On 24/04/20 18:25, Jim Mattson wrote: >> Assuming we're going forward with this, at an absolute minimum the RDMSRs >> need to be wrapped with checks on host _and_ guest support for the emulated >> behavior. Given the significant overhead, this might even be something >> that should require an extra opt-in from userspace to enable. > > I would like to see performance data before enabling this unconditionally. I wouldn't want this to be enabled unconditionally anyway, because you need to take into account live migration to and from processors that do not have APERF/MPERF support. Paolo
