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Mon, 30 Mar 2026 08:49:54 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 62U8noHP29557366 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 30 Mar 2026 08:49:50 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C63222004B; Mon, 30 Mar 2026 08:49:50 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 425FD20040; Mon, 30 Mar 2026 08:49:48 +0000 (GMT) Received: from [9.123.5.233] (unknown [9.123.5.233]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 30 Mar 2026 08:49:48 +0000 (GMT) Message-ID: <84aa93be-189e-47d9-a159-87bed9f10ee5@linux.ibm.com> Date: Mon, 30 Mar 2026 14:19:47 +0530 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] pseries/kexec: skip resetting CPUs added by firmware but not started by the kernel To: Shivang Upadhyay , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Cc: Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Srikar Dronamraju , "Nysal Jan K.A." , Vishal Chourasia , Ritesh Harjani , Sourabh Jain , Anushree Mathur References: <20260330062206.170437-1-shivangu@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20260330062206.170437-1-shivangu@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: CYuLoeqrbflM1CggovPEVncUO9bctrFt X-Authority-Analysis: v=2.4 cv=frzRpV4f c=1 sm=1 tr=0 ts=69ca3934 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=pGLkceISAAAA:8 a=1UX6Do5GAAAA:8 a=S1_OJBx91vrOljDkdD0A:9 a=QEXdDO2ut3YA:10 a=Et2XPkok5AAZYJIKzHr1:22 X-Proofpoint-ORIG-GUID: SEOYoTI1CUYKE1rh6C6tIXu1US6MiCL0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMwMDA2OCBTYWx0ZWRfX/0rYo0eyDjoS v1fjqPPQvhqnEYUiHFZ5bY4xJ+kj3qGZwA5V4C/dtlTPzH5dD7ddKLRnpCXsL1pwK3iPyYf2+++ GzOSKcC2RAwHpuAFw4gVSHXJVc0RoxVdcCi/jM1kFYU21tcL/aUo9tN9EACw/YMZmrCB1hj5nNe aIUJC9x6isLwe2rwhaTUFDob8dUXS82Wh0maHEoUQ0yAdk901oCudXXwi6GL28BbeqSwj+qPZ2i 0UCBQnq0esbulHpUz5fV6R12696lbwkgCZfTWkZqEgo87Qf8wbJvAfEqzP6jy49v1bbHZ3FBNAd H6G2xAlKlz6wIuo1HjBZUnaUSAMrcv13wltJZ1ogEIBBKeq6R3njBhAEa9XbN94jQ8imQYfn+1y DYP+8JWFw6Yurtk2USRpeJaGp4RSHtV+UOew7cmo4OsEjEivJEs/WnNIphH0YPt65SvfqHDrD60 ytc7GrS0lLrgNLyABDQ== 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=2026-03-29_05,2026-03-28_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 adultscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603300068 Hi Shivang. Few nitpicks. On 3/30/26 11:52 AM, Shivang Upadhyay wrote: > 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. > > 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(); > 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; > > + > +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; Please follow inverted christmas tree for variables. Can the below block be re-written with less indentations? One level indentation removal could be. if (cpu == NMI_IPI_ALL_OTHERS && crash_nmi_ipi) hwcpu = <> else if (cpu == NMI_IPI_ALL_OTHERS) hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS; else > > + 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) { Maybe below to reduce one more indentation level. if ( k == curcpu) continue; > + 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) { It either 1 or 0. So if(paca_ptrs[hwcpu]->cpu_start) is enough. > + 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,