On Wed, Apr 14, 2010 at 10:39:49PM +0200, Arnd Bergmann wrote: > On Wednesday 14 April 2010 22:31:42 Michael S. Tsirkin wrote: > > On Wed, Apr 14, 2010 at 06:35:57PM +0200, Arnd Bergmann wrote: > > > On Wednesday 14 April 2010, Michael S. Tsirkin wrote: > > > > > > > > > > > > qemu needs the ability to inject raw packets into device > > > > > > from userspace, bypassing vhost/virtio (for live migration). > > > > > > > > > > Ok, but since there is only a write callback and no read, it won't > > > > > actually be able to do this with the current code, right? > > > > > > > > I think it'll work as is, with vhost qemu only ever writes, > > > > never reads from device. We'll also never need GSO etc > > > > which is a large part of what tap does (and macvtap will > > > > have to do). > > > > > > Ah, I see. I didn't realize that qemu needs to write to the > > > device even if vhost is used. But for the case of migration to > > > another machine without vhost, wouldn't qemu also need to read? > > > > Not that I know. Why? > > Well, if the guest not only wants to send data but also receive > frames coming from other machines, they need to get from the kernel > into qemu, and the only way I can see for doing that is to read > from this device if there is no vhost support around on the new > machine. > > Maybe we're talking about different things here. > > Arnd mpassthrough is currently useless without vhost. If the new machine has no vhost, it can't use mpassthrough :) -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
