Re: Why my interrupt is not connected? qemu_irq_is_connected( ) returns false.

[Peter Maydell]

On Mon, 4 Apr 2022 at 14:29, Chan Kim <ckim@etri.re.kr> wrote:
>
> Hello all,
>
> I have assigned my device's irq at SPI 176 (= INTID 208 ).
> And I found in the qemu's gicv3_cpuif_update function below, the 
> icc_hppi_can_preempt(cs) returns false because cs->hppi.prio == 0xff.
> I understand this means the interrupt I made is of priority 0xff (the 
> lowest?).

No, prio = 0xff means "no pending interrupt available" (either there
really is none in the pending state, or interrupts are disabled
generally, or a specific interrupt which might otherwise be signalled
to the CPU has been disabled).

> How can I make my interrupt have higher priority other that 0xff?

Priorities are set by the guest OS, which programs the GIC
priority registers with the priorities it wants to use for
the interrupt. (0xff is not actually a valid priority for
an interrupt, which is why we can use it as our "nothing
is pending" value.)

-- PMM