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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E72BDC433DB for ; Tue, 5 Jan 2021 08:16:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 617282222A for ; Tue, 5 Jan 2021 08:16:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 617282222A Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A86398D0065; Tue, 5 Jan 2021 03:16:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A36A68D0036; Tue, 5 Jan 2021 03:16:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 94D218D0065; Tue, 5 Jan 2021 03:16:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id 7C4D58D0036 for ; Tue, 5 Jan 2021 03:16:57 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 40EFA180AD807 for ; Tue, 5 Jan 2021 08:16:57 +0000 (UTC) X-FDA: 77671015674.27.stage80_12096cf274d7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 21F403D663 for ; Tue, 5 Jan 2021 08:16:57 +0000 (UTC) X-HE-Tag: stage80_12096cf274d7 X-Filterd-Recvd-Size: 5127 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Jan 2021 08:16:56 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1609834615; h=from:from:reply-to: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=zYLn+vdZQ/DSl04YjE7uuZY8XIpP1A4GnWwXJuDBAco=; b=cS8ev0d5S4LK7OsiiKLIWIoPz+jWMmhboAYLDPrCcXZS9NCBLHNjk/noR+dRBHtkC0wC6p zcbOjwgXTLKHf0OtaN3kNnsrPaUlXe8HTIex62mnE8HK2NbQymUFTUNqyGc7xsy4GKU6dT qv0qkuJOcz/jHhhcZSFs7UOzlRkp6Yw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 502FDAA35; Tue, 5 Jan 2021 08:16:55 +0000 (UTC) Date: Tue, 5 Jan 2021 09:16:54 +0100 From: Michal Hocko To: David Hildenbrand Cc: Dan Williams , linux-mm@kvack.org, LKML , Oscar Salvador Subject: Re: uninitialized pmem struct pages Message-ID: <20210105081654.GU13207@dhcp22.suse.cz> References: <20210104100323.GC13207@dhcp22.suse.cz> <033e1cd6-9762-5de6-3e88-47d3038fda7f@redhat.com> <20210104142624.GI13207@dhcp22.suse.cz> <23a4eea2-9fdb-fd1d-ee92-9cd8ac6e8f41@redhat.com> <20210104151005.GK13207@dhcp22.suse.cz> <26db2c3e-10c7-c6e3-23f7-21eb5101b31a@redhat.com> <20210104153300.GL13207@dhcp22.suse.cz> <6106ca7f-3247-0916-3e1e-ad6af17272ea@redhat.com> <20210105080057.GT13207@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210105080057.GT13207@dhcp22.suse.cz> 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 Tue 05-01-21 09:01:00, Michal Hocko wrote: > On Mon 04-01-21 16:44:52, David Hildenbrand wrote: > > On 04.01.21 16:43, David Hildenbrand wrote: > > > On 04.01.21 16:33, Michal Hocko wrote: > > >> On Mon 04-01-21 16:15:23, David Hildenbrand wrote: > > >>> On 04.01.21 16:10, Michal Hocko wrote: > > >> [...] > > >>> Do the physical addresses you see fall into the same section as boot > > >>> memory? Or what's around these addresses? > > >> > > >> Yes I am getting a garbage for the first struct page belonging to the > > >> pmem section [1] > > >> [ 0.020161] ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0x603fffffff] > > >> [ 0.020163] ACPI: SRAT: Node 4 PXM 4 [mem 0x6060000000-0x11d5fffffff] non-volatile > > >> > > >> The pfn without the initialized struct page is 0x6060000. This is a > > >> first pfn in a section. > > > > > > Okay, so we're not dealing with the "early section" mess I described, > > > different story. > > > > > > Due to [1], is_mem_section_removable() called > > > pfn_to_page(PHYS_PFN(0x6060000)). page_zone(page) made it crash, as not > > > initialized. > > > > > > Let's assume this is indeed a reserved pfn in the altmap. What's the > > > actual address of the memmap? > > > > > > I do wonder what hosts pfn_to_page(PHYS_PFN(0x6060000)) - is it actually > > > part of the actual altmap (i.e. > 0x6060000) or maybe even self-hosted? > > > > > > If it's not self-hosted, initializing the relevant memmaps should work > > > just fine I guess. Otherwise things get more complicated. > > > > Oh, I forgot: pfn_to_online_page() should at least in your example make > > sure other pfn walkers are safe. It was just an issue of > > is_mem_section_removable(). > > Hmm, I suspect you are right. I haven't put this together, thanks! The memory > section is indeed marked offline so pfn_to_online_page would indeed bail > out: > crash> p (0x6060000>>15) > $3 = 3084 > crash> p mem_section[3084/128][3084 & 127] > $4 = { > section_mem_map = 18446736128020054019, > usage = 0xffff902dcf956680, > page_ext = 0x0, > pad = 0 > } > crash> p 18446736128020054019 & (1UL<<2) > $5 = 0 > > That makes it considerably less of a problem than I thought! Forgot to add that those who are running kernels without 53cdc1cb29e8 ("drivers/base/memory.c: indicate all memory blocks as removable") for some reason can fix the crash by the following simple patch. Index: linux-5.3-users_mhocko_SLE15-SP2_for-next/drivers/base/memory.c =================================================================== --- linux-5.3-users_mhocko_SLE15-SP2_for-next.orig/drivers/base/memory.c +++ linux-5.3-users_mhocko_SLE15-SP2_for-next/drivers/base/memory.c @@ -152,9 +152,14 @@ static ssize_t removable_show(struct dev goto out; for (i = 0; i < sections_per_block; i++) { - if (!present_section_nr(mem->start_section_nr + i)) + unsigned long nr = mem->start_section_nr + i; + if (!present_section_nr(nr)) continue; - pfn = section_nr_to_pfn(mem->start_section_nr + i); + if (!online_section_nr()) { + ret = 0; + break; + } + pfn = section_nr_to_pfn(nr); ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION); } -- Michal Hocko SUSE Labs