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[2620:137:e000::1:18]) by mx.google.com with ESMTPS id 65-20020a630344000000b003825f9cfbcasi3137444pgd.776.2022.03.25.11.47.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Mar 2022 11:47:28 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=MErOErs0; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id DD04B1C5927; Fri, 25 Mar 2022 11:05:58 -0700 (PDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347499AbiCXNvI (ORCPT + 99 others); Thu, 24 Mar 2022 09:51:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345162AbiCXNvG (ORCPT ); Thu, 24 Mar 2022 09:51:06 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E659C1A3BF for ; Thu, 24 Mar 2022 06:49:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648129773; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k0wMgsnMHKgq7Pfa+baXddZSIWkD+5Ilm4xrgqfdVj0=; b=MErOErs0JTC59SWkfiTgMXkp7qdvhud1siDeC5hXAALGG9G658xPZ+fN/1XhzAyVM9ESn+ Iz3ROQXdHNNC2uztqUzhbgWKqs63IZ9I/VvgvoQA4LX1nwZH2Y0fe5muGuUszfFRqdKW4n ZkV2boGV6zH3+mISHu2Xew2QbqErDGk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-636-q9LdTwOiNWm8xN8YfUQQfQ-1; Thu, 24 Mar 2022 09:49:29 -0400 X-MC-Unique: q9LdTwOiNWm8xN8YfUQQfQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 02E0F3C1EA47; Thu, 24 Mar 2022 13:49:29 +0000 (UTC) Received: from localhost (ovpn-13-106.pek2.redhat.com [10.72.13.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 837522166B2D; Thu, 24 Mar 2022 13:49:15 +0000 (UTC) Date: Thu, 24 Mar 2022 21:49:11 +0800 From: Baoquan He To: Eric DeVolder Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [PATCH v5 4/8] crash: generic crash hotplug support infrastructure Message-ID: <20220324134911.GA354791@MiWiFi-R3L-srv> References: <20220303162725.49640-1-eric.devolder@oracle.com> <20220303162725.49640-5-eric.devolder@oracle.com> <20220324133856.GC354864@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324133856.GC354864@MiWiFi-R3L-srv> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/24/22 at 09:38pm, Baoquan He wrote: > On 03/03/22 at 11:27am, Eric DeVolder wrote: > > This patch introduces a generic crash hot plug/unplug infrastructure > > for CPU and memory changes. Upon CPU and memory changes, a generic > > crash_hotplug_handler() obtains the appropriate lock, does some > > important house keeping and then dispatches the hot plug/unplug event > > to the architecture specific arch_crash_hotplug_handler(), and when > > that handler returns, the lock is released. > > > > This patch modifies crash_core.c to implement a subsys_initcall() > > function that installs handlers for hot plug/unplug events. If CPU > > hotplug is enabled, then cpuhp_setup_state() is invoked to register a > > handler for CPU changes. Similarly, if memory hotplug is enabled, then > > register_memory_notifier() is invoked to install a handler for memory > > changes. These handlers in turn invoke the common generic handler > > crash_hotplug_handler(). > > > > On the CPU side, cpuhp_setup_state_nocalls() is invoked with parameter > > CPUHP_AP_ONLINE_DYN. While this works, when a CPU is being unplugged, > > the CPU still shows up in foreach_present_cpu() during the regeneration > > of the new CPU list, thus the need to explicitly check and exclude the > > soon-to-be offlined CPU in crash_prepare_elf64_headers(). > > > > On the memory side, each un/plugged memory block passes through the > > handler. For example, if a 1GiB DIMM is hotplugged, that generate 8 > > memory events, one for each 128MiB memblock. > > I rewrite the log as below with my understanding. Hope it's simpler to > help people get what's going on here. Please consider to take if it's > OK to you or adjust based on this. The code looks good to me. > Made some tuning: crash: add generic infrastructure for crash hotplug support Upon CPU and memory changes, a generic crash_hotplug_handler() is added to dispatch the hot plug/unplug event to the architecture specific arch_crash_hotplug_handler(). During the process, kexec_mutex need be held. To support cpu hotplug, one callback pair are registered to capture KEXEC_CRASH_HP_ADD_CPU and KEXEC_CRASH_HP_REMOVE_CPU events via cpuhp_setup_state_nocalls(). To support memory hotplug, a notifier crash_memhp_nb is registered to memory_chain to watch MEM_ONLINE and MEM_OFFLINE events. These callbacks and notifier will call crash_hotplug_handler() to handle captured event when invoked. > > > > > Signed-off-by: Eric DeVolder > > --- > > include/linux/kexec.h | 16 +++++++ > > kernel/crash_core.c | 108 ++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 124 