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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF06BC43461 for ; Fri, 11 Sep 2020 15:28:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B963C221E7 for ; Fri, 11 Sep 2020 15:28:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726228AbgIKP2x (ORCPT ); Fri, 11 Sep 2020 11:28:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:56244 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726074AbgIKPZa (ORCPT ); Fri, 11 Sep 2020 11:25:30 -0400 Received: from gaia (unknown [46.69.195.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6128A22268; Fri, 11 Sep 2020 14:06:07 +0000 (UTC) Date: Fri, 11 Sep 2020 15:06:04 +0100 From: Catalin Marinas To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Will Deacon , Mark Rutland , Marc Zyngier , Steve Capper , Mark Brown , linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] arm64/hotplug: Improve memory offline event notifier Message-ID: <20200911140603.GB12835@gaia> References: <1598241869-28416-1-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1598241869-28416-1-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Anshuman, On Mon, Aug 24, 2020 at 09:34:29AM +0530, Anshuman Khandual wrote: > This brings about three different changes to the sole memory event notifier > for arm64 platform and improves it's robustness while also enhancing debug > capabilities during potential memory offlining error conditions. > > This moves the memory notifier registration bit earlier in the boot process > from device_initcall() to setup_arch() which will help in guarding against > potential early boot memory offline requests. > > This enables MEM_OFFLINE memory event handling. It will help intercept any > possible error condition such as if boot memory some how still got offlined > even after an expilicit notifier failure, potentially by a future change in > generic hotplug framework. This would help detect such scenarious and help > debug further. > > It also adds a validation function which scans entire boot memory and makes > sure that early memory sections are online. This check is essential for the > memory notifier to work properly as it cannot prevent boot memory offlining > if they are not online to begin with. But this additional sanity check is > enabled only with DEBUG_VM. Could you please split this in separate patches rather than having a single one doing three somewhat related things? > --- a/arch/arm64/kernel/setup.c > +++ b/arch/arm64/kernel/setup.c > @@ -376,6 +376,14 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p) > "This indicates a broken bootloader or old kernel\n", > boot_args[1], boot_args[2], boot_args[3]); > } > + > + /* > + * Register the memory notifier which will prevent boot > + * memory offlining requests - early enough. But there > + * should not be any actual offlinig request till memory > + * block devices are initialized with memory_dev_init(). > + */ > + memory_hotremove_notifier(); Why can this not be an early_initcall()? As you said, memory_dev_init() is called much later, after the SMP was initialised. You could even combine this with validate_bootmem_online_state() in a single early_initcall() which, after checking, registers the notifier. -- Catalin