On Thu, Dec 07, 2017 at 04:31:27PM +0800, Jason Wang wrote: > > > 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.co...@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.
Okay, that is a different use case: 1. VM<->physical NIC: macvtap 2. VM<->host userspace: vhost-user 3. VM<->host/container: vethtap or pair mode 4. VM<->VM: vhost-pci Stefan
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