From mboxrd@z Thu Jan 1 00:00:00 1970 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 DB9E3C77B61 for ; Fri, 28 Apr 2023 09:26:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345261AbjD1J0S (ORCPT ); Fri, 28 Apr 2023 05:26:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229823AbjD1J0P (ORCPT ); Fri, 28 Apr 2023 05:26:15 -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 EDFCA30E8 for ; Fri, 28 Apr 2023 02:25:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1682673928; 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=QuA0sp3kPLTAsZbFHqKe9UmjDCeX3uXbQzydlzfRVOE=; b=I3Pldj29w1nru67npb6LCjMeYj8IF0h4+MRLgj1ncA1NtDPej1Zg9FDELfxUfWcH15oud2 YzS/5MqSeYapvnvNTjI+BoHoFEHOZmtR4aFVO5Q/q+gpolqlmXFegulNZbDxm6mDL8lo+y BAEaI84OeJeklwB3p5puZBbBac0L8bA= 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-428-uHpgIYk0MMua_cWE-cemCg-1; Fri, 28 Apr 2023 05:25:24 -0400 X-MC-Unique: uHpgIYk0MMua_cWE-cemCg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A79BC185A79C; Fri, 28 Apr 2023 09:25:23 +0000 (UTC) Received: from localhost (ovpn-12-57.pek2.redhat.com [10.72.12.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 99ABBC15BA0; Fri, 28 Apr 2023 09:25:22 +0000 (UTC) Date: Fri, 28 Apr 2023 17:25:18 +0800 From: Baoquan He To: Hari Bathini Cc: Eric DeVolder , 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, sourabhjain@linux.ibm.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [PATCH v21 5/7] x86/crash: add x86 crash hotplug support Message-ID: References: <20230404180326.6890-1-eric.devolder@oracle.com> <20230404180326.6890-6-eric.devolder@oracle.com> <409c8253-49b9-6993-f79e-8e6203ce4b31@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <409c8253-49b9-6993-f79e-8e6203ce4b31@linux.ibm.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/27/23 at 10:26pm, Hari Bathini wrote: > On 27/04/23 2:19 pm, Baoquan He wrote: > > On 04/27/23 at 12:39pm, Hari Bathini wrote: > > > Hi Eric, > > > > > > On 04/04/23 11:33 pm, Eric DeVolder wrote: > > > > When CPU or memory is hot un/plugged, or off/onlined, the crash > > > > elfcorehdr, which describes the CPUs and memory in the system, > > > > must also be updated. > > > > > > > > The segment containing the elfcorehdr is identified at run-time > > > > in crash_core:crash_handle_hotplug_event(), which works for both > > > > the kexec_load() and kexec_file_load() syscalls. A new elfcorehdr > > > > is generated from the available CPUs and memory into a buffer, > > > > and then installed over the top of the existing elfcorehdr. > > > > > > > > In the patch 'kexec: exclude elfcorehdr from the segment digest' > > > > the need to update purgatory due to the change in elfcorehdr was > > > > eliminated. As a result, no changes to purgatory or boot_params > > > > (as the elfcorehdr= kernel command line parameter pointer > > > > remains unchanged and correct) are needed, just elfcorehdr. > > > > > > > > To accommodate a growing number of resources via hotplug, the > > > > elfcorehdr segment must be sufficiently large enough to accommodate > > > > changes, see the CRASH_MAX_MEMORY_RANGES description. This is used > > > > only on the kexec_file_load() syscall; for kexec_load() userspace > > > > will need to size the segment similarly. > > > > > > > > To accommodate kexec_load() syscall in the absence of > > > > > > Firstly, thanks! This series is a nice improvement to kdump support > > > in hotplug environment. > > > > > > One concern though is that this change assumes corresponding support > > > in kexec-tools. Without that support kexec_load would fail to boot > > > with digest verification failure, iiuc. > > > > Eric has posted patchset to modify kexec_tools to support that, please > > see the link Eric pasted in the cover letter. > > > > http://lists.infradead.org/pipermail/kexec/2022-October/026032.html > > Right, Baoquan. > > I did see that and if I read the code correctly, without that patchset > kexec_load would fail. Not with an explicit error that hotplug support > is missing or such but it would simply fail to boot into capture kernel > with digest verification failure. > > My suggestion was to avoid that userspace tool breakage for older > kexec-tools version by introducing a new kexec flag that can tell > kernel that kexec-tools is ready to use this in-kernel update support. > So, if kexec_load happens without the flag, avoid doing an in-kernel > update on hotplug. I hope that clears the confusion. Yeah, sounds like a good idea. It may be extended in later patch.