Zachary Amsden wrote: > On Wed, 2007-11-21 at 09:13 +0200, Avi Kivity wrote: > > >> Where the device is implemented is an implementation detail that should >> be hidden from the guest, isn't that one of the strengths of >> virtualization? Two examples: a file-based block device implemented in >> qemu gives you fancy file formats with encryption and compression, while >> the same device implemented in the kernel gives you a low-overhead path >> directly to a zillion-disk SAN volume. Or a user-level network device >> capable of running with the slirp stack and no permissions vs. the >> kernel device running copyless most of the time and using a dma engine >> for the rest but requiring you to be good friends with the admin. >> >> The user should expect zero reconfigurations moving a VM from one model >> to the other. >> > > I think that is pretty insightful, and indeed, is probably the only > reason we would ever consider using a virtio based driver. > > But is this really a virtualization problem, and is virtio the right > place to solve it? Doesn't I/O hotplug with multipathing or NIC teaming > provide the same infrastructure in a way that is useful in more than > just a virtualization context? >
With the aid of a dictionary I was able to understand about half the words in the last sentence. Moving from device to device using hotplug+multipath is complex to configure, available on only some guests, uses rarely-exercised paths in the guest OS, and only works for a few types of devices (network and block). Having host independence in the device means you can change the device implementation for, say, a display driver (consider, for example, a vmgl+virtio driver, which can be implemented in userspace or tunneled via virtio-over-tcp to some remote display without going through userspace, without the guest knowing about it). -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
