From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id E702D6B0038 for ; Thu, 21 Sep 2017 01:40:39 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id r74so4748915wme.5 for ; Wed, 20 Sep 2017 22:40:39 -0700 (PDT) Received: from youngberry.canonical.com (youngberry.canonical.com. [91.189.89.112]) by mx.google.com with ESMTPS id o26si361360edf.511.2017.09.20.22.40.37 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 20 Sep 2017 22:40:38 -0700 (PDT) Received: from mail-io0-f199.google.com ([209.85.223.199]) by youngberry.canonical.com with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1duuE1-00064y-Bm for linux-mm@kvack.org; Thu, 21 Sep 2017 05:40:37 +0000 Received: by mail-io0-f199.google.com with SMTP id 93so8482505iol.2 for ; Wed, 20 Sep 2017 22:40:37 -0700 (PDT) Date: Thu, 21 Sep 2017 00:40:34 -0500 From: Seth Forshee Subject: Re: Memory hotplug regression in 4.13 Message-ID: <20170921054034.judv6ovyg5yks4na@ubuntu-hedt> References: <20170919164114.f4ef6oi3yhhjwkqy@ubuntu-xps13> <20170920092931.m2ouxfoy62wr65ld@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170920092931.m2ouxfoy62wr65ld@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, Sep 20, 2017 at 11:29:31AM +0200, Michal Hocko wrote: > Hi, > I am currently at a conference so I will most probably get to this next > week but I will try to ASAP. > > On Tue 19-09-17 11:41:14, Seth Forshee wrote: > > Hi Michal, > > > > I'm seeing oopses in various locations when hotplugging memory in an x86 > > vm while running a 32-bit kernel. The config I'm using is attached. To > > reproduce I'm using kvm with the memory options "-m > > size=512M,slots=3,maxmem=2G". Then in the qemu monitor I run: > > > > object_add memory-backend-ram,id=mem1,size=512M > > device_add pc-dimm,id=dimm1,memdev=mem1 > > > > Not long after that I'll see an oops, not always in the same location > > but most often in wp_page_copy, like this one: > > This is rather surprising. How do you online the memory? The kernel has CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y. > > [ 24.673623] BUG: unable to handle kernel paging request at dffff000 > > [ 24.675569] IP: wp_page_copy+0xa8/0x660 > > could you resolve the IP into the source line? It seems I don't have that kernel anymore, but I've got a 4.14-rc1 build and the problem still occurs there. It's pointing to the call to __builtin_memcpy in memcpy (include/linux/string.h line 340), which we get to via wp_page_copy -> cow_user_page -> copy_user_highpage. Thanks, Seth -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org