Re: [RFC] [VTD][patch 1/3] vt-d support for pci passthrough: kvm-vtd--kernel.patch

[Avi Kivity <avi@qumranet.com>]

Anthony Liguori wrote:

    

>> What should be done for unmodified guest where there is no PV driver in
>> the guest?  Would a call to mlock() from
>> qemu/hw/pci-passthrough.c/add_pci_passthrough_device() a reasonable
>> thing to do?
>>   
>>     
>
> Yup.  The idea is to ensure that the memory is always present, without 
> necessarily taking a reference to it.  This allows for memory reclaiming 
> which should allow for things like NUMA page migration.  We can't swap 
> of course but that doesn't mean reclaimation isn't useful.
>   

I don't think we can do page migration with VT-d.  You need to be able 
to detect whether the page has been changed by dma after you've copied 
it but before you changed the pte, but VT-d doesn't allow that AFAICT.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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