Re: [kvm-devel] [PATCH 3/3] virtio PCI device

Dor Laor
2007-11-08T23:51:14Z

Anthony Liguori wrote:
> Avi Kivity wrote:
>
>> Anthony Liguori wrote:
>>
>>
>>> This is a PCI device that implements a transport for virtio. It allows virtio
>>> devices to be used by QEMU based VMMs like KVM or Xen.
>>>
>>>
>>>
>>>
>> Didn't see support for dma.
>>
>
> Not sure what you're expecting there. Using dma_ops in virtio_ring?
>
>
>> I think that with Amit's pvdma patches you
>> can support dma-capable devices as well without too much fuss.
>>
>>
>
> What is the use case you're thinking of? A semi-paravirt driver that
> does dma directly to a device?
>
> Regards,
>
> Anthony Liguori
>
>
You would also lose performance since pv-dma will trigger an exit for
each virtio io while
virtio kicks the hypervisor after several IOs were queued.
>
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