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

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

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..

Quan

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