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GET /api/patches/2196952/?format=api
{ "id": 2196952, "url": "http://patchwork.ozlabs.org/api/patches/2196952/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260216171456.527608-2-vishalc@linux.ibm.com/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/", "list_archive_url_format": "https://lore.kernel.org/linuxppc-dev/{}/", "commit_url_format": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id={}" }, "msgid": "<20260216171456.527608-2-vishalc@linux.ibm.com>", "list_archive_url": "https://lore.kernel.org/linuxppc-dev/20260216171456.527608-2-vishalc@linux.ibm.com/", "date": "2026-02-16T17:14:57", "name": "[RFC,v1] kexec: optimize crash hotplug by filtering redundant FDT updates", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "961c68d154bb1dd950e463f105baea2c52d42463", "submitter": { "id": 86535, "url": "http://patchwork.ozlabs.org/api/people/86535/?format=api", "name": "Vishal Chourasia", "email": "vishalc@linux.ibm.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260216171456.527608-2-vishalc@linux.ibm.com/mbox/", "series": [ { "id": 492333, "url": "http://patchwork.ozlabs.org/api/series/492333/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=492333", "date": "2026-02-16T17:14:57", "name": "[RFC,v1] kexec: optimize crash hotplug by filtering redundant FDT updates", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/492333/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2196952/comments/", "check": "success", "checks": "http://patchwork.ozlabs.org/api/patches/2196952/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linuxppc-dev+bounces-16886-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linuxppc-dev@lists.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=rYRiFaSy;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.ibm.com;\n dkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=rYRiFaSy; dkim-atps=neutral;\n spf=pass (client-ip=148.163.158.5; helo=mx0b-001b2d01.pphosted.com;\n envelope-from=vishalc@linux.ibm.com;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.ibm.com", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc\n\t:content-transfer-encoding:date:from:message-id:mime-version\n\t:subject:to; s=pp1; bh=DlfQBWh/1ejwW858oNbtS1e0RO+K3ejkv0QSbNUrw\n\t9w=; b=rYRiFaSy5WobzD9BZF/g43fnh5iBrOrUJPV3qdgAucJ3ilR2n9DzNptQW\n\t6lzmDmsiPjLAKX/S43ptirBArALrLJN9bNzM2CFkfb5Cxy/0Waax64tqRYwTBQuD\n\tkt9wYPM4FyE6kK+LP6zCWIYTQRgbA9Vfr5lUKyGWYIBrsxm3OAm5mcT16OXX+HOy\n\t2MIV0elxRAHi3VsuNrSdOkLS5/Yb+8wyM3mg1d3eJdoGGRAg6H4Fmcu9KZT7PUC4\n\tPsomsJy7yMGXgGWsanGkmh9b0fgEQgQtq2BmUN/+9oNBKoTblbeUVy2ALLzMf6wZ\n\t7aZ4XfE19l66pc94PnE5R5Mi51N8Q==", "From": "Vishal Chourasia <vishalc@linux.ibm.com>", "To": "maddy@linux.ibm.com, sourabhjain@linux.ibm.com,\n linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,\n kexec@lists.infradead.org", "Cc": "mpe@ellerman.id.au, tglx@kernel.org, mingo@redhat.com, bp@alien8.de,\n dave.hansen@linux.intel.com, x86@kernel.org,\n akpm@linux-foundation.org,\n bhe@redhat.com, mahesh@linux.ibm.com, ritesh.list@gmail.com,\n vishalc@linux.ibm.com, thuth@redhat.com, hbathini@linux.ibm.com,\n eajames@linux.ibm.com, dwmw@amazon.co.uk, kai.huang@intel.com,\n pbonzini@redhat.com, ubizjak@gmail.com, coxu@redhat.com,\n fuqiang.wang@easystack.cn, brgerst@gmail.com, liaoyuanhong@vivo.com,\n jbohac@suse.cz", "Subject": "[RFC PATCH v1] kexec: optimize crash hotplug by filtering redundant\n FDT updates", "Date": "Mon, 16 Feb 2026 22:44:57 +0530", "Message-ID": "<20260216171456.527608-2-vishalc@linux.ibm.com>", "X-Mailer": "git-send-email 2.53.0", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-TM-AS-GCONF": "00", "X-Proofpoint-Reinject": "loops=2 maxloops=12", "X-Proofpoint-ORIG-GUID": "nCI5gqZepZ3KLvK25N5CfSurnFU4yjHE", "X-Authority-Analysis": "v=2.4 cv=Md9hep/f c=1 sm=1 tr=0 ts=6993518a cx=c_pps\n a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17\n a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22\n a=GgsMoib0sEa3-_RKJdDe:22 a=VnNF1IyMAAAA:8 a=Q1TS8951KDF7Hiku8JMA:9", "X-Proofpoint-Spam-Details-Enc": "AW1haW4tMjYwMjE2MDE0NyBTYWx0ZWRfX6Rg7r6oBnCeZ\n Yhuz0zIh4QajyIwnpEk/Dw7aiouITOnmhtHtqgVe1bt1eFkj7UznntfwwPfwHFgJjjobZaDWZlZ\n fNUhINMAMKVxnhppXwANur3mCQ8LblLVNT4w4K4H3lQ56zxNdb/LBg01JwRfp/ujgKL8pAROAuU\n kD69SH1BrGHrvZDZSx3D1s8tlsnMBJdmH+Asio7YqMn6vE20ynZcs4wgdgxkynMWTMnRvHETfYF\n 2hpnFhgBHZS2kPtRPkhROw0USndL7dMnHg0+cprouXi8M9oYzmxQzYBJ6kN3QvblKCg/YHTF88r\n IoGg9JekEROzYF1fqcF/U7lu2psgCXjkwGbwcECia64/BDutp2zhCKGcnYI+y6oAILLM3aTVVom\n w25wdMTlxH3BlLNZCgG0Ln/LZmkWdxDlz6Y3f2Un+o4WF8hJ5IjIFMefTjZgeZXzNaZSDmsnHqA\n i/FFS5qPkjr8iftQaUw==", "X-Proofpoint-GUID": "PrsvvTrYUNbwbokUKjJ5M4S3gZk1CWkf", "X-Proofpoint-Virus-Version": "vendor=baseguard\n engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49\n definitions=2026-02-16_05,2026-02-16_03,2025-10-01_01", "X-Proofpoint-Spam-Details": "rule=outbound_notspam policy=outbound score=0\n clxscore=1011 impostorscore=0 lowpriorityscore=0 spamscore=0 adultscore=0\n priorityscore=1501 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0\n classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0\n reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602160147", "X-Spam-Status": "No, score=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tLOTS_OF_MONEY,RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,\n\tSPF_HELO_NONE,SPF_PASS autolearn=disabled version=4.0.1 OzLabs 8", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "The arch_crash_handle_hotplug_event() interface currently lacks the CPU\nindex associated with hotplug events. This forces architecture handlers,\nspecifically on PowerPC, to unconditionally update the crash Flattened\nDevice Tree (FDT) for every CPU online event which should only be done\nin case of DLPAR operations which add/remove new device tree node under the\n/cpus. On large systems with crash kernel loaded, this behavior causes a\nsignificant performance bottleneck. For example, during SMT switch\noperations involving 1400 CPUs, the redundant execution of\nupdate_crash_fdt() adds over half an hour of overhead\n\nAs shown in the ftrace function graph:\n 83) bash-14351 | $ 2283891 us | } /* update_cpus_node */\n\nThis patch passes the CPU index to the arch-specific handlers and\nmodifies the PowerPC implementation to check cpus_booted_once_mask. If\na CPU has been previously initialized, its FDT node is already present,\nallowing the handler to skip the redundant update_crash_fdt() call.