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

From: Avi Kivity
Date: Sat Apr 03 2010 - 12:33:04 EST

On 04/03/2010 02:51 AM, Sridhar Samudrala wrote:
On Fri, 2010-04-02 at 15:25 +0800, 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?

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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