On Wed, Jan 06, 2010 at 01:51:54PM -0600, Anthony Liguori wrote: > On 01/06/2010 01:44 PM, Gleb Natapov wrote: > >On Wed, Jan 06, 2010 at 01:23:28PM -0600, Anthony Liguori wrote: > >>On 01/06/2010 01:20 PM, Beth Kon wrote: > >>>Beth Kon wrote: > >>>>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? > >>>Anthony just explained that on x86, even edge-triggered interrupts > >>>are queued in the apic and an eoi will occur, so this is not > >>>different than the PIT. > >>Not quite queued in the sense that multiple events will be delivered > >>in order, but I think the point is that you can still detect whether > >>delivery succeeded by counting APIC EOIs. > >> > >>The trouble is that historically we've struggled with doing this in > >>userspace. Maybe it's time to revisit. > >> > >We reinject PIT interrupts from kernel and RTC interrupts from > >userspace. > > Because we can determine that we've missed an RTC interrupt in > userspace. We cannot determine this with the PIT without adding a > hook into the userspace apic that lets us know whether an injection > failed or not. > We have exactly that hook in apic already and that's how RTC determines that interrupt was coalesced. -- 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
