Rusty Russell wrote: > Hi all, > > Just finished my prototype of inter-guest virtio, using networking as an > example. Each guest mmaps the other's address space and uses a FIFO for > notifications. > > There are two issues with this approach. The first is that neither guest > can change its mappings. See patch 1. Avi mentioned that with MMU notifiers, it may be possible to introduce a new kernel mechanism whereas you could map an arbitrary region of one process's memory into another process. This would address this problem quite nicely. > The second is that our feature > configuration is "host presents, guest chooses" which breaks down when we > don't know the capabilities of each guest. In particular, TSO capability for > networking. > There are three possible solutions: > 1) Just offer the lowest common denominator to both sides (ie. no features). > This is what I do with lguest in these patches. > 2) Offer something and handle the case where one Guest accepts and another > doesn't by emulating it. ie. de-TSO the packets manually. > 3) "Hot unplug" the device from the guest which asks for the greater features, > then re-add it offering less features. Requires hotplug in the guest OS. > 4) Add a feature negotiation feature. The feature that gets set is the "feature negotiate" feature. If a guest doesn't support feature negotiation, you end up with the least-common denominator (no features). If both guests support feature negotiation, you can then add something new to determine the true common subset. > I haven't tuned or even benchmarked these patches, but it pings! > Very nice! It's particularly cool that it was possible entirely in userspace. Regards, Anthony Liguori > Rusty. > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > kvm-devel mailing list > kvm-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/kvm-devel > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
