On 07/26/2012 07:40 PM, Alex Williamson wrote: > On Thu, 2012-07-26 at 19:06 +0300, Avi Kivity wrote: >> On 07/26/2012 05:56 PM, Alex Williamson wrote: >> > >> > Both KVM and VFIO do strive to make the device in the guest look as much >> > like it does on bare metal as possible, but we don't guarantee they're >> > identical and we don't guarantee to match each other. >> >> btw, this is somewhat problematic, conceivably this could break a guest >> (due to a guest bug). But with device assignment the compatibility >> requirements can be relaxed a bit since there is no live migration. > > Well, I would hope that things work better in vfio and we work to make > that the recommended method of device assignment. We can't hold one > back to make things identical. The only barrier I see to this is that > vfio focuses on security, enforcing things like ACS to make sure devices > can't do DMA to other devices outside of the group whereas KVM > assignment will let you attempt to do nearly anything and counts on > libvirt to only let the user attempt to do sane things. As you say, > there's no live migration with device assignment, so absolute identical > config space is not a requirement and the difference we do have should > be sufficiently subtle that the guest doesn't care boot-to-boot. We could add a strict backward compatibility option that forces the layout, but it isn't worth it. -- error compiling committee.c: too many arguments to function -- 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
