Subject: Re: [RFC][PATCH v2 0/3] Provide a zero-copy method on KVM virtio-net.

From: Avi Kivity <[email-masked]>
Date: Sat, 03 Apr 2010 19:32:33 +0300

On 04/03/2010 02:51 AM, Sridhar Samudrala wrote:
> On Fri, 2010-04-02 at 15:25 +0800, [email-masked] wrote:
>    
>> The idea is simple, just to pin the guest VM user space and then
>> let host NIC driver has the chance to directly DMA to it.
>> The patches are based on vhost-net backend driver. We add a device
>> which provides proto_ops as sendmsg/recvmsg to vhost-net to
>> send/recv directly to/from the NIC driver. KVM guest who use the
>> vhost-net backend may bind any ethX interface in the host side to
>> get copyless data transfer thru guest virtio-net frontend.
>>      
> What is the advantage of this approach compared to PCI-passthrough
> of the host NIC to the guest?
>    

swapping/ksm/etc
independence from host hardware
live migration

> Does this require pinning of the entire guest memory? Or only the
> send/receive buffers?
>    

If done correctly, just the send/receive buffers.

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