On 01.09.2010, at 13:45, Avi Kivity wrote: > On 09/01/2010 12:38 PM, Alexander Graf wrote: >> On 01.09.2010, at 09:41, Avi Kivity wrote: >> >>> On 08/31/2010 01:07 PM, Alexander Graf wrote: >>>> KVM on PowerPC used to have completely broken interrupt logic. Usually, >>>> interrupts work by having a PIC that pulls a line up/down, so the CPU knows >>>> that an interrupt is active. This line stays active until some action is >>>> done to the PIC to release the line. >>>> >>>> On KVM for PPC, we just checked if there was an interrupt pending and >>>> pulled >>>> a line in the kernel module. We never released it though, hoping that >>>> kernel >>>> space would just declare an interrupt as released when injected - which is >>>> wrong. >>>> >>>> To fix this, we need to completely redesign the interrupt injection logic. >>>> Whenever an interrupt line gets triggered, we need to notify kernel space >>>> that the line is up. Whenever it gets released, we do the same. This way >>>> we can assure that the interrupt state is always known to kernel space. >>>> >>>> This fixes random stalls in KVM guests on PowerPC that were waiting for >>>> an interrupt while everyone else thought they received it already. >>> This is more or less equivalent to KVM_IRQ_LINE. >> My question was if you think the internal C interface is generic enough or >> if it needs a lot more magic for x86 anyways :). >> > > So you noticed I avoided it. Well, being forced to look, I don't think it's > worthwhile to try to be generic here. Both the PIC<->APIC and the > APIC<->core interfaces are too complicated to be modelled by a single line.
Makes sense. Well, I guess it doesn't hurt to have the interface as is and only implement it for PPC for now. Alex
