Change the x86 code to allocate IDT vectors on-demand when an interrupt

source is first enabled similar to how intr_event's now allocate ithreads
on-demand.  Previously, we would map IDT vectors 1:1 to IRQs.  Since we
only have 191 available IDT vectors for I/O interrupts, this limited us
to only supporting IRQs 0-190 corresponding to the first 190 I/O APIC
intpins.  On many machines, however, each PCI-X bus has its own APIC even
though it only has 1 or 2 devices, thus, we were reserving between 24 and
32 IRQs just for 1 or 2 devices and thus 24 or 32 IDT vectors.  With this
change, a machine with 100 IRQs but only 5 in use will only use up 5 IDT
vectors.  Also, this change provides an API (apic_alloc_vector() and
apic_free_vector()) that will allow a future MSI interrupt source driver to
request IDT vectors for use by MSI interrupts on x86 machines.

Tested on:	amd64, i386

0 files changed, 0 insertions, 0 deletions