On Thursday 07 January 2010 02:36:26 Beth Kon wrote: > Dor Laor wrote: > > On 01/06/2010 12:09 PM, Gleb Natapov wrote: > >> On Wed, Jan 06, 2010 at 05:48:52PM +0800, Sheng Yang wrote: > >>> Hi Beth > >>> > >>> I still found the emulated HPET would result in some boot failure. For > >>> example, on my 2.6.30, with HPET enabled, the kernel would fail > >>> check_timer(), > >>> especially in timer_irq_works(). > >>> > >>> The testing of timer_irq_works() is let 10 ticks pass(using > >>> mdelay()), and > >>> want to confirm the clock source with at least 5 ticks advanced in > >>> jiffies. > >>> I've checked that, on my machine, it would mostly get only 4 ticks > >>> when HPET > >>> enabled, then fail the test. On the other hand, if I using PIT, it > >>> would get > >>> more than 10 ticks(maybe understandable if some complementary ticks > >>> there). Of > >>> course, extend the ticks count/mdelay() time can work. > >>> > >>> I think it's a major issue of HPET. And it maybe just due to a too long > >>> userspace path for interrupt injection... If it's true, I think it's > >>> not easy > >>> to deal with it. > >> > >> PIT tick are reinjected automatically, HPET should probably do the same > >> although it may just create another set of problems. > > > > Older Linux do automatic adjustment for lost ticks so automatic > > reinjection causes time to run too fast. This is why we added the > > -no-kvm-pit-reinject flag... > > > > It took lots of time to pit/rtc to stabilize, in order of seriously > > consider the hpet emulation, lots of testing should be done. > > I will try to look into this. Since HPET is edge-triggered, looks like > this problem is of a different nature than PIT. Is this a solid failure > or intermittent? > At least for v2.6.30 in my box, it always fails... Of course, I believe the chance of successful injecting enough interrupt depends on the many factors. So I think out target can be: not far behind what PIT can do... -- regards Yang, Sheng -- 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
