- Split the intr_table_lock into an sx lock used for most things, and a
spin lock to protect intrcnt_index. Originally I had this as a spin lock
so interrupt code could use it to lookup sources. However, we don't
actually do that because it would add a lot of overhead to interrupts,
and if we ever do support removing interrupt sources, we can use other
means to safely do so w/o locking in the interrupt handling code.
- Replace is_enabled (boolean) with is_handlers (a count of handlers) to
determine if a source is enabled or not. This allows us to notice when
a source is no longer in use. When that happens, we now invoke a new
PIC method (pic_disable_intr()) to inform the PIC driver that the
source is no longer in use. The I/O APIC driver frees the APIC IDT
vector when this happens. The MSI driver no longer needs to have a
hack to clear is_enabled during msi_alloc() and msix_alloc() as a result
of this change as well.
- Add an apic_disable_vector() to reset an IDT vector back to Xrsvd to
complement apic_enable_vector() and use it in the I/O APIC and MSI code
when freeing an IDT vector.
- Add a new nexus hook: nexus_add_irq() to ask the nexus driver to add an
IRQ to its irq_rman. The MSI code uses this when it creates new
interrupt sources to let the nexus know about newly valid IRQs.
Previously the msi_alloc() and msix_alloc() passed some extra stuff
back to the nexus methods which then added the IRQs. This approach is
a bit cleaner.
- Change the MSI sx lock to a mutex. If we need to create new sources,
drop the lock, create the required number of sources, then get the lock
and try the allocation again.
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