Re: [Xen-devel] [BISECTED] Linux 3.12.7 introduces page map handling regression

[Elena Ufimtseva <ufimtseva@xxxxxxxxx>]

On Wed, Jan 22, 2014 at 9:29 AM, Daniel Borkmann <borkmann@xxxxxxxxxxxxx> wrote:
> On 01/22/2014 08:29 AM, Steven Noonan wrote:
>>
>> On Wed, Jan 22, 2014 at 12:02:15AM -0500, Konrad Rzeszutek Wilk wrote:
>>>
>>> On Tue, Jan 21, 2014 at 07:20:45PM -0800, Steven Noonan wrote:
>>>>
>>>> On Tue, Jan 21, 2014 at 06:47:07PM -0800, Linus Torvalds wrote:
>>>>>
>>>>> On Tue, Jan 21, 2014 at 5:49 PM, Greg Kroah-Hartman
>>>>> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>>
>>> Adding extra folks to the party.
>>>>>>
>>>>>>
>>>>>> Odds are this also shows up in 3.13, right?
>>>>
>>>>
>>>> Reproduced using 3.13 on the PV guest:
>>>>
>>>>         [  368.756763] BUG: Bad page map in process mp
>>>> pte:80000004a67c6165 pmd:e9b706067
>>>>         [  368.756777] page:ffffea001299f180 count:0 mapcount:-1
>>>> mapping:          (null) index:0x0
>>>>         [  368.756781] page flags: 0x2fffff80000014(referenced|dirty)
>>>>         [  368.756786] addr:00007fd1388b7000 vm_flags:00100071
>>>> anon_vma:ffff880e9ba15f80 mapping:          (null) index:7fd1388b7
>>>>         [  368.756792] CPU: 29 PID: 618 Comm: mp Not tainted 3.13.0-ec2
>>>> #1
>>>>         [  368.756795]  ffff880e9b718958 ffff880e9eaf3cc0
>>>> ffffffff814d8748 00007fd1388b7000
>>>>         [  368.756803]  ffff880e9eaf3d08 ffffffff8116d289
>>>> 0000000000000000 0000000000000000
>>>>         [  368.756809]  ffff880e9b7065b8 ffffea001299f180
>>>> 00007fd1388b8000 ffff880e9eaf3e30
>>>>         [  368.756815] Call Trace:
>>>>         [  368.756825]  [<ffffffff814d8748>] dump_stack+0x45/0x56
>>>>         [  368.756833]  [<ffffffff8116d289>] print_bad_pte+0x229/0x250
>>>>         [  368.756837]  [<ffffffff8116eae3>]
>>>> unmap_single_vma+0x583/0x890
>>>>         [  368.756842]  [<ffffffff8116feb5>] unmap_vmas+0x65/0x90
>>>>         [  368.756847]  [<ffffffff81175dac>] unmap_region+0xac/0x120
>>>>         [  368.756852]  [<ffffffff81176379>] ? vma_rb_erase+0x1c9/0x210
>>>>         [  368.756856]  [<ffffffff81177f10>] do_munmap+0x280/0x370
>>>>         [  368.756860]  [<ffffffff81178041>] vm_munmap+0x41/0x60
>>>>         [  368.756864]  [<ffffffff81178f32>] SyS_munmap+0x22/0x30
>>>>         [  368.756869]  [<ffffffff814e70ed>]
>>>> system_call_fastpath+0x1a/0x1f
>>>>         [  368.756872] Disabling lock debugging due to kernel taint
>>>>         [  368.760084] BUG: Bad rss-counter state mm:ffff880e9d079680
>>>> idx:0 val:-1
>>>>         [  368.760091] BUG: Bad rss-counter state mm:ffff880e9d079680
>>>> idx:1 val:1
>>>>
>>>>>
>>>>> Probably. I don't have a Xen PV setup to test with (and very little
>>>>> interest in setting one up).. And I have a suspicion that it might not
>>>>> be so much about Xen PV, as perhaps about the kind of hardware.
>>>>>
>>>>> I suspect the issue has something to do with the magic _PAGE_NUMA
>>>>> tie-in with _PAGE_PRESENT. And then mprotect(PROT_NONE) ends up
>>>>> removing the _PAGE_PRESENT bit, and now the crazy numa code is
>>>>> confused.
>>>>>
>>>>> The whole _PAGE_NUMA thing is a f*cking horrible hack, and shares the
>>>>> bit with _PAGE_PROTNONE, which is why it then has that tie-in to
>>>>> _PAGE_PRESENT.
>>>>>
>>>>> Adding Andrea to the Cc, because he's the author of that horridness.
>>>>> Putting Steven's test-case here as an attachement for Andrea, maybe
>>>>> that makes him go "Ahh, yes, silly case".
>>>>>
>>>>> Also added Kirill, because he was involved the last _PAGE_NUMA debacle.
>>>>>
>>>>> Andrea, you can find the thread on lkml, but it boils down to commit
>>>>> 1667918b6483 (backported to 3.12.7 as 3d792d616ba4) breaking the
>>>>> attached test-case (but apparently only under Xen PV). There it
>>>>> apparently causes a "BUG: Bad page map .." error.
>>>
>>>
>>> I *think* it is due to the fact that pmd_numa and pte_numa is getting the
>>> _raw_
>>> value of PMDs and PTEs. That is - it does not use the pvops interface
>>> and instead reads the values directly from the page-table. Since the
>>> page-table is also manipulated by the hypervisor - there are certain
>>> flags it also sets to do its business. It might be that it uses
>>> _PAGE_GLOBAL as well - and Linux picks up on that. If it was using
>>> pte_flags that would invoke the pvops interface.
>>>
>>> Elena, Dariof and George, you guys had been looking at this a bit deeper
>>> than I have. Does the Xen hypervisor use the _PAGE_GLOBAL for PV guests?
>>>
>>> This not-compiled-totally-bad-patch might shed some light on what I was
>>> thinking _could_ fix this issue - and IS NOT A FIX - JUST A HACK.
>>> It does not fix it for PMDs naturally (as there are no PMD paravirt ops
>>> for that).
>>
>>
>> Unfortunately the Totally Bad Patch seems to make no difference. I am
>> still able to repro the issue:

