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=-17.5 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,URIBL_BLOCKED,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 D32F4C433DB for ; Tue, 12 Jan 2021 10:02:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4F08B206FA for ; Tue, 12 Jan 2021 10:02:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F08B206FA 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 B18E18D0089; Tue, 12 Jan 2021 05:02:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AEDC18D0051; Tue, 12 Jan 2021 05:02:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 98F188D0089; Tue, 12 Jan 2021 05:02:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0115.hostedemail.com [216.40.44.115]) by kanga.kvack.org (Postfix) with ESMTP id 8245E8D0051 for ; Tue, 12 Jan 2021 05:02:02 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 4CAFF181AEF00 for ; Tue, 12 Jan 2021 10:02:02 +0000 (UTC) X-FDA: 77696682084.25.nerve08_540331a27514 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id 2B45C1804E3A1 for ; Tue, 12 Jan 2021 10:02:02 +0000 (UTC) X-HE-Tag: nerve08_540331a27514 X-Filterd-Recvd-Size: 9479 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Tue, 12 Jan 2021 10:02:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610445720; 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=jokJeSk3P3/zS0po8V8SDHCNSJMd/Zkjc2TQWQ0eDns=; b=fYkoCGxw9hqkl63w5dCAbb9H8cET1f3nWX++Zd95Lu1gxNjL9WN9+T6uP2poaNjHJ0ZK09 HqCnN+6uf+nDNhhsRfDOaL3vJZc/nrMWgQG/GpAu9cDe6LiZVNpd2rBqawGEgSK+XSdaxS ESW2FLN7HJHhg2gBJhQja6M4usgRFt8= 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-430-9jgz1gmjPA26FJ-qrrbUgA-1; Tue, 12 Jan 2021 05:01:56 -0500 X-MC-Unique: 9jgz1gmjPA26FJ-qrrbUgA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 05BED879512; Tue, 12 Jan 2021 10:01:55 +0000 (UTC) Received: from [10.36.115.140] (ovpn-115-140.ams2.redhat.com [10.36.115.140]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6117F5D9DB; Tue, 12 Jan 2021 10:01:53 +0000 (UTC) Subject: Re: [PATCH v2 3/5] mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions To: Dan Williams , linux-mm@kvack.org Cc: Andrew Morton , Michal Hocko , vishal.l.verma@intel.com, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org References: <161044407603.1482714.16630477578392768273.stgit@dwillia2-desk3.amr.corp.intel.com> <161044409294.1482714.434561066315039753.stgit@dwillia2-desk3.amr.corp.intel.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Tue, 12 Jan 2021 11:01:52 +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: <161044409294.1482714.434561066315039753.stgit@dwillia2-desk3.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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 12.01.21 10:34, Dan Williams wrote: > While pfn_to_online_page() is able to determine pfn_valid() at > subsection granularity it is not able to reliably determine if a given > pfn is also online if the section is mixes ZONE_{NORMAL,MOVABLE} with > ZONE_DEVICE. This means that pfn_to_online_page() may return invalid > @page objects. For example with a memory map like: > > 100000000-1fbffffff : System RAM > 142000000-143002e16 : Kernel code > 143200000-143713fff : Kernel rodata > 143800000-143b15b7f : Kernel data > 144227000-144ffffff : Kernel bss > 1fc000000-2fbffffff : Persistent Memory (legacy) > 1fc000000-2fbffffff : namespace0.0 > > This command: > > echo 0x1fc000000 > /sys/devices/system/memory/soft_offline_page > > ...succeeds when it should fail. When it succeeds it touches > an uninitialized page and may crash or cause other damage (see > dissolve_free_huge_page()). > > While the memory map above is contrived via the memmap=ss!nn kernel > command line option, the collision happens in practice on shipping > platforms. The memory controller resources that decode spans of > physical address space are a limited resource. One technique > platform-firmware uses to conserve those resources is to share a decoder > across 2 devices to keep the address range contiguous. Unfortunately the > unit of operation of a decoder is 64MiB while the Linux section size is > 128MiB. This results in situations where, without subsection hotplug > memory mappings with different lifetimes collide into one object that > can only express one lifetime. > > Update move_pfn_range_to_zone() to flag (SECTION_TAINT_ZONE_DEVICE) a > section that mixes ZONE_DEVICE pfns with other online pfns. With > SECTION_TAINT_ZONE_DEVICE to delineate, pfn_to_online_page() can fall > back to a slow-path check for ZONE_DEVICE pfns in an online