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

Alan Cox alc at
Mon Dec 5 22:23:12 UTC 2011

On 12/5/2011 4:02 PM, Andriy Gapon wrote:
> on 05/12/2011 19:58 Alan Cox said the following:
>> On 12/05/2011 07:56, Andriy Gapon wrote:
>>> Pages should be marked busy only for some special occasions, wired pages are not
>>> normally busy; the correct explanation is quite a bit longer than this, the
>>> comment in the code explains VPO_BUSY as "page is in transit".  Right now this
>>> flag doesn't seem tom affect vboxdrv code but it may lead to surprises when some
>>> parts of code that are incorrect now are re-implemented properly:
>> VM_ALLOC_NOOBJ implies that the returned page does not have VPO_BUSY set.  From
>> the comment at the head of both vm_page_alloc() and vm_page_alloc_contig():
>>   *      VM_ALLOC_NOOBJ          page is not associated with an object and
>>   *                              should not have the flag VPO_BUSY set
> Ah, oops, forgot about this.
>> With regard to the message that the above link points to, I suspect that the
>> introduction of vm_page_alloc_contig() can be used to address the first problem
>> that you point out.  Specifically, one or more OBJT_PHYS vm objects could be
>> created and passed to vm_map_find() and then vm_page_alloc_contig() could be
>> used to fill these vm objects with memory.
> That's exactly what I was trying to do when I encountered a need for
> VM_ALLOC_NOOBJ - my object was not NULL.
> Alan, BTW, is it safe to map an OBJT_PHYS object into the kernel_map and into a
> user map (or a few of them) at the same time?

Yes, it is.


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