Generalise the arm64 ASID allocator

[andrew]

Summary

The requirements of an Address Space ID allocator and a Virtual Machine ID
allocator are similar. Generalise the former code so it can be used with
the latter.

[andrew]

Remove an unused variable

[alc]

Is your overall strategy to incrementally replace PMAP_ASSERT_STAGE1(pmap)'s by correct handling of stage 2 PTE?

sys/arm64/arm64/pmap.c

998

I would suggest moving the second sentence inside pmap_init_asids() and change the wording to: "We may be too early in ..."

5883

if (pmap->pm_stage == PM_STAGE1) ... else ...?

[andrew]

In D23831#523873, @alc wrote:

Is your overall strategy to incrementally replace PMAP_ASSERT_STAGE1(pmap)'s by correct handling of stage 2 PTE?

Yes. I'm currently working on pmap_enter and just need to implement cache and tlb handling for it.

sys/arm64/arm64/pmap.c

5883

I'll add PMAP_ASSERT_STAGE1(pmap); for now as the process for VMID reset looks like it will be more complex, e.g. may need to call into the hypervisor.

[andrew]

• Move a comment to follow code into pmap_init_asids
• Assert we have a Stage 1 pmap in pmap_reset_asid_set and remove extra whitespace