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 3B476C4332F for ; Mon, 10 Jan 2022 08:05:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239739AbiAJIFX (ORCPT ); Mon, 10 Jan 2022 03:05:23 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:46146 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236425AbiAJIFP (ORCPT ); Mon, 10 Jan 2022 03:05:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1641801914; 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=gnfg0zplfFWqAUnnKnBRs+j7M9pGoVZQ/DoRm2CIx6Q=; b=EURPqcBjgpr+81LSwT70XfHpB/rsb8KlI+RBlgi7HPc+l39tIR6hzOnI9NJcX05Zvj2Coe 0K3lVLpl5Rfpkh3wpSQ+fsDfMnVAuN2ALMCerv+5hsN/yIs6f42CwxrAAWUJP95KmYumNf fm6cCwu4UBr+P2Z/twi99oiOE58uXjs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-288-Bkc1YkIcNZqmrsSzAEc9eQ-1; Mon, 10 Jan 2022 03:05:12 -0500 X-MC-Unique: Bkc1YkIcNZqmrsSzAEc9eQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DA88461246; Mon, 10 Jan 2022 08:05:09 +0000 (UTC) Received: from localhost (ovpn-12-198.pek2.redhat.com [10.72.12.198]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B158570D21; Mon, 10 Jan 2022 08:04:59 +0000 (UTC) Date: Mon, 10 Jan 2022 16:04:56 +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, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [RFC v2 0/6] crash: Kernel handling of CPU and memory hot un/plug Message-ID: <20220110080456.GG2731@MiWiFi-R3L-srv> References: <20211207195204.1582-1-eric.devolder@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Eric, On 01/05/22 at 08:25am, Eric DeVolder wrote: > Nudge... > > Fwiw, below is a working changeset to kexec userspace utility that allows the kexec_load > path to work similarly to the kexec_file_load path of this RFC. With both the following > userspace kexec patch and this RFC, both kexec_load and kexec_file_load work with changes > due to hotplug *without* unloading-then-reloading the kdump/capture kernel. Thanks for taking a try on that, and sorry for late response because of somethings at hand. I will review this v2 round. When applying them, I encountered some conflict, could you please rebase these on the ltest 5.16 and send me a tar ball privately, or a github branch is also welcome. Thanks in advance. Thanks Baoquan > > diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c > index 9826f6d..06adb7e 100644 > --- a/kexec/arch/i386/crashdump-x86.c > +++ b/kexec/arch/i386/crashdump-x86.c > @@ -48,6 +48,7 @@ > #include > > extern struct arch_options_t arch_options; > +extern unsigned long long hotplug_size; > > static int get_kernel_page_offset(struct kexec_info *UNUSED(info), > struct crash_elf_info *elf_info) > @@ -975,6 +976,13 @@ int load_crashdump_segments(struct kexec_info *info, char* mod_cmdline, > } else { > memsz = bufsz; > } > + > + /* If hotplug support enabled, use that size */ > + if (hotplug_size) { > + memsz = hotplug_size; > + } > + > + info->elfcorehdr = > elfcorehdr = add_buffer(info, tmp, bufsz, memsz, align, min_base, > max_addr, -1); > dbgprintf("Created elf header segment at 0x%lx\n", elfcorehdr); > diff --git a/kexec/kexec.c b/kexec/kexec.c > index f63b36b..9569d9a 100644 > --- a/kexec/kexec.c > +++ b/kexec/kexec.c > @@ -58,6 +58,7 @@ > > unsigned long long mem_min = 0; > unsigned long long mem_max = ULONG_MAX; > +unsigned long long hotplug_size = 0; > static unsigned long kexec_flags = 0; > /* Flags for kexec file (fd) based syscall */ > static unsigned long kexec_file_flags = 0; > @@ -672,6 +673,12 @@ static void update_purgatory(struct kexec_info *info) > if (info->segment[i].mem == (void *)info->rhdr.rel_addr) { > continue; > } > + /* Don't include elfcorehdr in the checksum, if hotplug > + * support enabled. > + */ > + if (hotplug_size && (info->segment[i].mem == (void *)info->elfcorehdr)) { > + continue; > + } > sha256_update(&ctx, info->segment[i].buf, > info->segment[i].bufsz); > nullsz = info->segment[i].memsz - info->segment[i].bufsz; > @@ -1504,6 +1511,17 @@ int main(int argc, char *argv[]) > case OPT_PRINT_CKR_SIZE: > print_crashkernel_region_size(); > return 0; > + case OPT_HOTPLUG_SIZE: > + /* Reserved the specified size for hotplug growth */ > + hotplug_size = strtoul(optarg, &endptr, 0); > + if (*endptr) { > + fprintf(stderr, > + "Bad option value in --hotplug-size=%s\n", > + optarg); > + usage(); > + return 1; > + } > + break; > default: > break; > } > diff --git a/kexec/kexec.h b/kexec/kexec.h > index 595dd68..b30dda4 100644 > --- a/kexec/kexec.h > +++ b/kexec/kexec.h > @@ -169,6 +169,7 @@ struct kexec_info { > int command_line_len; > > int skip_checks; > + unsigned long elfcorehdr; > }; > > struct arch_map_entry { > @@ -231,7 +232,8 @@ extern int file_types; > #define OPT_PRINT_CKR_SIZE 262 > #define OPT_LOAD_LIVE_UPDATE 263 > #define OPT_EXEC_LIVE_UPDATE 264 > -#define OPT_MAX 265 > +#define OPT_HOTPLUG_SIZE 265 > +#define OPT_MAX 266 > #define KEXEC_OPTIONS \ > { "help", 0, 0, OPT_HELP }, \ > { "version", 0, 0, OPT_VERSION }, \ > @@ -258,6 +260,7 @@ extern int file_types; > { "debug", 0, 0, OPT_DEBUG }, \ > { "status", 0, 0, OPT_STATUS }, \ > { "print-ckr-size", 0, 0, OPT_PRINT_CKR_SIZE }, \ > + { "hotplug-size", 2, 0, OPT_HOTPLUG_SIZE }, \ > > #define KEXEC_OPT_STR "h?vdfixyluet:pscaS" > > > > On 12/7/21 13:51, Eric DeVolder wrote: > > When the kdump service is loaded, if a CPU or memory is hot > > un/plugged, the crash elfcorehdr (for x86), which describes the CPUs > > and memory in the system, must also be updated, else the resulting > > vmcore is inaccurate (eg. missing either CPU context or memory > > regions). > > > > The current solution utilizes udev to initiate an unload-then-reload > > of the kdump image (e. kernel, initrd, boot_params, puratory and > > elfcorehdr) by the userspace kexec utility. In previous posts I have > > outlined the significant performance problems related to offloading > > this activity to userspace. > > > > This patchset introduces a generic crash hot un/plug handler that > > registers with the CPU and memory notifiers. Upon CPU or memory > > changes, this generic handler is invoked and performs important > > housekeeping, for example obtaining the appropriate lock, and then > > invokes an architecture specific handler to do the appropriate > > updates. > > > > In the case of x86_64, the arch specific handler generates a new > > elfcorehdr, and overwrites the old one in memory. No involvement > > with userspace needed. > > > > To realize the benefits/test this patchset, one must make a couple > > of minor changes to userspace: > > > > - Disable the udev rule for updating kdump on hot un/plug changes > > Eg. on RHEL: rm -f /usr/lib/udev/rules.d/98-kexec.rules > > or other technique to neuter the rule. > > > > - Change to the kexec_file_load for loading the kdump kernel: > > Eg. on RHEL: in /usr/bin/kdumpctl, change to: > > standard_kexec_args="-p -d -s" > > which adds the -s to select kexec_file_load syscall. > > > > This patchset supports kexec_load with a modified kexec userspace > > utility, on which I am current working to provide separately. > > > > Regards, > > eric > > --- > > RFC v2: 7dec2021 > > - Acting upon Baoquan He suggestion of removing elfcorehdr from > > the purgatory list of segments, removed purgatory code from > > patchset, and it is signficiantly simpler now. > > > > RFC v1: 18nov2021 > > https://lkml.org/lkml/2021/11/18/845 > > - working patchset demonstrating kernel handling of hotplug > > updates to x86 elfcorehdr for kexec_file_load > > > > RFC: 14dec2020 > > https://lkml.org/lkml/2020/12/14/532 > > - proposed concept of allowing kernel to handle hotplug update > > of elfcorehdr > > --- > > > > > > Eric DeVolder (6): > > crash: fix minor typo/bug in debug message > > crash hp: Introduce CRASH_HOTPLUG configuration options > > crash hp: definitions and prototype changes > > crash hp: generic crash hotplug support infrastructure > > crash hp: kexec_file changes for crash hotplug support > > crash hp: Add x86 crash hotplug support > > > > arch/x86/Kconfig | 26 ++++++++ > > arch/x86/kernel/crash.c | 140 +++++++++++++++++++++++++++++++++++++++- > > include/linux/kexec.h | 21 +++++- > > kernel/crash_core.c | 118 +++++++++++++++++++++++++++++++++ > > kernel/kexec_file.c | 15 ++++- > > 5 files changed, 314 insertions(+), 6 deletions(-) > > >