On Mon, 30 Nov 2020 09:30:33 +0100 Niklas Schnelle <schne...@linux.ibm.com> wrote:
> I'm not really familiar, with it but I think this is closely related > to what I asked Bernd Nerz. I fear that if CPUs go away we might already > be in trouble at the firmware/hardware/platform level because the CPU Address > is > "programmed into the device" so to speak. Thus a directed interrupt from > a device may race with anything reordering/removing CPUs even if > CPU addresses of dead CPUs are not reused and the mapping is stable. From your answer, I read that CPU hot-unplug is supported for LPAR. > > Furthermore our floating fallback path will try to send a SIGP > to the target CPU which clearly doesn't work when that is permanently > gone. Either way I think these issues are out of scope for this fix > so I will go ahead and merge this. I agree, it makes on sense to delay this fix. But if CPU hot-unplug is supported, I believe we should react when a CPU is unplugged, that is a target of directed interrupts. My guess is, that in this scenario transient hiccups are unavoidable, and thus should be accepted, but we should make sure that we recover. Regards, Halil
