Re: Memory hotplug regression in 4.13

Path	csiph.com!news.redatomik.org!aioe.org!bofh.it!news.nic.it!robomod
From	Seth Forshee <seth.forshee@canonical.com>
Newsgroups	linux.kernel
Subject	Re: Memory hotplug regression in 4.13
Date	Thu, 21 Sep 2017 07:50:02 +0200
Message-ID	<us2x4-55T-3@gated-at.bofh.it> (permalink)
References	<urtSF-7OZ-3@gated-at.bofh.it> <urJup-15w-13@gated-at.bofh.it>
X-Original-To	Michal Hocko <mhocko@kernel.org>
X-Google-Dkim-Signature	v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=/RDf+uuvRgj64nJ3GV9qJBeDgpDmC+hKYhF8a4vJDrA=; b=Cw/yNSEy+pGP2y4z2qOM9e+x3VXaSQlwUBpYrFAmolOTJZDBR3pg1JOsAFnO9M5U4i tWzbgrOpALH32VHpJcOLyNMGOEXKdxhfyhH/+sa6e000KlDJf1pOp6ND7orWPWFRq/9f 5xl77wCQPhAIRa//jBnoHcPwMcX86WeU5kYpgOpB57Y8dIYBp602IQLZCIt+9z24JRje 3gDBx3M69Ib+XZ8wry83ZWSVQ0hq5HxZVt1hYulAJxW63Um/jVql3T+sXjWo0v6wSWVo UpOSWzRfCj7TApp7IyDLsEZrxn+oMO4Hhv3K4BGPNUFytZ5INU0frJfVqz0ahuZqDNgA +yYQ==
X-Gm-Message-State	AHPjjUjCxfXSlz/y4ODE+Z4/ovSypV0my76NcQkmerV0bycQjepC7wFq 12aZ0EDf5CZJJz+72eic0hQUfh3paw+6n2k0A6dXAQtGz+rt7JWBl5nOkMeIVET3uDgu5fPS5bO +7I9MbLgIIQUsh8+TAjWNo0HN4il//bMR7Ufb7/7pOg==
X-Received	by 10.107.47.11 with SMTP id j11mr1571011ioo.217.1505972436364; Wed, 20 Sep 2017 22:40:36 -0700 (PDT)
X-Google-SMTP-Source	AOwi7QCWT75JaqBj7h3M4FN4gIDy34cX/2jQZZRIVELpKIAWSn/QygWnApzqQm+MVWzAsDrdBbpsqg==
X-Received	by 10.107.47.11 with SMTP id j11mr1571004ioo.217.1505972436118; Wed, 20 Sep 2017 22:40:36 -0700 (PDT)
MIME-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Disposition	inline
User-Agent	NeoMutt/20170609 (1.8.3)
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	35
Organization	linux.* mail to news gateway
X-Original-Cc	linux-mm@kvack.org, linux-kernel@vger.kernel.org
X-Original-Date	Thu, 21 Sep 2017 00:40:34 -0500
X-Original-Message-ID	<20170921054034.judv6ovyg5yks4na@ubuntu-hedt>
X-Original-References	<20170919164114.f4ef6oi3yhhjwkqy@ubuntu-xps13> <20170920092931.m2ouxfoy62wr65ld@dhcp22.suse.cz>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1736366

Show key headers only | View raw

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

Thread

Re: Memory hotplug regression in 4.13 Michal Hocko <mhocko@kernel.org> - 2017-09-20 11:30 +0200
  Re: Memory hotplug regression in 4.13 Seth Forshee <seth.forshee@canonical.com> - 2017-09-21 07:50 +0200
    Re: Memory hotplug regression in 4.13 Michal Hocko <mhocko@kernel.org> - 2017-09-25 15:00 +0200

csiph-web