Re: [Xen-devel] xenstored crashes with SIGSEGV

[Philipp Hahn <hahn@xxxxxxxxxxxxx>]

Hello,
On 12.03.2015 19:17, Oleg Nesterov wrote:
> On 03/12, Philipp Hahn wrote:
>>
>> Have you seen any other corruption
> 
> No,
> 
>> or is one of your patches likely to
>> fix something like the issue mentioned above:
> 
> I am not sure I even understand the problem above ;) I mean, after the quick
> look I do not see how this connects to FPU. $rdi == 2 looks obviously wrong.

In December we found some strange crashes of a Xen daemon, but other
processes crashed as well. One strange pattern Ian found was some
0x..00.ff pattern, which seems to have come from some SSE register
corruption.
That is why we upgrades to 3.10.62, which contains some fixes for saving
the FPU state. If my memory is correct the FPU registers share the space
with the MMU/SSE registers, so that seemed a good candidate.

You might want to take a look at
<http://lists.xenproject.org/archives/html/xen-devel/2014-12/msg01583.html>,
where you find the mail thread from December.

>>> $ git l1 --grep fpu v3.10.. -- arch/x86
>>> c7b228a Merge branch 'x86-fpu-for-linus' of 
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>> dc56c0f x86, fpu: Shift "fpu_counter = 0" from copy_thread() to 
>>> arch_dup_task_struct()
>>> 5e23fee x86, fpu: copy_process: Sanitize fpu->last_cpu initialization
>>> f185350 x86, fpu: copy_process: Avoid fpu_alloc/copy if !used_math()
>>> 31d9633 x86, fpu: Change __thread_fpu_begin() to use use_eager_fpu()
> 
> This is only cleanups... I do not think this series can fix something.

My guess from reading your description, but still tanks for your help.

Philipp

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