Arnd Bergmann wrote: >> 3) given an fd, treat a vhost-style interface >> > > This could mean two things, not sure which one you mean. Either the > file descriptor could be the vhost file descriptor, or the socket or tap file > descriptor from above, with qemu operating on the vhost interface itself. > > Either option has its advantages, but I guess we should only implement > one of the two to keep it simple. >
I was thinking the socket/tap descriptor. >> I believe we should continue supporting the mechanisms we support >> today. However, for people that invoke qemu directly from the command >> line, I believe we should provide a mechanism like the tap helper that >> can be used to call out to a separate program to create these initial >> file descriptors. We'll have to think about how we can make this >> integrate well so that the syntax isn't clumsy. >> > > Right. I wonder if this helper should integrate with netcf as an abstraction, > or if we should rather do something generic. It may also be a good idea > to let the helper decide which of the three options you listed to use > and pass that back to qemu unless the user overrides it. The decision > probably needs to be host specific, depending e.g. on the availability > and version of tools (brctl, iproute, maybe tunctl, ...), the respective > kernel modules (vhost, macvlan, bridge, tun, ...) and policy (VEPA, vlan, > ebtables). Ideally the approach should be generic enough to work on > other platforms (BSD, Solaris, Windows, ...). > For helpers, I think I'd like to stick with what we currently support, and then allow for a robust way for there to be independent projects that implement their own helpers. For instance, I would love it if netcf had a qemu network "plugin" helper. There's just too much in the networking space all wrapped up in layers of policy decisions. I think it's time to move it out of qemu. > One thing I realized the last time we discussed the helper approach is > that qemu should not need to know or care about the arguments passed > to the helper, otherwise you get all the complexity back in qemu that > you're trying to avoid. Maybe for 0.13 we can convert -net socket and > -net tap to just pass all their options to the helper and move that code > out of qemu, along with introducting the new syntax. > Yes, I was thinking the same thing. New syntax may need exploring. > Another unrelated issue that I think needs to be addressed in a > network code cleanup is adding better support for multi-queue > transmit and receive. I've prepared macvtap for that by letting you > open the chardev multiple times to get one queue per guest CPU, > but that needs to be supported by qemu and virtio-net as well > to actually parallelize network operation. Ideally, two guest CPUs > should be able to transmit and receive on separate queues of the > adapter without ever having to access any shared resources. > Multiqueue adds another dimension but I think your approach is pretty much right on the money. Have multiple fds for each queue and we would support a mechanism with helpers to receive multiple fds as appropriate. Regards, Anthony Liguori _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
