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[2620:137:e000::1:20]) by mx.google.com with ESMTP id ot5-20020a170906ccc500b006e002ecc82esi525496ejb.45.2022.03.24.14.05.56; Thu, 24 Mar 2022 14:06:22 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=H31eiXa1; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235743AbiCXOfc (ORCPT + 99 others); Thu, 24 Mar 2022 10:35:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351233AbiCXOfG (ORCPT ); Thu, 24 Mar 2022 10:35:06 -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 51CCF9F3BA for ; Thu, 24 Mar 2022 07:33:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648132390; 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=uz406a5kGDv/VDVK5JX7oOinepQMkPu5YbTVYOJzd5o=; b=H31eiXa1vNmv9MuiJybfRYsxe1QlMTF6kDx4ijgWBf2T00WI7TE1ptGmVw9n6dOExPdDyI A2+IlQrHDiAH5a6YIVJ4krdkfRPWjKZIV8yTBti+v1S6G70bJNkk3e77lCecAHGJlFe+/a fHvrHuHBnlSuv6N64b27CyhuPDSlVNQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-542-fwzimZlrNg-y3odw3Q2how-1; Thu, 24 Mar 2022 10:33:06 -0400 X-MC-Unique: fwzimZlrNg-y3odw3Q2how-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2E87118E52C0; Thu, 24 Mar 2022 14:33:05 +0000 (UTC) Received: from localhost (ovpn-13-106.pek2.redhat.com [10.72.13.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CEDE940D296B; Thu, 24 Mar 2022 14:33:03 +0000 (UTC) Date: Thu, 24 Mar 2022 22:33:00 +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: <20220324143300.GD354864@MiWiFi-R3L-srv> References: <20220303162725.49640-1-eric.devolder@oracle.com> <20220303162725.49640-5-eric.devolder@oracle.com> <20220324133856.GC354864@MiWiFi-R3L-srv> <20220324134911.GA354791@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 X-Spam-Status: No, score=-3.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=ham 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 08:53am, Eric DeVolder wrote: > Baoquan, > Thanks, I've offered a minor correction below. > eric > > On 3/24/22 08:49, Baoquan He wrote: > > 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(). > s/KEXEC_CRASH_HP_ADD}REMOVE_CPU/CPUHP_AP_ONLINE_DYN/ as the KEXEC_CRASH are the > names I've introduced with this patch? Right. While checking it, I notice hp_action which you don't use actually. Can you reconsider that part of design, the hp_action, the a, b parameter passed to handler? > > > > > 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 > > > > > > > > > >