* Avi Kivity <avi@xxxxxxxxxx> wrote: > Or do you mean to define a new, kvm-specific pmu model and feed it off the > host pmu? In this case all the guests will need to be taught about it, > which raises the compatibility problem. You are missing two big things wrt. compatibility here: 1) The first upgrade overhead a one time overhead only. 2) Once a Linux guest has upgraded, it will work in the future, with _any_ future CPU - _without_ having to upgrade the guest! Dont you see the advantage of that? You can instrument an old system on new hardware, without having to upgrade that guest for the new CPU support. With the 'steal the PMU' messy approach the guest OS has to be upgraded to the new CPU type all the time. Ad infinitum. Ingo -- 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