Re: [PATCH 3/3] virtio PCI device

[Dor Laor <dor.laor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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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