Re: kernel bug in kvm_intel

[Andrew Theurer <habanero@linux.vnet.ibm.com>]

Avi Kivity wrote:
> On 10/30/2009 08:07 PM, Andrew Theurer wrote:
>>
>> I have finally bisected and isolated this to the following commit:
>>
>> ada3fa15057205b7d3f727bba5cd26b5912e350f
>> http://git.kernel.org/?p=virt/kvm/kvm.git;a=commit;h=ada3fa15057205b7d3f727bba5cd26b5912e350f 
>>
>>   
>>> Merge branch 'for-linus' of git://git./linux/kernel/git/tj/percpu
>>>
>>> * 'for-linus' of 
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (46 commits)
>>>    powerpc64: convert to dynamic percpu allocator
>>>    sparc64: use embedding percpu first chunk allocator
>>>    percpu: kill lpage first chunk allocator
>>>    x86,percpu: use embedding for 64bit NUMA and page for 32bit NUMA
>>>    percpu: update embedding first chunk allocator to handle sparse units
>>>    percpu: use group information to allocate vmap areas sparsely
>>>    vmalloc: implement pcpu_get_vm_areas()
>>>    vmalloc: separate out insert_vmalloc_vm()
>>>    percpu: add chunk->base_addr
>>>    percpu: add pcpu_unit_offsets[]
>>>    percpu: introduce pcpu_alloc_info and pcpu_group_info
>>>    percpu: move pcpu_lpage_build_unit_map() and 
>>> pcpul_lpage_dump_cfg() upward
>>>    percpu: add @align to pcpu_fc_alloc_fn_t
>>>    percpu: make @dyn_size mandatory for pcpu_setup_first_chunk()
>>>    percpu: drop @static_size from first chunk allocators
>>>    percpu: generalize first chunk allocator selection
>>>    percpu: build first chunk allocators selectively
>>>    percpu: rename 4k first chunk allocator to page
>>>    percpu: improve boot messages
>>>    percpu: fix pcpu_reclaim() locking
>>>      
>> The previous commit (5579fd7e6aed8860ea0c8e3f11897493153b10ad) does not
>> this problem.  FYI, this problem only occurs when oprofile is active.
>>
>> Any idea what in this commit might be the issue?
>>
>>    
> 
> 5579 is not the preceding commit, it is the merged branch:
> 
> commit ada3fa15057205b7d3f727bba5cd26b5912e350f
> Merge: 2f82af0 5579fd7
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Tue Sep 15 09:39:44 2009 -0700
> 
>     Merge branch 'for-linus' of 
> git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
> 
> 
> What happens with 2f82af0?
> 
2f82af0 is:

> Nicolas Pitre has a new email address
> 
> Due to problems at cam.org, my nico@cam.org email address is no longer
> valid.  FRom now on, nico@fluxnic.net should be used instead.

I have not tested that, but it doesn't seem likely that it would have 
anything to do with the problem.  Or maybe I am misunderstanding the 
impact of this commit?

FWIW, here is the bisect log:

git bisect start
# good: [227423904c709a8e60245c97081bbeb4fb500655] Merge branch 
'x86-pat-for-linus' of 
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
git bisect good 227423904c709a8e60245c97081bbeb4fb500655
# bad: [0f29f5871c165e346409f62d903f97cfad3894c5] Staging: rtl8192su: 
remove RTL8192SU ifdefs
git bisect bad 0f29f5871c165e346409f62d903f97cfad3894c5
# bad: [ada3fa15057205b7d3f727bba5cd26b5912e350f] Merge branch 
'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
git bisect bad ada3fa15057205b7d3f727bba5cd26b5912e350f
# bad: [ada3fa15057205b7d3f727bba5cd26b5912e350f] Merge branch 
'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
git bisect bad ada3fa15057205b7d3f727bba5cd26b5912e350f
# good: [decee2e8a9538ae5476e6cb3f4b7714c92a04a2b] V4L/DVB (12485): 
zl10353: correct implementation of FE_READ_UNCORRECTED_BLOCKS
git bisect good decee2e8a9538ae5476e6cb3f4b7714c92a04a2b
# good: [0ee7e4d6d4f58c3b2d9f0ca8ad8f63abda8694b1] V4L/DVB (12694): 
gspca - vc032x: Change the start exchanges of the sensor hv7131r.
git bisect good 0ee7e4d6d4f58c3b2d9f0ca8ad8f63abda8694b1
# good: [f58dc01ba2ca9fe3ab2ba4ca43d9c8a735cf62d8] percpu: generalize 
first chunk allocator selection
git bisect good f58dc01ba2ca9fe3ab2ba4ca43d9c8a735cf62d8
# good: [2f82af08fcc7dc01a7e98a49a5995a77e32a2925] Nicolas Pitre has a 
new email address
git bisect good 2f82af08fcc7dc01a7e98a49a5995a77e32a2925
# good: [cf88c79006bd6a09ad725ba0b34c0e23db20b19e] vmalloc: separate out 
insert_vmalloc_vm()
git bisect good cf88c79006bd6a09ad725ba0b34c0e23db20b19e
# good: [4518e6a0c038b98be4c480e6f4481e8676bd15dd] x86,percpu: use 
embedding for 64bit NUMA and page for 32bit NUMA
git bisect good 4518e6a0c038b98be4c480e6f4481e8676bd15dd
# good: [bcb2107fdbecef3de55d597d23453747af81ba88] sparc64: use 
embedding percpu first chunk allocator
git bisect good bcb2107fdbecef3de55d597d23453747af81ba88
# good: [5579fd7e6aed8860ea0c8e3f11897493153b10ad] Merge branch 
'for-next' into for-linus
git bisect good 5579fd7e6aed8860ea0c8e3f11897493153b10ad


Oh, wait, that commit was tested, in the middle of the log above.

-Andrew