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

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Message-ID: <4BB76DA1.4050904@redhat.com>
Date:	Sat, 03 Apr 2010 19:32:33 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Sridhar Samudrala <sri@...ibm.com>
CC:	xiaohui.xin@...el.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu, mst@...hat.com,
	jdike@...user-mode-linux.org, davem@...emloft.net
Subject: Re: [RFC][PATCH v2 0/3] Provide a zero-copy method on KVM virtio-net.

On 04/03/2010 02:51 AM, Sridhar Samudrala wrote:
> On Fri, 2010-04-02 at 15:25 +0800, xiaohui.xin@...el.com 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.

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