riscv: plic: plic_init_controller won't clear any pending interrupt #1482
Description
This is because on boot hart (BSP) we masked all the interrupt for the current hart before we claim pending interrupts, I.e.,
init_cpu -> initLocalIRQController -> plic_init_hart
Later when we do
init_plat -> initIRQController -> plic_init_controller
Code ref:
seL4/include/drivers/irq/riscv_plic0.h
Lines 162 to 192 in ab5192f
seL4/src/arch/riscv/kernel/boot.c
Lines 227 to 235 in ab5192f
Per the spec, you can't ack/EOI an interrupt from a hart that doesn't have that interrupt enabled. Linux has stumbled upon the same issue:
https://lore.kernel.org/all/[email protected]/
We don't have to clear any pending interrupts in this function, because even if we clear it by enabling the interrupt, claiming it, then disabling it, it can still be raised again. The proper approach should be just don't care, as the interrupt is already disabled for the hart.