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[37.188.130.62]) by smtp.gmail.com with ESMTPSA id b191sm6667198wmd.39.2020.04.16.23.38.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Apr 2020 23:38:08 -0700 (PDT) Date: Fri, 17 Apr 2020 08:38:07 +0200 From: Michal Hocko To: Vishal Verma Cc: linux-mm@kvack.org, linux-nvdimm@lists.01.org, David Hildenbrand , Dan Williams , Dave Hansen Subject: Re: [PATCH v5] mm/memory_hotplug: refrain from adding memory into an impossible node Message-ID: <20200417063807.GE26707@dhcp22.suse.cz> References: <20200416225438.15208-1-vishal.l.verma@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200416225438.15208-1-vishal.l.verma@intel.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 Thu 16-04-20 16:54:38, Vishal Verma wrote: > A misbehaving qemu created a situation where the ACPI SRAT table > advertised one fewer proximity domains than intended. The NFIT table did > describe all the expected proximity domains. This caused the device dax > driver to assign an impossible target_node to the device, and when > hotplugged as system memory, this would fail with the following > signature: > > [ +0.001627] BUG: kernel NULL pointer dereference, address: 0000000000000088 > [ +0.001331] #PF: supervisor read access in kernel mode > [ +0.000975] #PF: error_code(0x0000) - not-present page > [ +0.000976] PGD 80000001767d4067 P4D 80000001767d4067 PUD 10e0c4067 PMD 0 > [ +0.001338] Oops: 0000 [#1] SMP PTI > [ +0.000676] CPU: 4 PID: 22737 Comm: kswapd3 Tainted: G O 5.6.0-rc5 #9 > [ +0.001457] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > [ +0.001990] RIP: 0010:prepare_kswapd_sleep+0x7c/0xc0 > [ +0.000780] Code: 89 df e8 87 fd ff ff 89 c2 31 c0 84 d2 74 e6 0f 1f 44 > 00 00 48 8b 05 fb af 7a 01 48 63 93 88 1d 01 00 48 8b > 84 d0 20 0f 00 00 <48> 3b 98 88 00 00 00 75 28 f0 80 a0 > 80 00 00 00 fe f0 80 a3 38 20 > [ +0.002877] RSP: 0018:ffffc900017a3e78 EFLAGS: 00010202 > [ +0.000805] RAX: 0000000000000000 RBX: ffff8881209e0000 RCX: 0000000000000000 > [ +0.001115] RDX: 0000000000000003 RSI: 0000000000000000 RDI: ffff8881209e0e80 > [ +0.001098] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000008000 > [ +0.001092] R10: 0000000000000000 R11: 0000000000000003 R12: 0000000000000003 > [ +0.001092] R13: 0000000000000003 R14: 0000000000000000 R15: ffffc900017a3ec8 > [ +0.001091] FS: 0000000000000000(0000) GS:ffff888318c00000(0000) knlGS:0000000000000000 > [ +0.001275] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ +0.000882] CR2: 0000000000000088 CR3: 0000000120b50002 CR4: 00000000001606e0 > [ +0.001095] Call Trace: > [ +0.000388] kswapd+0x103/0x520 > [ +0.000494] ? finish_wait+0x80/0x80 > [ +0.000547] ? balance_pgdat+0x5a0/0x5a0 > [ +0.000607] kthread+0x120/0x140 > [ +0.000508] ? kthread_create_on_node+0x60/0x60 > [ +0.000706] ret_from_fork+0x3a/0x50 > > Add a check in the add_memory path to fail if the node to which we > are adding memory is in the node_possible_map > > Cc: Michal Hocko > Cc: David Hildenbrand > Cc: Dan Williams > Cc: Dave Hansen > Acked-by: David Hildenbrand > Signed-off-by: Vishal Verma Acked-by: Michal Hocko We can start thiking on how to handle such a misconfiguration more gracefully when we see this hitting in real world and find out more why that happens. E.g. if a FW/BIOS are not fixable then we can implement some fallback strategy but this should be a good start. Thanks! > --- > mm/memory_hotplug.c | 5 +++++ > 1 file changed, 5 insertions(+) > > v2: > - Centralize the check in the add_memory path (David) > - Instead of failing, add the memory to a nearby node, while warning > (and tainting) to call out attention to the firmware bug (Dan) > > v3: > - Fix the CONFIG_NUMA=n case, and use node 0 as the final fallback (Dan) > > v4: > - Error out instead of being smart about picking a node that wasn't > asked for (Michal) > > v5: > - Change the return code to -EINVAL (David) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 0a54ffac8c68..e07b80d149db 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1005,6 +1005,11 @@ int __ref add_memory_resource(int nid, struct resource *res) > if (ret) > return ret; > > + if (!node_possible(nid)) { > + WARN(1, "node %d was absent from the node_possible_map\n", nid); > + return -EINVAL; > + } > + > mem_hotplug_begin(); > > /* > -- > 2.21.1 -- Michal Hocko SUSE Labs