Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF20BC7618A for ; Mon, 20 Mar 2023 08:14:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229776AbjCTIO3 (ORCPT ); Mon, 20 Mar 2023 04:14:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230357AbjCTIOM (ORCPT ); Mon, 20 Mar 2023 04:14:12 -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 ESMTPS id 6F204359B for ; Mon, 20 Mar 2023 01:13:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679299990; 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; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230317212128.21424-3-eric.devolder@oracle.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/17/23 at 05:21pm, Eric DeVolder wrote: ...... > @@ -697,3 +700,137 @@ static int __init crash_save_vmcoreinfo_init(void) > } > > subsys_initcall(crash_save_vmcoreinfo_init); > + > +#ifdef CONFIG_CRASH_HOTPLUG > +#undef pr_fmt > +#define pr_fmt(fmt) "crash hp: " fmt > +/* > + * To accurately reflect hot un/plug changes of cpu and memory resources > + * (including onling and offlining of those resources), the elfcorehdr > + * (which is passed to the crash kernel via the elfcorehdr= parameter) > + * must be updated with the new list of CPUs and memories. > + * > + * In order to make changes to elfcorehdr, two conditions are needed: > + * First, the segment containing the elfcorehdr must be large enough > + * to permit a growing number of resources; the elfcorehdr memory size > + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES. > + * Second, purgatory must explicitly exclude the elfcorehdr from the > + * list of segments it checks (since the elfcorehdr changes and thus > + * would require an update to purgatory itself to update the digest). > + */ > +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu) > +{ > + /* Obtain lock while changing crash information */ > + if (!kexec_trylock()) > + return; > + > + /* Check kdump is loaded */ > + if (kexec_crash_image) { Here, what I mean is: /* Obtain lock while changing crash information */ if (!kexec_trylock()) return; /*If kdump is not loaded*/ if (!kexec_crash_image) goto out; Then we reduce one tab of indentation for the following code block, e.g the for loop block will have smaller pressure on breaking the 80 chars limitation. > + struct kimage *image = kexec_crash_image; > + > + if (hp_action == KEXEC_CRASH_HP_ADD_CPU || > + hp_action == KEXEC_CRASH_HP_REMOVE_CPU) > + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu); > + else > + pr_debug("hp_action %u\n", hp_action); > + > + /* > + * When the struct kimage is allocated, the elfcorehdr_index > + * is set to -1. Find the segment containing the elfcorehdr, > + * if not already found. This works for both the kexec_load > + * and kexec_file_load paths. > + */ > + if (image->elfcorehdr_index < 0) { > + unsigned long mem; > + unsigned char *ptr; > + unsigned int n; > + > + for (n = 0; n < image->nr_segments; n++) { > + mem = image->segment[n].mem; > + ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT)); > + if (ptr) { > + /* The segment containing elfcorehdr */ > + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) > + image->elfcorehdr_index = (int)n; > + kunmap_local(ptr); > + } > + } > + } > + > + if (image->elfcorehdr_index < 0) { > + pr_err("unable to locate elfcorehdr segment"); > + goto out; > + } > + > + /* Needed in order for the segments to be updated */ > + arch_kexec_unprotect_crashkres(); > + > + /* Differentiate between normal load and hotplug update */ > + image->hp_action = hp_action; > + > + /* Now invoke arch-specific update handler */ > + arch_crash_handle_hotplug_event(image); > + > + /* No longer handling a hotplug event */ > + image->hp_action = KEXEC_CRASH_HP_NONE; > + image->elfcorehdr_updated = true; > + > + /* Change back to read-only */ > + arch_kexec_protect_crashkres(); > + } > + > +out: > + /* Release lock now that update complete */ > + kexec_unlock(); > +} > + > +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v) > +{ > + switch (val) { > + case MEM_ONLINE: > + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY, > + KEXEC_CRASH_HP_INVALID_CPU); > + break; > + > + case MEM_OFFLINE: > + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY, > + KEXEC_CRASH_HP_INVALID_CPU); > + break; > + } > + return NOTIFY_OK; > +} > + > +static struct notifier_block crash_memhp_nb = { > + .notifier_call = crash_memhp_notifier, > + .priority = 0 > +}; > + > +static int crash_cpuhp_online(unsigned int cpu) > +{ > + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu); > + return 0; > +} > + > +static int crash_cpuhp_offline(unsigned int cpu) > +{ > + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu); > + return 0; > +} > + > +static int __init crash_hotplug_init(void) > +{ > + int result = 0; > + > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) > + register_memory_notifier(&crash_memhp_nb); > + > + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) { > + result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN, > + "crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline); > + } > + > + return result; > +} > + > +subsys_initcall(crash_hotplug_init); > +#endif > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index 3d578c6fefee..8296d019737c 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -277,6 +277,12 @@ struct kimage *do_kimage_alloc_init(void) > /* Initialize the list of unusable pages */ > INIT_LIST_HEAD(&image->unusable_pages); > > +#ifdef CONFIG_CRASH_HOTPLUG > + image->hp_action = KEXEC_CRASH_HP_NONE; > + image->elfcorehdr_index = -1; > + image->elfcorehdr_updated = false; > +#endif > + > return image; > } > > -- > 2.31.1 >