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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,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 20E3DC433E1 for ; Thu, 28 May 2020 09:08:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CBAD020B80 for ; Thu, 28 May 2020 09:08:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="e7xAluTr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBAD020B80 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 63E8C800B6; Thu, 28 May 2020 05:08:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5C83F80010; Thu, 28 May 2020 05:08:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 49008800B6; Thu, 28 May 2020 05:08:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id 2ED5280010 for ; Thu, 28 May 2020 05:08:39 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id EA5489096 for ; Thu, 28 May 2020 09:08:38 +0000 (UTC) X-FDA: 76865552316.25.swim56_85a5eafa8b360 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id CB2711804E3A1 for ; Thu, 28 May 2020 09:08:38 +0000 (UTC) X-HE-Tag: swim56_85a5eafa8b360 X-Filterd-Recvd-Size: 11467 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Thu, 28 May 2020 09:08:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590656917; 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=nqBqr33l4NNMWZMOBpKdAAmzF/g/ZipZWnHqU2+36DA=; b=e7xAluTroxiKZV1ggFjQc6sdLDD5/ZVBMUkl3FaB8c7/pSVPCMSztx2T0B/nKaU2OlaZ+o T0ZHdcE573fGLkjfwxKLbNFdYZrZZ2f9FoVcpLu+9/oHnLsQ6AZ867HgXThUMkAbZHvC31 Zeuy0YK/OWXcPN06EX2UfHdccz06ynU= 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-496-cIcsi-DGMjuMB1DMzAxkKA-1; Thu, 28 May 2020 05:08:35 -0400 X-MC-Unique: cIcsi-DGMjuMB1DMzAxkKA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BFC63474; Thu, 28 May 2020 09:08:34 +0000 (UTC) Received: from localhost (ovpn-12-80.pek2.redhat.com [10.72.12.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E4BEE19D71; Thu, 28 May 2020 09:08:30 +0000 (UTC) Date: Thu, 28 May 2020 17:08:28 +0800 From: Baoquan He To: David Hildenbrand , rppt@linux.ibm.com Cc: mgorman@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/compaction: Fix the incorrect hole in fast_isolate_freepages() Message-ID: <20200528090828.GA22153@MiWiFi-R3L-srv> References: <20200528085933.GH20045@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200528085933.GH20045@MiWiFi-R3L-srv> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Rspamd-Queue-Id: CB2711804E3A1 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 05/28/20 at 04:59pm, Baoquan He wrote: > akpm@linux-foundation.org, cai@lca.pw, mhocko@kernel.org, steve.wahl@hpe.com, > Bcc: bhe@redhat.com > Subject: Re: [PATCH] mm/compaction: Fix the incorrect hole in > fast_isolate_freepages() > Reply-To: > In-Reply-To: <01beec81-565f-d335-5eff-22693fc09c0e@redhat.com> Sorry, mail client mess up the mail header, have resent one. Please ignore this one. > > On 05/26/20 at 01:49pm, David Hildenbrand wrote: > > On 26.05.20 13:32, Mike Rapoport wrote: > > > Hello Baoquan, > > > > > > On Tue, May 26, 2020 at 04:45:43PM +0800, Baoquan He wrote: > > >> On 05/22/20 at 05:20pm, Mike Rapoport wrote: > > >>> Hello Baoquan, > > >>> > > >>> On Fri, May 22, 2020 at 03:25:24PM +0800, Baoquan He wrote: > > >>>> On 05/22/20 at 03:01pm, Baoquan He wrote: > > >>>>> > > >>>>> So let's add these unavailable ranges into memblock and reserve them > > >>>>> in init_unavailable_range() instead. With this change, they will be added > > >>>>> into appropriate node and zone in memmap_init(), and initialized in > > >>>>> reserve_bootmem_region() just like any other memblock reserved regions. > > >>>> > > >>>> Seems this is not right. They can't get nid in init_unavailable_range(). > > >>>> Adding e820 ranges may let them get nid. But the hole range won't be > > >>>> added to memblock, and still has the issue. > > >>>> > > >>>> Nack this one for now, still considering. > > >>> > > >>> Why won't we add the e820 reserved ranges to memblock.memory during > > >>> early boot as I suggested? > > >>> > > >>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > > >>> index c5399e80c59c..b0940c618ed9 100644 > > >>> --- a/arch/x86/kernel/e820.c > > >>> +++ b/arch/x86/kernel/e820.c > > >>> @@ -1301,8 +1301,11 @@ void __init e820__memblock_setup(void) > > >>> if (end != (resource_size_t)end) > > >>> continue; > > >>> > > >>> - if (entry->type == E820_TYPE_SOFT_RESERVED) > > >>> + if (entry->type == E820_TYPE_SOFT_RESERVED || > > >>> + entry->type == E820_TYPE_RESERVED) { > > >>> + memblock_add(entry->addr, entry->size); > > >>> memblock_reserve(entry->addr, entry->size); > > >>> + } > > >>> > > >>> if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN) > > >>> continue; > > >>> > > >>> The setting of node later in numa_init() will assign the proper node > > >>> for these regions as it does for the usable memory. > > >> > > >> Yes, if it's only related to e820 reserved region, this truly works. > > >> > > >> However, it also has ACPI table regions. That's why I changed to call > > >> the problematic area as firmware reserved ranges later. > > >> > > >> Bisides, you can see below line, there's another reserved region which only > > >> occupies one page in one memory seciton. If adding to memblock.memory, we also > > >> will build struct mem_section and the relevant struct pages for the whole > > >> section. And then the holes around that page will be added and initialized in > > >> init_unavailable_mem(). numa_init() will assign proper node for memblock.memory > > >> and memblock.reserved, but won't assign proper node for the holes. > > >> > > >> ~~~ > > >> [ 0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed80fff] reserved > > >> ~~~ > > >> > > >> So I