Re: [Qemu-devel] [virtio-dev] [PATCH v3 0/7] Vhost-pci for inter-VM communication

[Jason Wang <jasowang@redhat.com>]

On 2017年12月07日 16:04, Stefan Hajnoczi wrote:
> On Thu, Dec 7, 2017 at 7:54 AM, Avi Cohen (A) <avi.cohen@huawei.com> wrote:
> > There is already a  virtio mechanism in which 2 VMs assigned a virtio device , are communicating via a veth pair  in the host .
> > KVM just passes  a pointer of the page of the writer VM to the reader VM - resulting  in  excellent performance (no vSwitch in the middle)
> > **Question**:  What is the advantage of vhost-pci compared to this ?
> Which mechanism do you mean?
>
> vhost-pci will allow VM-to-VM communication without vmexits when
> polling mode is used.  Does the mechanism you are thinking about
> require vmexits?
>
> Stefan

I guess what Avi means is probably veth tap support (RFC) here:

https://www.spinics.net/lists/netdev/msg454040.html

But in fact, we don't need veth at all, by using rx handler trick, we 
can easily implement pair mode on TUN/TAP.

Thanks