\n\nFixes: b741092d5976 (\"powerpc/crash: add crash CPU hotplug support\")\nSigned-off-by: Vishal Chourasia <vishalc@linux.ibm.com>\n---\n arch/powerpc/include/asm/kexec.h | 2 +-\n arch/powerpc/kexec/crash.c | 5 +++--\n arch/x86/include/asm/kexec.h | 2 +-\n arch/x86/kernel/crash.c | 2 +-\n include/linux/crash_core.h | 2 +-\n kernel/crash_core.c | 2 +-\n 6 files changed, 8 insertions(+), 7 deletions(-)", "diff": "diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h\nindex bd4a6c42a5f3..2d6d32942bc0 100644\n--- a/arch/powerpc/include/asm/kexec.h\n+++ b/arch/powerpc/include/asm/kexec.h\n@@ -137,7 +137,7 @@ static inline void crash_setup_regs(struct pt_regs *newregs,\n }\n \n #ifdef CONFIG_CRASH_HOTPLUG\n-void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);\n+void arch_crash_handle_hotplug_event(struct kimage *image, int cpu, void *arg);\n #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event\n \n int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags);\ndiff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c\nindex a325c1c02f96..d280883c8ab6 100644\n--- a/arch/powerpc/kexec/crash.c\n+++ b/arch/powerpc/kexec/crash.c\n@@ -568,7 +568,7 @@ int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)\n *\t part of the FDT.\n * Memory add/remove: No action is taken as this is not yet supported.\n */\n-void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)\n+void arch_crash_handle_hotplug_event(struct kimage *image, int cpu, void *arg)\n {\n \tstruct memory_notify *mn;\n \n@@ -577,7 +577,8 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)\n \t\treturn;\n \n \tcase KEXEC_CRASH_HP_ADD_CPU:\n-\t\tupdate_crash_fdt(image);\n+\t\tif (!cpumask_test_cpu(cpu, &cpus_booted_once_mask))\n+\t\t\tupdate_crash_fdt(image);\n \t\tbreak;\n \n \tcase KEXEC_CRASH_HP_REMOVE_MEMORY:\ndiff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h\nindex 5cfb27f26583..57f5c5067267 100644\n--- a/arch/x86/include/asm/kexec.h\n+++ b/arch/x86/include/asm/kexec.h\n@@ -222,7 +222,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);\n extern void kdump_nmi_shootdown_cpus(void);\n \n #ifdef CONFIG_CRASH_HOTPLUG\n-void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);\n+void arch_crash_handle_hotplug_event(struct kimage *image, int cpu, void *arg);\n #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event\n \n int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags);\ndiff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c\nindex 335fd2ee9766..dda4ad1a163e 100644\n--- a/arch/x86/kernel/crash.c\n+++ b/arch/x86/kernel/crash.c\n@@ -508,7 +508,7 @@ unsigned int arch_crash_get_elfcorehdr_size(void)\n *\n * Prepare the new elfcorehdr and replace the existing elfcorehdr.\n */\n-void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)\n+void arch_crash_handle_hotplug_event(struct kimage *image, int cpu, void *arg)\n {\n \tvoid *elfbuf = NULL, *old_elfcorehdr;\n \tunsigned long nr_mem_ranges;\ndiff --git a/include/linux/crash_core.h b/include/linux/crash_core.h\nindex d35726d6a415..118e2e03e0b5 100644\n--- a/include/linux/crash_core.h\n+++ b/include/linux/crash_core.h\n@@ -42,7 +42,7 @@ static inline int crash_load_dm_crypt_keys(struct kimage *image) {return 0; }\n #endif\n \n #ifndef arch_crash_handle_hotplug_event\n-static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }\n+static inline void arch_crash_handle_hotplug_event(struct kimage *image, int cpu, void *arg) { }\n #endif\n \n int crash_check_hotplug_support(void);\ndiff --git a/kernel/crash_core.c b/kernel/crash_core.c\nindex 3952b3e102e0..27c6f57e5169 100644\n--- a/kernel/crash_core.c\n+++ b/kernel/crash_core.c\n@@ -634,7 +634,7 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu,\n \timage->hp_action = hp_action;\n \n \t/* Now invoke arch-specific update handler */\n-\tarch_crash_handle_hotplug_event(image, arg);\n+\tarch_crash_handle_hotplug_event(image, cpu, arg);\n \n \t/* No longer handling a hotplug event */\n \timage->hp_action = KEXEC_CRASH_HP_NONE;\n", "prefixes": [ "RFC", "v1" ] }