Jan Kiszka wrote: > On 2011-01-17 17:33, Alexander Graf wrote: > >> Jan Kiszka wrote: >> >>> On 2011-01-17 17:04, Alexander Graf wrote: >>> >>> >>>> Jan Kiszka wrote: >>>> >>>> >>>>> On 2011-01-17 17:00, Alexander Graf wrote: >>>>> >>>>> >>>>> >>>>>> Jan Kiszka wrote: >>>>>> >>>>>> >>>>>> >>>>>>> On 2010-12-20 22:13, Alexander Graf wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>>> When not using MSI, receiving an interrupt while the interrupt line is >>>>>>>> active >>>>>>>> pulses the interrupt line. Without this, guests don't realize that a >>>>>>>> new >>>>>>>> interrupt occured. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> This doesn't look OK. The device model should look at the currently used >>>>>>> mode and switch between edge and level triggering accordingly. As it >>>>>>> appears like this is what it already does, this change may just paper >>>>>>> over the real issue. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> Well, I have this internal abstraction to make edge and level triggered >>>>>> interrupt triggering easier. irq_lower is a simple nop for the edge case. >>>>>> >>>>>> >>>>>> >>>>>> >>>>> I'm concerned about the artificial edge you generate for the level >>>>> triggered case. That's not like real hw behaves. If you need it, >>>>> something else might still be broken. >>>>> >>>>> >>>>> >>>> Hrm. So worst case we generate a spurious interrupt? >>>> >>>> >>>> >>> Worse might also be that unknown issue that force you to inject an IRQ >>> here. We don't know. That's probably worst. >>> >>> >> Well, IIRC the issue was that usually a level high interrupt line would >> simply retrigger an interrupt after enabling the interrupt line in the >> APIC again. Unless my memory completely fails on me, that didn't happen, >> so I added the manual retrigger on a partial command ACK in ahci code. >> >> > > How many other device models require this workaround? And is this a > limitation of a specific irqchip model or of the irq layer (I can't > believe it's the latter though)? All fairly suspicious... >
I don't know :). Alex
