On Tue, Dec 14, 2010 at 03:49:37PM +0200, Avi Kivity wrote: > On 12/14/2010 03:40 PM, Glauber Costa wrote: > >> > >> What is the motivation for this? Are there any important guests that > >> use the pmtimer? > >Avi, > > > >All older RHEL and Windows, for example, would benefit for this. > > They only benefit from it because we don't provide HPET. If we did, > the guests would use HPET in preference to pmtimer, since HPET is so > much better than pmtimer (yet still sucks in an absolute sense). > > >> If anything I'd expect hpet or the Microsoft synthetic timers to be a > >> lot more important. > > > >True. But also a lot more work. > >Implementing just the pm timer counter - not the whole of it - in > >kernel, gives us a lot of gain with not very much effort. Patch is > >pretty simple, as you can see, and most of it is even code to turn it > >on/off, etc. > > > > Partial emulation is not something I like since it causes a fuzzy > kernel/user boundary. In this case, transitioning to userspace when > interrupts are enabled doesn't look so hot. Are you sure all guests > that benefit from this don't enable the pmtimer interrupt? What > about the transition? Will we have a time discontinuity when that > happens? > > What I'd really like to see is this stuff implemented in bytecode, > unfortunately that's a lot of work which will be very hard to > upstream. > <joke> Just use ACPI bytecode. It is upstream already. </joke> -- Gleb. -- 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
