cvs commit: src/sys/amd64/amd64 io_apic.c local_apic.c src/sys/amd64/include apicvar.h intr_machdep.h src/sys/i386/i386 io_apic.c local_apic.c src/sys/i386/include apicvar.h intr_machdep.h

John Baldwin jhb at
Wed Nov 2 13:21:54 PST 2005

On Wednesday 02 November 2005 03:11 pm, John Baldwin wrote:
> jhb         2005-11-02 20:11:47 UTC
>   FreeBSD src repository
>   Modified files:
>     sys/amd64/amd64      io_apic.c local_apic.c
>     sys/amd64/include    apicvar.h intr_machdep.h
>     sys/i386/i386        io_apic.c local_apic.c
>     sys/i386/include     apicvar.h intr_machdep.h
>   Log:
>   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

Forgot to mention that for now the algorithm is a very simple brain-dead one 
that just assigns each device interrupt the first free IDT vector and panics 
if all 191 are in use.

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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