insertions(+) > > > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > > index d7b59248441b..b11d75a6b2bc 100644 > > --- a/include/linux/kexec.h > > +++ b/include/linux/kexec.h > > @@ -300,6 +300,13 @@ struct kimage { > > > > /* Information for loading purgatory */ > > struct purgatory_info purgatory_info; > > + > > +#ifdef CONFIG_CRASH_HOTPLUG > > + bool hotplug_event; > > + int offlinecpu; > > + bool elf_index_valid; > > + int elf_index; > > +#endif > > #endif > > > > #ifdef CONFIG_IMA_KEXEC > > @@ -316,6 +323,15 @@ struct kimage { > > unsigned long elf_load_addr; > > }; > > > > +#ifdef CONFIG_CRASH_HOTPLUG > > +void arch_crash_hotplug_handler(struct kimage *image, > > + unsigned int hp_action, unsigned long a, unsigned long b); > > +#define KEXEC_CRASH_HP_REMOVE_CPU 0 > > +#define KEXEC_CRASH_HP_ADD_CPU 1 > > +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2 > > +#define KEXEC_CRASH_HP_ADD_MEMORY 3 > > +#endif /* CONFIG_CRASH_HOTPLUG */ > > + > > /* kexec interface functions */ > > extern void machine_kexec(struct kimage *image); > > extern int machine_kexec_prepare(struct kimage *image); > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > > index 256cf6db573c..76959d440f71 100644 > > --- a/kernel/crash_core.c > > +++ b/kernel/crash_core.c > > @@ -9,12 +9,17 @@ > > #include > > #include > > #include > > +#include > > +#include > > +#include > > > > #include > > #include > > > > #include > > > > +#include "kexec_internal.h" > > + > > /* vmcoreinfo stuff */ > > unsigned char *vmcoreinfo_data; > > size_t vmcoreinfo_size; > > @@ -491,3 +496,106 @@ static int __init crash_save_vmcoreinfo_init(void) > > } > > > > subsys_initcall(crash_save_vmcoreinfo_init); > > + > > +#ifdef CONFIG_CRASH_HOTPLUG > > +void __weak arch_crash_hotplug_handler(struct kimage *image, > > + unsigned int hp_action, unsigned long a, unsigned long b) > > +{ > > + pr_warn("crash hp: %s not implemented", __func__); > > +} > > + > > +static void crash_hotplug_handler(unsigned int hp_action, > > + unsigned long a, unsigned long b) > > +{ > > + /* Obtain lock while changing crash information */ > > + if (!mutex_trylock(&kexec_mutex)) > > + return; > > + > > + /* Check kdump is loaded */ > > + if (kexec_crash_image) { > > + pr_debug("crash hp: hp_action %u, a %lu, b %lu", hp_action, > > + a, b); > > + > > + /* Needed in order for the segments to be updated */ > > + arch_kexec_unprotect_crashkres(); > > + > > + /* Flag to differentiate between normal load and hotplug */ > > + kexec_crash_image->hotplug_event = true; > > + > > + /* Now invoke arch-specific update handler */ > > + arch_crash_hotplug_handler(kexec_crash_image, hp_action, a, b); > > + > > + /* No longer handling a hotplug event */ > > + kexec_crash_image->hotplug_event = false; > > + > > + /* Change back to read-only */ > > + arch_kexec_protect_crashkres(); > > + } > > + > > + /* Release lock now that update complete */ > > + mutex_unlock(&kexec_mutex); > > +} > > + > > +#if defined(CONFIG_MEMORY_HOTPLUG) > > +static int crash_memhp_notifier(struct notifier_block *nb, > > + unsigned long val, void *v) > > +{ > > + struct memory_notify *mhp = v; > > + unsigned long start, end; > > + > > + start = mhp->start_pfn << PAGE_SHIFT; > > + end = ((mhp->start_pfn + mhp->nr_pages) << PAGE_SHIFT) - 1; > > + > > + switch (val) { > > + case MEM_ONLINE: > > + crash_hotplug_handler(KEXEC_CRASH_HP_ADD_MEMORY, > > + start, end-start); > > + break; > > + > > + case MEM_OFFLINE: > > + crash_hotplug_handler(KEXEC_CRASH_HP_REMOVE_MEMORY, > > + start, end-start); > > + break; > > + } > > + return NOTIFY_OK; > > +} > > + > > +static struct notifier_block crash_memhp_nb = { > > + .notifier_call = crash_memhp_notifier, > > + .priority = 0 > > +}; > > +#endif > > + > > +#if defined(CONFIG_HOTPLUG_CPU) > > +static int crash_cpuhp_online(unsigned int cpu) > > +{ > > + crash_hotplug_handler(KEXEC_CRASH_HP_ADD_CPU, cpu, 0); > > + return 0; > > +} > > + > > +static int crash_cpuhp_offline(unsigned int cpu) > > +{ > > + crash_hotplug_handler(KEXEC_CRASH_HP_REMOVE_CPU, cpu, 0); > > + return 0; > > +} > > +#endif > > + > > +static int __init crash_hotplug_init(void) > > +{ > > + int result = 0; > > + > > +#if defined(CONFIG_MEMORY_HOTPLUG) > > + register_memory_notifier(&crash_memhp_nb); > > +#endif > > + > > +#if defined(CONFIG_HOTPLUG_CPU) > > + result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, > > + "crash/cpuhp", > > + crash_cpuhp_online, crash_cpuhp_offline); > > +#endif > > + > > + return result; > > +} > > + > > +subsys_initcall(crash_hotplug_init); > > +#endif /* CONFIG_CRASH_HOTPLUG */ > > -- > > 2.27.0 > > >