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=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 B09BCC433E0 for ; Mon, 1 Feb 2021 14:32:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 35CD964E56 for ; Mon, 1 Feb 2021 14:32:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 35CD964E56 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 889096B0080; Mon, 1 Feb 2021 09:32:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 83A2D6B0081; Mon, 1 Feb 2021 09:32:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7273C6B0083; Mon, 1 Feb 2021 09:32:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0058.hostedemail.com [216.40.44.58]) by kanga.kvack.org (Postfix) with ESMTP id 5A24E6B0080 for ; Mon, 1 Feb 2021 09:32:49 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1A6EA1EE6 for ; Mon, 1 Feb 2021 14:32:49 +0000 (UTC) X-FDA: 77769940458.25.angle46_0a1216b275c2 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id B4DB41804E3B5 for ; Mon, 1 Feb 2021 14:32:48 +0000 (UTC) X-HE-Tag: angle46_0a1216b275c2 X-Filterd-Recvd-Size: 7212 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Mon, 1 Feb 2021 14:32:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612189967; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ljqvXX+/v7ItzDm31rzeq5jT4gYfoSDTG2W9G3iEdcM=; b=fNw4BFiXY2uydwvs6QuxtIslOaWqwZnzWNm4GtHIzSKEzBqKa0ZVDZ9KBR5IC99psuYwef FSMbLV/75ozqS4nf4B2Y9CrZrZE7HxNi0uo/+4YAJIJDhWHQUNHuGKVTzwrnxdN/teM0xk l6hqxuaUAgzHa03PXXA6tVKsbKAFmeQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-114-AiwFcXaZNkiW5xntkpbzVw-1; Mon, 01 Feb 2021 09:32:43 -0500 X-MC-Unique: AiwFcXaZNkiW5xntkpbzVw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A481F8049CD; Mon, 1 Feb 2021 14:32:40 +0000 (UTC) Received: from [10.36.115.24] (ovpn-115-24.ams2.redhat.com [10.36.115.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id C5438614FC; Mon, 1 Feb 2021 14:32:34 +0000 (UTC) Subject: Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory To: Mike Rapoport Cc: Andrew Morton , Andrea Arcangeli , Baoquan He , Borislav Petkov , Chris Wilson , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , =?UTF-8?Q?=c5=81ukasz_Majczak?= , Mel Gorman , Michal Hocko , Mike Rapoport , Qian Cai , "Sarvela, Tomi P" , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org References: <20210130221035.4169-1-rppt@kernel.org> <20210130221035.4169-2-rppt@kernel.org> <56e2c568-b121-8860-a6b0-274ace46d835@redhat.com> <20210201143014.GI242749@kernel.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <759698b8-ac81-de31-4916-023d8dfa9fe5@redhat.com> Date: Mon, 1 Feb 2021 15:32:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20210201143014.GI242749@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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 01.02.21 15:30, Mike Rapoport wrote: > On Mon, Feb 01, 2021 at 10:32:44AM +0100, David Hildenbrand wrote: >> On 30.01.21 23:10, Mike Rapoport wrote: >>> From: Mike Rapoport >>> >>> The physical memory on an x86 system starts at address 0, but this is not >>> always reflected in e820 map. For example, the BIOS can have e820 entries >>> like >>> >>> [ 0.000000] BIOS-provided physical RAM map: >>> [ 0.000000] BIOS-e820: [mem 0x0000000000001000-0x000000000009ffff] usable >>> >>> or >>> >>> [ 0.000000] BIOS-provided physical RAM map: >>> [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x0000000000000fff] reserved >>> [ 0.000000] BIOS-e820: [mem 0x0000000000001000-0x0000000000057fff] usable >>> >>> In either case, e820__memblock_setup() won't add the range 0x0000 - 0x1000 >>> to memblock.memory and later during memory map initialization this range is >>> left outside any zone. >>> >>> With SPARSEMEM=y there is always a struct page for pfn 0 and this struct >>> page will have it's zone link wrong no matter what value will be set there. >>> >>> To avoid this inconsistency, add the beginning of RAM to memblock.memory. >>> Limit the added chunk size to match the reserved memory to avoid >>> registering memory that may be used by the firmware but never reserved at >>> e820__memblock_setup() time. >>> >>> Fixes: bde9cfa3afe4 ("x86/setup: don't remove E820_TYPE_RAM for pfn 0") >>> Signed-off-by: Mike Rapoport >>> Cc: stable@vger.kernel.org >>> --- >>> arch/x86/kernel/setup.c | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c >>> index 3412c4595efd..67c77ed6eef8 100644 >>> --- a/arch/x86/kernel/setup.c >>> +++ b/arch/x86/kernel/setup.c >>> @@ -727,6 +727,14 @@ static void __init trim_low_memory_range(void) >>> * Kconfig help text for X86_RESERVE_LOW. >>> */ >>> memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE)); >>> + >>> + /* >>> + * Even if the firmware does not report the memory at address 0 as >>> + * usable, inform the generic memory management about its existence >>> + * to ensure it is a part of ZONE_DMA and the memory map for it is >>> + * properly initialized. >>> + */ >>> + memblock_add(0, ALIGN(reserve_low, PAGE_SIZE)); >>> } >>> >>> /* >>> >> >> I think, to make that code more robust, and to not rely on archs to do the >> right thing, we should do something like >> >> 1) Make sure in free_area_init() that each PFN with a memmap (i.e., falls >> into a partial present section) is spanned by a zone; that would include PFN >> 0 in this case. >> >> 2) In init_zone_unavailable_mem(), similar to round_up(max_pfn, >> PAGES_PER_SECTION) handling, consider range >> [round_down(min_pfn, PAGES_PER_SECTION), min_pfn - 1] >> which would handle in the x86-64 case [0..0] and, therefore, initialize PFN >> 0. >> >> Also, I think the special-case of PFN 0 is analogous to the >> round_up(max_pfn, PAGES_PER_SECTION) handling in >> init_zone_unavailable_mem(): who guarantees that these PFN above the highest >> present PFN are actually spanned by a zone? >> >> I'd suggest going through all zone ranges in free_area_init() first, dealing >> with zones that have "not section aligned start/end", clamping them up/down >> if required such that no holes within a section are left uncovered by a >> zone. > > I thought about changing the way zone extents are calculated so that zone > start/end will be always on a section boundary, but zone->zone_start_pfn > depends on node->node_start_pfn which is defined by hardware and expanding > a node to make its start pfn aligned at the section boundary might violate > the HW addressing scheme. > > Maybe this could never happen, or maybe it's not really important as the > pages there will be reserved anyway, but I'm not sure I can estimate all > the implications. > I'm suggesting to let zone (+node?) ranges cover memory holes with a valid memmap. Not to move actual memory between nodes/zones. -- Thanks, David / dhildenb