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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 D5C0EC433DB for ; Tue, 5 Jan 2021 08:28:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84FD122482 for ; Tue, 5 Jan 2021 08:28:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727402AbhAEI2X (ORCPT ); Tue, 5 Jan 2021 03:28:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727051AbhAEI2X (ORCPT ); Tue, 5 Jan 2021 03:28:23 -0500 Received: from mail-ed1-x52b.google.com (mail-ed1-x52b.google.com [IPv6:2a00:1450:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2887C061574 for ; Tue, 5 Jan 2021 00:27:42 -0800 (PST) Received: by mail-ed1-x52b.google.com with SMTP id dk8so30221298edb.1 for ; Tue, 05 Jan 2021 00:27:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tnuJ3Vz3ccZNW3+yMXMqfuw/KWVCwXk6iFyfNSeYrZM=; b=z/BkBKY3AuumYooa3zlwAkRPvbIhktpxqyHO9/Wio7o83beA8aqZsbHK6sYE9J4gmk qibjX6GFitZr3nkza0DFB3jP5dIwaRjdoPWZIbMEn00g8HYyFDuERW9/j2hdJmW4/MJr I0/19dP901dvPkrXB7dSRGqwHkuxO56RNn3R9PVuGaDmO4G9uTWd4Mva7CXPGVtN/9eL D4O3OXwLnALobvPbek7ZoJNWk0JXTNN56RgWsg1vxdBUQit9hvBMD0pQkhOJfqiGEggI q19NodP5zSFgNlUTPg3f1342ZpA1ryed/IdKoJpoWS3pPUdbNtNPk4rQi4Nhqg23Facx BKBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=tnuJ3Vz3ccZNW3+yMXMqfuw/KWVCwXk6iFyfNSeYrZM=; b=B4NvROK7u6uLXHPLRTERCI2QTd6kKBSKoxqg7mu35IPeECu9WSqZsj1iiUbBHV8JIs S0uxMmqHzrVqWSPHEGGXV6OEegcTpcBZGmAqhvUi/Bt0n8svos1LQ4Bvzu7Jv33E0GID l4dHfigL2cbKk0KwAPikhoGWCusW057rjqfQa+o4aBpI0m0gR3/kqKlu5ljlvlXS7zcw 6VEL60XaxdRa2pLVDh4S5Vz3x0dLCEtwEi5G4o/tAOwNrDnBCnUP7C8gJE9qfJM1Q59v b1Zf4MEi/U8PIxAtu8l3/rY8cnCmqsrHY3vbigmKPSuU6o9Gl9fI/H9prB1tyIvIDMPP hoaA== X-Gm-Message-State: AOAM532WkajNkLBjWO3hg1rdvfjdTm/V1GT0erMbTfWs0MzGyFlfiEz3 nbKzHNHDdeyQLBJWsDdAP2+fmToFViV8538L0AU1mQ== X-Google-Smtp-Source: ABdhPJweiOByDSltjQdldcPNJOZmyJ7nHVfo7+pBTlJq628wym3R1tWIfD6vOKBmFIy7kf1qEcuFe4CcP8ZDuZgV06A= X-Received: by 2002:aa7:cdc3:: with SMTP id h3mr19735149edw.52.1609835261574; Tue, 05 Jan 2021 00:27:41 -0800 (PST) MIME-Version: 1.0 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> <20210105081654.GU13207@dhcp22.suse.cz> In-Reply-To: <20210105081654.GU13207@dhcp22.suse.cz> From: Dan Williams Date: Tue, 5 Jan 2021 00:27:34 -0800 Message-ID: Subject: Re: uninitialized pmem struct pages To: Michal Hocko Cc: David Hildenbrand , Linux MM , LKML , Oscar Salvador Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 5, 2021 at 12:17 AM Michal Hocko wrote: > > 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()) { I assume that's onlince_section_nr(nr) in the version that compiles? This makes sense because the memory block size is larger than the section size. I suspect you have 1GB memory block size on this system, but since the System RAM and PMEM collide at a 512MB alignment in a memory block you end up walking the back end of the last 512MB of the System RAM memory block and run into the offline PMEM section. So, I don't think it's pfn_to_online_page that necessarily needs to know how to disambiguate each page, it's things that walk sections and memory blocks and expects them to be consistent over the span.