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

From: David Vrabel
Date: Fri Jan 24 2014 - 06:05:32 EST

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On 23/01/14 16:23, Elena Ufimtseva wrote:
> On Wed, Jan 22, 2014 at 3:33 PM, Steven Noonan <steven@xxxxxxxxxxxxxx> wrote:
>> On Wed, Jan 22, 2014 at 03:18:50PM -0500, Elena Ufimtseva wrote:
>>> 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?
>
> It does use _PAGE_GLOBAL for guest user pages
>
>>>>>>
>>>>>> 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.
>>
>> Nope:
>>
>> # cat /proc/cmdline
>> root=/dev/xvda1 ro rootwait rootfstype=ext4 nomodeset console=hvc0 earlyprintk=xen,verbose loglevel=7
>
>>
>>>
>>>>
>>>>
>>>> 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
>
> I was able to reproduce this consistently, also with the latest mm
> patches from yesterday.
> Can you please try this:
>
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index ce563be..76dcf96 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -365,7 +365,7 @@ void xen_ptep_modify_prot_commit(struct mm_struct
> *mm, unsigned long addr,
> /* Assume pteval_t is equivalent to all the other *val_t types. */
> static pteval_t pte_mfn_to_pfn(pteval_t val)
> {
> - if (val & _PAGE_PRESENT) {
> + if ((val & _PAGE_PRESENT) || ((val &
> (_PAGE_NUMA|_PAGE_PRESENT)) == _PAGE_NUMA)) {

if (val & (_PAGE_PRESENT | _PAGE_NUMA))

is equivalent.

David
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Next message: Tomi Valkeinen: "[GIT PULL] fbdev changes for 3.14"
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