9AiKirkxEP5ufI+Cow5AS+MVzRqp+gtSe+38 y/IlRA+O3Eqv4V10sh6aTQwQsrkFlHWmX4fc6sEoOYx1Wb4r221juMduT2IjyYu6oZtpL0HaykW z3x1hkAQiEcceehYPH/jeE8a+vy4+ZeJUpqDj8dL8IzRaUwHmFiK7SEI/ciVaSPmw/zNad9P+GY Y4ighTvC21xvQx6J54Q== X-Proofpoint-GUID: Rve6B8CFscjZxprw9FxntOv9_st3M5yG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-31_01,2026-03-28_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1011 bulkscore=0 suspectscore=0 priorityscore=1501 adultscore=0 malwarescore=0 phishscore=0 spamscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603310038 * Shivang Upadhyay [2026-03-30 11:52:06]: > During DLPAR operations, the newly added CPUs start in halted mode. > The kernel then takes some time to initialize those CPUs internally and > start them using the "start-cpu" RTAS call. However, if a kexec crash > occurs in this window (before the new CPU has been initialized), > the kexec NMI will try to reset all other CPUs from the crashing CPU. > This leads to firmware starting the uninitialized CPUs as well. What would happen if an non kexec crash nmi was delivered when we did a DLPAR operation and before the CPUs are initialized? > > This can cause the kdump kernel to hang during bring-up. > > Sample Log: > [175993.028231][ T1502] NIP [00007fffb953f394] 0x7fffb953f394 > [175993.028314][ T1502] LR [00007fffb953f394] 0x7fffb953f394 > [175993.028390][ T1502] --- interrupt: 3000 > [ 5.519483][ T1] Processor 0 is stuck. > [ 11.089481][ T1] Processor 1 is stuck. > > To fix this, only issue the system-reset hcall to CPUs that have > actually been started by the kernel. > > Cc: Madhavan Srinivasan > Cc: Michael Ellerman > Cc: Nicholas Piggin > Cc: Christophe Leroy > Cc: Srikar Dronamraju > Cc: Shrikanth Hegde > Cc: Nysal Jan K.A. > Cc: Vishal Chourasia > Cc: Ritesh Harjani > Cc: Sourabh Jain > Reported-by: Anushree Mathur > Signed-off-by: Shivang Upadhyay > --- > Changelog: > > V2: > * added set_crash_nmi_ipi to saperate crash's case from other nmi_ipi > users > > V1: > * https://lore.kernel.org/all/20251205142825.44698-1-shivangu@linux.ibm.com/ > --- > arch/powerpc/include/asm/smp.h | 1 + > arch/powerpc/kernel/smp.c | 1 + > arch/powerpc/platforms/pseries/smp.c | 29 +++++++++++++++++++++++++++- > 3 files changed, 30 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h > index e41b9ea42122..cb74201f5674 100644 > --- a/arch/powerpc/include/asm/smp.h > +++ b/arch/powerpc/include/asm/smp.h > @@ -47,6 +47,7 @@ struct smp_ops_t { > void (*cause_ipi)(int cpu); > #endif > int (*cause_nmi_ipi)(int cpu); > + void (*set_crash_nmi_ipi)(void); > void (*probe)(void); > int (*kick_cpu)(int nr); > int (*prepare_cpu)(int nr); > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c > index 3467f86fd78f..3390ee8adf79 100644 > --- a/arch/powerpc/kernel/smp.c > +++ b/arch/powerpc/kernel/smp.c > @@ -594,6 +594,7 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *)) > { > int cpu; > > + smp_ops->set_crash_nmi_ipi(); Shouldn't we be checking got smp_ops->set_crash_nmi_ipi being non-NULL before calling. Dont we expect set_crash_nmi_ipi() to be NULL in PowerNV after this patch? Or what would happen if set_crash_nmi_ipi() was called in PowerNV code? > smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, crash_ipi_callback, 1000000); > if (kdump_in_progress() && crash_wake_offline) { > for_each_present_cpu(cpu) { > diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c > index db99725e752b..c6c2baacca9a 100644 > --- a/arch/powerpc/platforms/pseries/smp.c > +++ b/arch/powerpc/platforms/pseries/smp.c > @@ -51,6 +51,9 @@ > */ > static cpumask_var_t of_spin_mask; > > + Nit: Are we adding an unnecessary newline? > +static int crash_nmi_ipi; > + > /* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */ > int smp_query_cpu_stopped(unsigned int pcpu) > { > @@ -171,12 +174,35 @@ static void dbell_or_ic_cause_ipi(int cpu) > ic_cause_ipi(cpu); > } > > +static void pseries_set_crash_nmi_ipi(void) > +{ > + crash_nmi_ipi = 1; > +} > + > static int pseries_cause_nmi_ipi(int cpu) > { > int hwcpu; > + int k, curcpu; > > + curcpu = smp_processor_id(); > if (cpu == NMI_IPI_ALL_OTHERS) { > - hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS; > + if (crash_nmi_ipi) { > + for_each_present_cpu(k) { > + if (k != curcpu) { > + hwcpu = get_hard_smp_processor_id(k); > + > + /* it is possible that cpu is present, > + * but not started yet. > + */ > + > + if (paca_ptrs[hwcpu]->cpu_start == 1) { > + plpar_signal_sys_reset(hwcpu); > + } > + } > + } > + return 1; > + } else > + hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS; > } else { > if (cpu < 0) { > WARN_ONCE(true, "incorrect cpu parameter %d", cpu); > @@ -243,6 +269,7 @@ static struct smp_ops_t pseries_smp_ops = { > .message_pass = NULL, /* Use smp_muxed_ipi_message_pass */ > .cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */ > .cause_nmi_ipi = pseries_cause_nmi_ipi, > + .set_crash_nmi_ipi = pseries_set_crash_nmi_ipi, > .probe = pSeries_smp_probe, > .prepare_cpu = pseries_smp_prepare_cpu, > .kick_cpu = smp_pSeries_kick_cpu, > -- > 2.53.0 > -- Thanks and Regards Srikar Dronamraju