still think we should not add firmware reserved range into > > >> memblock for fixing this issue. > > >> > > >> And, the fix in the original patch seems necessary. You can see in > > >> compaction code, the migration source is chosen from LRU pages or > > >> movable pages, the migration target has to be got from Buddy. However, > > >> only the min_pfn in fast_isolate_freepages(), it's calculated by > > >> distance between cc->free_pfn - cc->migrate_pfn, we can't guarantee it's > > >> safe, then use it as the target to handle. > > > > > > I do not object to your original fix with careful check for pfn validity. > > > > > > But I still think that the memory reserved by the firmware is still > > > memory and it should be added to memblock.memory. This way the memory > > > > If it's really memory that could be read/written, I think I agree. > > I would say some of them may not be allowed to be read/written, if I > understand it correctly. I roughly went through the x86 init code, there > are some places where mem region is marked as E820_TYPE_RESERVED so that > they are not touched after initialization. E.g: > > 1) pfn 0 > In trim_bios_range(), we set the pfn 0 as E820_TYPE_RESERVED. You can > see the code comment, this is a BIOS owned area, but not kernel RAM. > > 2)GART reserved region > In early_gart_iommu_check(), GART IOMMU firmware will reserve a region > in an area, firmware designer won't map system RAM into that area. > > And also intel_graphics_stolen(), arch_rmrr_sanity_check(), these > regions are not system RAM backed area, reading from or writting into > these area may cause error. > > Futhermore, there's a KASLR bug found by HPE, its triggering and root > cause are written into below commit log. You can see that accessing to > firmware reserved region caused BIOS to halt system when cpu doing > speculative. > > commit 2aa85f246c181b1fa89f27e8e20c5636426be624 > Author: Steve Wahl > Date: Tue Sep 24 16:03:55 2019 -0500 > > x86/boot/64: Make level2_kernel_pgt pages invalid outside kernel area > > Our hardware (UV aka Superdome Flex) has address ranges marked > reserved by the BIOS. Access to these ranges is caught as an error, > causing the BIOS to halt the system. > > > > > > map will be properly initialized from the very beginning and we won't > > > need init_unavailable_mem() and alike workarounds and. Obviously, the patch > > > > I remember init_unavailable_mem() is necessary for holes within > > sections, where we actually *don't* have memory, but we still have have > > a valid memmap (full section) that we have to initialize. > > > > See the example from 4b094b7851bf ("mm/page_alloc.c: initialize memmap > > of unavailable memory directly"). Our main memory ends within a section, > > so we have to initialize the remaining parts because the whole section > > will be marked valid/online. > > Yes, memory hole need be handled in init_unavailable_mem(). Since we > have created struct page for them, need initialize them. We can't > discard init_unavailable_mem() for now. > > > > > Any way to improve this handling is appreciated. In that patch I also > > spelled out that we might want to mark such holes via a new page type, > > e.g., PageHole(). Such a page is a memory hole, but has a valid memmap. > > Any content in the memmap (zone/node) should be ignored. > > As I said at above, I am a little conservative to add all those regions of > E820_TYPE_RESERVED into memblock.memory and memblock.reserved, because > most of them are firmware reserved region, they may be not backed by normal > RAM. > > I was thinking to step back to use mm_zero_struct_page() inside > init_unavailable_range() as below. But it doesn't differ much > from __init_single_page(), except of the _refcount and mapcount. > Zeroing struct page equals to putting them into node 0, zero 0. > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3973b5fdfe3f..4e4b72cf5283 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6901,7 +6901,7 @@ static u64 __init init_unavailable_range(unsigned long spfn, unsigned long epfn) > * (in memblock.reserved but not in memblock.memory) will > * get re-initialized via reserve_bootmem_region() later. > */ > - __init_single_page(pfn_to_page(pfn), pfn, 0, 0); > + mm_zero_struct_page(pfn_to_page(pfn)); > __SetPageReserved(pfn_to_page(pfn)); > pgcnt++; > } > > About adding these unavailable ranges into node/zone, in the old code, > it just happened to add them into expected node/zone. You can see in > early_pfn_in_nid(), if no nid found from memblock, the returned '-1' > will make it true ironically. But that is not saying the bad thing > always got good result. If the last zone of node 0 is DMA32 zone, the > deferred init will skip the only chance to add some of unavailable > rnages into expected node/zone. Means they were not always added into > appropriate node/zone before, the change of iterating memblock.memory in > memmap_init() dones't introduce regression. > > static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node) > { > int nid; > > nid = __early_pfn_to_nid(pfn, &early_pfnnid_cache); > if (nid >= 0 && nid != node) > return false; > return true; > } > > So if no anybody need access them after boot, not adding them into any > node/zone sounds better. Otherwise, better add them in the appropriate > node/zone. > > > > > But it's all quite confusing, especially across architectures and ... > > > > > above is not enough, but it's a small step in this direction. > > > > > > I believe that improving the early memory initialization would make many > > > things simpler and more robust, but that's a different story :) > > > > ... I second that. > > > > -- > > Thanks, > > > > David / dhildenb > >