Re: [Xen-devel] qeustion: a panic in __do_update_va_mapping()

["Xuquan (Quan Xu)" <xuquan8@xxxxxxxxxx>]

On November 01, 2016 8:00 PM, Andrew Cooper wrote:
>On 01/11/16 11:57, Xuquan (Quan Xu) wrote:
>> On November 01, 2016 7:41 PM, Andrew Cooper
><andrew.cooper3@xxxxxxxxxx > wrote:
>>> On 01/11/16 11:23, Xuquan (Quan Xu) wrote:
>>>> On November 01, 2016 7:16 PM, Andrew Cooper <
>>> andrew.cooper3@xxxxxxxxxx > wrote:
>>>>> On 01/11/16 11:01, Xuquan (Quan Xu) wrote:
>>>>>> Hi Andrew,
>>>>>>
>>>>>> When I run some application with Xen, I encounter a Panic with log
>>>>>> as the
>>>>> bottom of this email.
>>>>>> I find this panic is as similar as your fix e4e9d2d4e76bd8fe22
>'x86/p2m-ept:
>>>>> don't unmap the EPT pagetable while it is still in use'.
>>>>>
>>>>> Its not the same.  My fix was for a pagefault.  Your crash is
>>>>> hitting a
>>>>> BUG()
>>>>>
>>>>> You need to investigate which BUG() is being hit (you are clearly
>>>>> not using staging, as page_alloc.c:429 is outside of a function), and why.
>>>>>
>>>> It is not using staging, a internal version, but the
>>>> __do_update_va_mapping() is
>>> the same..
>>>> So I think it is similar to staging.
>>> __do_update_va_mapping() is not relevant.  Your problem is in
>>> alloc_heap_pages(), not __do_update_va_mapping().
>>>
>>
>> Andrew, thanks for your help..
>>
>> Check it,
>> the BUG() is from
>> do_memory_op() -- alloc_domheap_pages() -- alloc_heap_pages()..
>> , not from  __do_update_va_mapping().
>>
>> If so, I think the information is too limited to debug..
>>
>> the BUG() is being hit at:
>> ...
>> alloc_heap_pages()
>>     for ( i = 0; i < (1 << order); i++ )
>>     {
>>         /* Reference count must continuously be zero for free pages. */
>>         BUG_ON(pg[i].count_info != PGC_state_free); ...
>>
>>
>> I guess I hit a 'count_info == -1', more put_page() is called to return the 
>> page..
>
>Yes.  This means that you have a reference counting error elsewhere in
>the hypervisor, and something is dropping too many references.
>

:(:(..
Any method to address it? 

Quan

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