Steven, do you use numa=fake on boot cmd line for pv guest?

I had similar issue on pv guest. Let me check if the fix that resolved
this for me will help with 3.13.


>
>
> Maybe this one is also related to this BUG here (cc'ed people investigating
> this one) ...
>
>   https://lkml.org/lkml/2014/1/10/427
>
> ... not sure, though.
>
>
>>         [  346.374929] BUG: Bad page map in process mp
>> pte:80000004ae928065 pmd:e993f9067
>>         [  346.374942] page:ffffea0012ba4a00 count:0 mapcount:-1 mapping:
>> (null) index:0x0
>>         [  346.374946] page flags: 0x2fffff80000014(referenced|dirty)
>>         [  346.374951] addr:00007f06a9bbb000 vm_flags:00100071
>> anon_vma:ffff880e9939fe00 mapping:          (null) index:7f06a9bbb
>>         [  346.374956] CPU: 29 PID: 609 Comm: mp Not tainted 3.13.0-ec2+
>> #1
>>         [  346.374960]  ffff880e9cc38da8 ffff880e991a3cc0 ffffffff814d8768
>> 00007f06a9bbb000
>>         [  346.374967]  ffff880e991a3d08 ffffffff8116d289 0000000000000000
>> 0000000000000000
>>         [  346.374972]  ffff880e993f9dd8 ffffea0012ba4a00 00007f06a9bbc000
>> ffff880e991a3e30
>>         [  346.374979] Call Trace:
>>         [  346.374988]  [<ffffffff814d8768>] dump_stack+0x45/0x56
>>         [  346.374996]  [<ffffffff8116d289>] print_bad_pte+0x229/0x250
>>         [  346.375000]  [<ffffffff8116eae3>] unmap_single_vma+0x583/0x890
>>         [  346.375006]  [<ffffffff8116feb5>] unmap_vmas+0x65/0x90
>>         [  346.375011]  [<ffffffff81175dbc>] unmap_region+0xac/0x120
>>         [  346.375016]  [<ffffffff81176389>] ? vma_rb_erase+0x1c9/0x210
>>         [  346.375021]  [<ffffffff81177f20>] do_munmap+0x280/0x370
>>         [  346.375025]  [<ffffffff81178051>] vm_munmap+0x41/0x60
>>         [  346.375029]  [<ffffffff81178f42>] SyS_munmap+0x22/0x30
>>         [  346.375034]  [<ffffffff814e712d>]
>> system_call_fastpath+0x1a/0x1f
>>         [  346.375037] Disabling lock debugging due to kernel taint
>>         [  346.380082] BUG: Bad rss-counter state mm:ffff880e9d22bc00
>> idx:0 val:-1
>>         [  346.380088] BUG: Bad rss-counter state mm:ffff880e9d22bc00
>> idx:1 val:1
>>
>> This dump doesn't look dramatically different, either.
>>
>>>
>>> The other question is - how is AutoNUMA running when it is not enabled?
>>> Shouldn't those _PAGE_NUMA ops be nops when AutoNUMA hasn't even been
>>> turned on?
>>
>>
>> Well, NUMA_BALANCING is enabled in the kernel config[1], but I presume you
>> mean not enabled at runtime?
>>
>> [1]
>> http://git.uplinklabs.net/snoonan/projects/archlinux/ec2/ec2-packages.git/tree/linux-ec2/config.x86_64



-- 
Elena

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel