Message-ID: <4BB76DA1.4050904@redhat.com>
Date: Sat, 03 Apr 2010 19:32:33 +0300
From: Avi Kivity <avi@redhat.com>
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To: Sridhar Samudrala <sri@us.ibm.com>
CC: xiaohui.xin@intel.com, netdev@vger.kernel.org, kvm@vger.kernel.org,
       linux-kernel@vger.kernel.org, mingo@elte.hu, mst@redhat.com,
       jdike@c2.user-mode-linux.org, davem@davemloft.net
Subject: Re: [RFC][PATCH v2 0/3] Provide a zero-copy method on KVM virtio-net.
References: <1270193100-6769-1-git-send-email-xiaohui.xin@intel.com> <1270252268.13897.14.camel@w-sridhar.beaverton.ibm.com>
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On 04/03/2010 02:51 AM, Sridhar Samudrala wrote:
> On Fri, 2010-04-02 at 15:25 +0800, xiaohui.xin@intel.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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