Re: copy_huge_page: unable to handle kernel NULL pointer dereference at 0000000000000008

[Andrey Korolyov <andrey@xdel.ru>]

On Tue, Feb 24, 2015 at 3:12 AM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
> On Wed, Feb 04, 2015 at 08:34:04PM +0400, Andrey Korolyov wrote:
>> >Hi,
>> >
>> >I've seen the problem quite a few times.  Before spending more time on
>> >it, I'd like to have a quick check here to see if anyone ever saw the
>> >same problem?  Hope it is a relevant question with this mail list.
>> >
>> >
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.078623] BUG: unable to handle
>> >kernel NULL pointer dereference at 0000000000000008
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.078916] IP: [<ffffffff8118d0fa>]
>> >copy_huge_page+0x8a/0x2a0
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.079128] PGD 0
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.079198] Oops: 0000 [#1] SMP
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.079319] Modules linked in:
>> >ip6table_filter ip6_tables ebtable_nat ebtables ipt_MASQUERADE
>> >iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
>> >xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp
>> >iptable_filter ip_tables x_tables kvm_intel kvm bridge stp llc ast ttm
>> >drm_kms_helper drm sysimgblt sysfillrect syscopyarea lp mei_me ioatdma
>> >ext2 parport mei shpchp dcdbas joydev mac_hid lpc_ich acpi_pad wmi
>> >hid_generic usbhid hid ixgbe igb dca i2c_algo_bit ahci ptp libahci
>> >mdio pps_core
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.081090] CPU: 19 PID: 3494 Comm:
>> >qemu-system-x86 Not tainted 3.11.0-15-generic #25~precise1-Ubuntu
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.081424] Hardware name: Dell Inc.
>> >PowerEdge C6220 II/09N44V, BIOS 2.0.3 07/03/2013
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.081705] task: ffff881026750000
>> >ti: ffff881026056000 task.ti: ffff881026056000
>> >Jul  2 11:08:21 arno-3 kernel: [ 2165.081973] RIP:
>> >0010:[<ffffffff8118d0fa>]  [<ffffffff8118d0fa>]
>> >copy_huge_page+0x8a/0x2a0
>>
>>
>> Hello,
>>
>> sorry for possible top-posting, the same issue appears on at least
>> 3.10 LTS series. The original thread is at
>> http://marc.info/?l=kvm&m=14043742300901.
>
> Andrey,
>
> I am unable to access the URL above?
>
>> The necessary components for failure to reappear are a single running
>> kvm guest and mounted large thp: hugepagesz=1G (seemingly the same as
>> in initial report). With default 2M pages everything is working well,
>> the same for 3.18 with 1G THP. Are there any obvious clues for the
>> issue?
>>
>> Thanks!
>
>

Hello,

Marcelo, sorry, I`ve missed your reply in time. The working link, for
example is http://www.spinics.net/lists/linux-mm/msg75658.html. The
reproducer is a very simple, you need 1G THP and mounted hugetlbfs.
What is interesting, if guest is backed by THP like '-object
memory-backend-file,id=mem,size=1G,mem-path=/hugepages,share=on' the
failure is less likely to occur.

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