RE: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts

David Laight
2013-05-09T13:28:13Z

> Some MPIC implementations tend to generate a spurrious IRQ in the case
> of level IRQs going away. IE. they still remember an event occurred and
> interrupt the processor, but on IACK return the spurious vector. However
> that isn't guaranteed to be the case and it is perfectly ok (and a good
> idea) for the PIC to just stop asserting the external interrupt line if
> the original device interrupt goes away (and it's configured as level
> sensitive).

That will happen if the IRQ goes away while the cpu is performing
the IACK sequence.
If the IRQ goes away while the cpu has interrupts masked then
the cpu won't start the interrupt sequence and then try to
read a vector when no interrupt is pending.

David