On Mon, 15 Dec 2008 17:01:14 -0600 Anthony Liguori <anthony@xxxxxxxxxxxxx> wrote: > David Miller wrote: > > From: Anthony Liguori <anthony@xxxxxxxxxxxxx> > > Date: Mon, 15 Dec 2008 14:44:26 -0600 > > > > > >> We want this communication mechanism to be simple and reliable as we > >> want to implement the backends drivers in the host userspace with > >> minimum mess. > >> > > > > One implication of your statement here is that TCP is unreliable. > > That's absolutely not true. > > > > No, TCP falls under the not simple category because it requires the > backend to have access to a TCP/IP stack. > > >> Within the guest, we need the interface to be always available and > >> we need an addressing scheme that is hypervisor specific. Yes, we > >> can build this all on top of TCP/IP. We could even build it on top > >> of a serial port. Both have their down-sides wrt reliability and > >> complexity. > >> > > > > I don't know of any zero-copy through the hypervisor mechanisms for > > serial ports, but I know we do that with the various virtualization > > network devices. > > > > Yes, and I went down the road of using a dedicated network device and > using raw ethernet as the protocol. The thing that killed that was the > fact that it's not reliable. You need something like TCP to add > reliability. > > But that's a lot of work and a bit backwards. Use a unreliable > transport but use TCP on top of it to get reliability. Our link > (virtio) is inherently reliable so why not just expose a reliable > interface to userspace? > > >> Do you have another recommendation? > >> > > > > I don't have to make alternative recommendations until you can > > show that what we have can't solve the problem acceptably, and > > TCP emphatically can. > > > > It can solve the problem but I don't think it's the best way to solve > the problem mainly because the complexity it demands on the backend. "Those who don't understand TCP are doomed to reimplement it, badly." _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
