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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 0B400C433DB for ; Tue, 5 Jan 2021 08:01:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9C00C2222A for ; Tue, 5 Jan 2021 08:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C00C2222A 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 008AC8D0064; Tue, 5 Jan 2021 03:01:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EFA918D0036; Tue, 5 Jan 2021 03:01:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DEAA88D0064; Tue, 5 Jan 2021 03:01:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0088.hostedemail.com [216.40.44.88]) by kanga.kvack.org (Postfix) with ESMTP id C88508D0036 for ; Tue, 5 Jan 2021 03:01:00 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6DC18180AD811 for ; Tue, 5 Jan 2021 08:01:00 +0000 (UTC) X-FDA: 77670975480.21.nerve30_0a0d6fc274d7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 4833A180442C0 for ; Tue, 5 Jan 2021 08:01:00 +0000 (UTC) X-HE-Tag: nerve30_0a0d6fc274d7 X-Filterd-Recvd-Size: 3962 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Jan 2021 08:00:59 +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=1609833658; 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=Cxzc/0CIZcZEmpb9K49ULZp9Lus4XR9wQN99vW/8obc=; b=Cl8Uf9tN0gtBVJsbvIpCRCx9qoawwjvMgTXARJP5gEx1IB7O/nXbTZkR+Kh0fr0NfgHr/5 W6aZ5dAfMVd7miYPQmwPeJKjpysGd91RsTIZ1CoCnGuCh3Gp3z+g4622YDHHoojRuS9mK2 adR4z8weKtEJ1LrOo53k7Jz34wgWJZ0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 99930AA35; Tue, 5 Jan 2021 08:00:58 +0000 (UTC) Date: Tue, 5 Jan 2021 09:00:57 +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: <20210105080057.GT13207@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6106ca7f-3247-0916-3e1e-ad6af17272ea@redhat.com> 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 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! Thanks David! -- Michal Hocko SUSE Labs