gicv3: Change how we initialize its children.

[imp]

Summary

The current code is written such that all the attach routines can do so
in parallel. However, newbus serializes children today, and is likely to
do so in the future. Only allocate memory for unit 0. Add an assertion
that this memory is allocated for larger units.

Sponsored by: Netflix

[imp]

So this is the first in a series that adds support for kexec'ing on a gicv3 system after Linux has setup and used it...

[andrew]

sys/arm64/arm64/gicv3_its.c

689–691

This requires its0 to not fail before it calls gicv3_its_conftable_init. It might be safer to switch to if (conf_table != NULL) { ... to try to get something booting, even if one its is missing.

[imp]

sys/arm64/arm64/gicv3_its.c

689–691

Sure, I'll make this an if statement, but I have no way to test so I won't know if I caught all the base cases or not... Do you have any suggestions here?

[imp]

sys/arm64/arm64/gicv3_its.c

689–691

Do I need to also add seat-belts in gicv3_its_disable_intr and gicv3_its_enable_intr ?

[imp]

update per review

[andrew]

sys/arm64/arm64/gicv3_its.c

689–691

Sorry, I over selected. It should be for if (unit != 0) -> if (conf_table != NULL), not the KASSERT

[imp]

Create the conf table the first time through, rather than unit 0.

[imp]

sys/arm64/arm64/gicv3_its.c

689–691

Ah, that actually makes a lot more sense... And I'm a little less confused too and like the results.