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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY 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 EBBDCC433E0 for ; Wed, 24 Jun 2020 08:13:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B8D9C20738 for ; Wed, 24 Jun 2020 08:13:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B8D9C20738 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 314246B0003; Wed, 24 Jun 2020 04:13:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2C4DF6B0007; Wed, 24 Jun 2020 04:13:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1B33B6B0008; Wed, 24 Jun 2020 04:13:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id 04D416B0003 for ; Wed, 24 Jun 2020 04:13:31 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 89E212C84 for ; Wed, 24 Jun 2020 08:13:31 +0000 (UTC) X-FDA: 76963391022.14.crown18_550b91826e42 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id E0B071822987A for ; Wed, 24 Jun 2020 08:13:30 +0000 (UTC) X-HE-Tag: crown18_550b91826e42 X-Filterd-Recvd-Size: 4906 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Wed, 24 Jun 2020 08:13:28 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R531e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01358;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0U0aKfqF_1592986404; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U0aKfqF_1592986404) by smtp.aliyun-inc.com(127.0.0.1); Wed, 24 Jun 2020 16:13:24 +0800 Date: Wed, 24 Jun 2020 16:13:24 +0800 From: Wei Yang To: David Hildenbrand Cc: Michal Hocko , Wei Yang , akpm@linux-foundation.org, osalvador@suse.de, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/spase: never partially remove memmap for early section Message-ID: <20200624081324.GA12461@L-31X9LVDL-1304.local> Reply-To: Wei Yang References: <20200623094258.6705-1-richard.weiyang@linux.alibaba.com> <20200623151828.GA31426@dhcp22.suse.cz> <57d8a558-dcb3-b318-8e38-6c016b050414@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <57d8a558-dcb3-b318-8e38-6c016b050414@redhat.com> X-Rspamd-Queue-Id: E0B071822987A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 24, 2020 at 09:48:43AM +0200, David Hildenbrand wrote: >On 23.06.20 17:18, Michal Hocko wrote: >> On Tue 23-06-20 17:42:58, Wei Yang wrote: >>> For early sections, we assumes its memmap will never be partially >>> removed. But current behavior breaks this. >>> >>> Let's correct it. >>> >>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>> Signed-off-by: Wei Yang >> >> Can a user trigger this or is this a theoretical bug? > >I tried to reproduce it, but somehow I get unexpected behavior. >With a hacked QEMU I can get David, Thanks for your effort. Would you mind sharing your qemu command line, so that I can have a try at my side? > >$ cat /proc/iomem >[...] >100000000-143ffffff : System RAM >144000000-343dfffff : Persistent Memory > 144000000-1441fffff : namespace0.0 > 144200000-144ffffff : dax0.0 > >After >$ ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax --size=16M > >I get > >$ cat /proc/iomem >[...] >100000000-143ffffff : System RAM >144000000-343dfffff : Persistent Memory > 144000000-1441fffff : namespace0.0 > 144200000-144ffffff : dax0.0 > The memory layout seems not changed. >I can trigger remove+re-add via >$ ndctl create-namespace --force --reconfig=namespace0.0 --mode=devdax --size=16M Do we need to change the mode to force the reconfig? > >So we clearly have an overlap between System RAM and dax0.0 within a section. >However, I never get early_section() to trigger in >section_activate()/section_deactivate() ? That's unexpected > > >Definitely something seems to go wrong after the first "ndctl create-namespace". >Using a random page walker: > >[root@localhost ~]# ./page-types What is this page-types? >[ 387.019229] general protection fault, probably for non-canonical address 0xfdfdfdfdfdfdfdfc: 0000 [#1] SMP NOPTI >[ 387.020172] CPU: 17 PID: 1314 Comm: page-types Kdump: loaded Tainted: G W 5.8.0-rc2 #20 >[ 387.021015] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.4 >[ 387.022056] RIP: 0010:stable_page_flags+0x27/0x3f0 >[ 387.022519] Code: 00 00 00 66 66 66 66 90 48 85 ff 0f 84 d2 03 00 00 41 54 55 48 89 fd 53 48 8b 57 08 48 8b 1f 48f >[ 387.024291] RSP: 0018:ffff9f8781057e58 EFLAGS: 00010202 >[ 387.024775] RAX: fdfdfdfdfdfdfdfc RBX: fdfdfdfdfdfdfdfd RCX: 00007ffc4f4f1f78 >[ 387.025423] RDX: 0000000000000001 RSI: 0000002000000000 RDI: ffffc590c5100000 >[ 387.026052] RBP: ffffc590c5100000 R08: 0000000000000001 R09: 0000000000000000 >[ 387.026696] R10: 0000000000000000 R11: 0000000000000000 R12: 00007ffc4f4f1f80 >[ 387.027324] R13: 0000000000040000 R14: 00007ffc4f4d1f80 R15: ffffffffa1577ee0 >[ 387.027974] FS: 00007f91a0f9c580(0000) GS:ffff888b3f7c0000(0000) knlGS:0000000000000000 >[ 387.028699] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >[ 387.029223] CR2: 0000000000449b00 CR3: 000000007a7fc000 CR4: 00000000000006e0 >[ 387.029864] Call Trace: >[ 387.030108] kpageflags_read+0xcc/0x160 >[ 387.030473] proc_reg_read+0x53/0x80 >[ 387.030809] vfs_read+0x9d/0x150 >[ 387.031114] ksys_pread64+0x65/0xa0 >[ 387.031449] do_syscall_64+0x4d/0x90 >[ 387.031783] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me