Freeze with 10.0 and VirtualBox {4.1.4|4.1.6|4.1.51r38464}

[Gustau Pérez]

>>>
>>> Using new vm_page_alloc_contig() may be a better option here. Can't help
>>> with patch, stuck with pre Nov 15 CURRENT myself.
>>

    Ok. The third parameter of vm_page_alloc_contig says the caller has 
to specify an allocation class. Which one should we use?

    Also the vm_object_t and the vm_memattr_t are are beyond my 
knowledge. I'm checking Arch Book but I have no clue. Here I'm lost.

> Not "also", but instead.  And only for managed pages.  For unmanaged pages a
> caller doesn't have to acquire anything.
> The relevant change in head has happened much much earlier than r227568.
>
> And this is a totally different issue from the vm_phys_alloc_contig issue.
> Let's not mix them.
>

   I changed the code hold the lock of vm_page_queue_free_mtx. The 
machine them panic because of a page not present.

       http://pastebin.com/hGHCJqEP

   I don't understand why the bt doesn't contain the complete trace of 
the vbox kmod. That would give us a complete clue of what is going on.

   OTOH this bt makes me think that Gleb's suggestion is correct and 
vm_page_alloc_contig would appear to be a better option. However I'm not 
sure, what do you think?