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,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 4FD76C433DB for ; Mon, 1 Feb 2021 11:26:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BDF1164DD9 for ; Mon, 1 Feb 2021 11:26:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BDF1164DD9 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 1BE396B0071; Mon, 1 Feb 2021 06:26:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1484C6B0072; Mon, 1 Feb 2021 06:26:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 00FB36B0075; Mon, 1 Feb 2021 06:26:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id DD0266B0071 for ; Mon, 1 Feb 2021 06:26:26 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 94936181AEF10 for ; Mon, 1 Feb 2021 11:26:26 +0000 (UTC) X-FDA: 77769470772.07.money56_1e07ef2275c1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 79F7A1803F9A4 for ; Mon, 1 Feb 2021 11:26:26 +0000 (UTC) X-HE-Tag: money56_1e07ef2275c1 X-Filterd-Recvd-Size: 6451 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Mon, 1 Feb 2021 11:26:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612178785; 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=gxLqvpXl3gUUeGQW/1robjY+CzCVzkMk/eTpCkIzHRM=; b=i0k/zCyPxr0lOi+OqjxwRzX+6VcZBVMAL08ehWa+E0+Z1jUdhudhXn/2rR0rhwYq3j/tHY iNcqKTOHZaFGAtxOxF6DhyEa2VybTNfrnPZLznWYbgEZX54rUkfoK1Bgly2b5bLWf1y9TW g+8amF6uHmLaUNYteK/rsf7vJNv472s= 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-601-r3qRBkhxPiGwKEzbg3uhgQ-1; Mon, 01 Feb 2021 06:26:21 -0500 X-MC-Unique: r3qRBkhxPiGwKEzbg3uhgQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1FDAC107ACF5; Mon, 1 Feb 2021 11:26:13 +0000 (UTC) Received: from localhost (ovpn-12-141.pek2.redhat.com [10.72.12.141]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C9A095C5AE; Mon, 1 Feb 2021 11:26:07 +0000 (UTC) Date: Mon, 1 Feb 2021 19:26:05 +0800 From: Baoquan He To: David Hildenbrand Cc: Mike Rapoport , Andrew Morton , Andrea Arcangeli , 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 Subject: Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory Message-ID: <20210201112605.GA2357@MiWiFi-R3L-srv> References: <20210130221035.4169-1-rppt@kernel.org> <20210130221035.4169-2-rppt@kernel.org> <56e2c568-b121-8860-a6b0-274ace46d835@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56e2c568-b121-8860-a6b0-274ace46d835@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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 02/01/21 at 10:32am, 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. Sounds reasonable. Maybe we can change to get the real expected lowest pfn from find_min_pfn_for_node() by iterating memblock.memory and memblock.reserved and comparing. > > 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. > > -- > Thanks, > > David / dhildenb