On 08/05/2012 04:48 PM, Gleb Natapov wrote: >> >> >> During guest boot up, some of these jump keys will change, no? Does >> >> this mean a stop_machine() or equivalent? I'm worried about real-time >> >> response or one guest being affected by another. >> >> >> > Yes, SW enable bit changes during boot. The jump label triggerable by a >> > guest are rate limited though. So stop machine will not happen more then >> > once per second even with malicious guests. >> >> I'm not talking about a malicious guest, just a guest that is booting up >> normally but kills real-time response for another guest (or just induces >> a large hiccup in a non-real-time guest, but we don't guarantee anything >> for those). >> >> We don't support real-time guests now, but Jan has plans. >> > For such setup jump labels have to be compiled out from the kernel > completely. Anything that calls stop_machine does not play well with > real time. > > Guest can cause stop machine on boot today already by detecting PMU and > configuring NMI watchdog. The host can prevent this by leaving disabling the guest pmu. But disabling jump labels for real-time kernels may be acceptable too. We can probably to it at run time by forcing the slow path at all times. -- 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