section. In > the fast path online_section() for a full ZONE_DEVICE section returns > false. > > Because the collision case is rare, and for simplicity, the > SECTION_TAINT_ZONE_DEVICE flag is never cleared once set. > > Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") > Cc: Andrew Morton > Reported-by: Michal Hocko > Reported-by: David Hildenbrand > Signed-off-by: Dan Williams > --- > include/linux/mmzone.h | 22 +++++++++++++++------- > mm/memory_hotplug.c | 38 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 53 insertions(+), 7 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index b593316bff3d..0b5c44f730b4 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1273,13 +1273,14 @@ extern size_t mem_section_usage_size(void); > * which results in PFN_SECTION_SHIFT equal 6. > * To sum it up, at least 6 bits are available. > */ > -#define SECTION_MARKED_PRESENT (1UL<<0) > -#define SECTION_HAS_MEM_MAP (1UL<<1) > -#define SECTION_IS_ONLINE (1UL<<2) > -#define SECTION_IS_EARLY (1UL<<3) > -#define SECTION_MAP_LAST_BIT (1UL<<4) > -#define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > -#define SECTION_NID_SHIFT 3 > +#define SECTION_MARKED_PRESENT (1UL<<0) > +#define SECTION_HAS_MEM_MAP (1UL<<1) > +#define SECTION_IS_ONLINE (1UL<<2) > +#define SECTION_IS_EARLY (1UL<<3) > +#define SECTION_TAINT_ZONE_DEVICE (1UL<<4) > +#define SECTION_MAP_LAST_BIT (1UL<<5) > +#define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > +#define SECTION_NID_SHIFT 3 > > static inline struct page *__section_mem_map_addr(struct mem_section *section) > { > @@ -1318,6 +1319,13 @@ static inline int online_section(struct mem_section *section) > return (section && (section->section_mem_map & SECTION_IS_ONLINE)); > } > > +static inline int online_device_section(struct mem_section *section) > +{ > + unsigned long flags = SECTION_IS_ONLINE | SECTION_TAINT_ZONE_DEVICE; > + > + return section && ((section->section_mem_map & flags) == flags); > +} > + > static inline int online_section_nr(unsigned long nr) > { > return online_section(__nr_to_section(nr)); > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index a845b3979bc0..b2ccb84c3082 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -308,6 +308,7 @@ static int check_hotplug_memory_addressable(unsigned long pfn, > struct page *pfn_to_online_page(unsigned long pfn) > { > unsigned long nr = pfn_to_section_nr(pfn); > + struct dev_pagemap *pgmap; > struct mem_section *ms; > > if (nr >= NR_MEM_SECTIONS) > @@ -320,6 +321,22 @@ struct page *pfn_to_online_page(unsigned long pfn) > if (!pfn_section_valid(ms, pfn)) > return NULL; > > + if (!online_device_section(ms)) > + return pfn_to_page(pfn); > + > + /* > + * Slowpath: when ZONE_DEVICE collides with > + * ZONE_{NORMAL,MOVABLE} within the same section some pfns in > + * the section may be 'offline' but 'valid'. Only > + * get_dev_pagemap() can determine sub-section online status. > + */ > + pgmap = get_dev_pagemap(pfn, NULL); > + put_dev_pagemap(pgmap); > + > + /* The presence of a pgmap indicates ZONE_DEVICE offline pfn */ > + if (pgmap) > + return NULL; > + > return pfn_to_page(pfn); > } > EXPORT_SYMBOL_GPL(pfn_to_online_page); > @@ -702,6 +719,14 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon > pgdat->node_spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - pgdat->node_start_pfn; > > } > + > +static void section_taint_zone_device(unsigned long pfn) > +{ > + struct mem_section *ms = __pfn_to_section(pfn); > + > + ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE; > +} > + > /* > * Associate the pfn range with the given zone, initializing the memmaps > * and resizing the pgdat/zone data to span the added pages. After this > @@ -731,6 +756,19 @@ void __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, > resize_pgdat_range(pgdat, start_pfn, nr_pages); > pgdat_resize_unlock(pgdat, &flags); > > + /* > + * Subsection population requires care in pfn_to_online_page(). > + * Set the taint to enable the slow path detection of > + * ZONE_DEVICE pages in an otherwise ZONE_{NORMAL,MOVABLE} > + * section. > + */ > + if (zone_idx(zone) == ZONE_DEVICE) { > + if (!IS_ALIGNED(start_pfn, PAGES_PER_SECTION)) > + section_taint_zone_device(start_pfn); > + if (!IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)) > + section_taint_zone_device(start_pfn + nr_pages); > + } > + > /* > * TODO now we have a visible range of pages which are not associated > * with their zone properly. Not nice but set_pfnblock_flags_mask > LGHTM, thanks Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb