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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52732C433EF for ; Wed, 6 Oct 2021 00:36:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E22BD6120C for ; Wed, 6 Oct 2021 00:36:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E22BD6120C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 7D4EF6B0073; Tue, 5 Oct 2021 20:36:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7844E6B0074; Tue, 5 Oct 2021 20:36:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 69B4A900002; Tue, 5 Oct 2021 20:36:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0065.hostedemail.com [216.40.44.65]) by kanga.kvack.org (Postfix) with ESMTP id 5D08D6B0073 for ; Tue, 5 Oct 2021 20:36:03 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1C9368249980 for ; Wed, 6 Oct 2021 00:36:03 +0000 (UTC) X-FDA: 78664145406.26.31CA016 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf06.hostedemail.com (Postfix) with ESMTP id B7DAD801BEF4 for ; Wed, 6 Oct 2021 00:36:02 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id A6F5261207; Wed, 6 Oct 2021 00:35:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633480561; bh=8xj9E6op+Rg8PTXffqt5Iu6I5QYdPwtUpE27T1OKFzU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iu6vyfwg4W/tfIH5vF6EJ8rw4IAH6oyZstjQ+k71TftnxAoc/pd8Vg7g809vYXSmw HqBqPXNn18TKQQVolBCdPUBQNjbRZENvt/N4z6bD5KXEN7vh2A1ska4yQbc/iG3LBv 9+PzqFOlfYw7EWsnTtgXQ3BetmXc3txVFFIYY2newPWMttQOXa9Z5OdONOzRjfJewv OlVGXBfO8XkC/k/4KN1DjHTDnLNTp55uKMab8YAyYWXAnirslZET9T3W1dieK8A9Lt f858nm0SZ+QfOwVHGG2EUsgGuL7mfwROiNowH7gIpRq8xDCM3duxbib9wjTXMRsty9 9ElPf2xXwHi1w== Date: Tue, 5 Oct 2021 17:35:57 -0700 From: Mike Rapoport To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Oscar Salvador , Jianyong Wu , "Aneesh Kumar K . V" , Vineet Gupta , Geert Uytterhoeven , Huacai Chen , Jiaxun Yang , Thomas Bogendoerfer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Eric Biederman , Arnd Bergmann , linux-snps-arc@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-s390@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org Subject: Re: [PATCH v2 2/5] memblock: improve MEMBLOCK_HOTPLUG documentation Message-ID: References: <20211004093605.5830-1-david@redhat.com> <20211004093605.5830-3-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211004093605.5830-3-david@redhat.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B7DAD801BEF4 X-Stat-Signature: kqi697bdrrxf5p5xazkcib8mc8ozihhy Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=iu6vyfwg; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf06.hostedemail.com: domain of rppt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=rppt@kernel.org X-HE-Tag: 1633480562-822433 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 04, 2021 at 11:36:02AM +0200, David Hildenbrand wrote: > The description of MEMBLOCK_HOTPLUG is currently short and consequently > misleading: we're actually dealing with a memory region that might get > hotunplugged later (i.e., the platform+firmware supports it), yet it is > indicated in the firmware-provided memory map as system ram that will just > get used by the system for any purpose when not taking special care. The > firmware marked this memory region as a hot(un)plugged (e.g., hotplugged > before reboot), implying that it might get hotunplugged again later. > > Whether we consider this information depends on the "movable_node" kernel > commandline parameter: only with "movable_node" set, we'll try keeping > this memory hotunpluggable, for example, by not serving early allocations > from this memory region and by letting the buddy manage it using the > ZONE_MOVABLE. > > Let's make this clearer by extending the documentation. > > Note: kexec *has to* indicate this memory to the second kernel. With > "movable_node" set, we don't want to place kexec-images on this memory. > Without "movable_node" set, we don't care and can place kexec-images on > this memory. In both cases, after successful memory hotunplug, kexec has to > be re-armed to update the memory map for the second kernel and to place the > kexec-images somewhere else. > > Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport > --- > include/linux/memblock.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index 34de69b3b8ba..4ee8dd2d63a7 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -28,7 +28,11 @@ extern unsigned long long max_possible_pfn; > /** > * enum memblock_flags - definition of memory region attributes > * @MEMBLOCK_NONE: no special request > - * @MEMBLOCK_HOTPLUG: hotpluggable region > + * @MEMBLOCK_HOTPLUG: memory region indicated in the firmware-provided memory > + * map during early boot as hot(un)pluggable system RAM (e.g., memory range > + * that might get hotunplugged later). With "movable_node" set on the kernel > + * commandline, try keeping this memory region hotunpluggable. Does not apply > + * to memblocks added ("hotplugged") after early boot. > * @MEMBLOCK_MIRROR: mirrored region > * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as > * reserved in the memory map; refer to memblock_mark_nomap() description > -- > 2.31.1 > -- Sincerely yours, Mike.