use ioapic and 8259a simultaneously

[watermirror]

hi.
if it possible to use ioapic and 8259a pic simultaneously?
my bsp initialized the ioapic. but i want one ap use 8259a.
by the way, my bsp and ap run different kernel.

[Brendan]

Hi,

if it possible to use ioapic and 8259a pic simultaneously?

In theory, it is possible to use the IO APIC and PIC chips at the same time. In practice; ACPI's AML doesn't support it and it's something I'd expect to have a "higher than normal" risk of problems (e.g. motherboards that don't work properly); and the advantages (typically none) don't justify the increased complexity or the risk of potential problems.

my bsp initialized the ioapic. but i want one ap use 8259a.

I don't think that's possible. The PIC chips were never designed to support multi-CPU and I doubt there's any (reliable) way to get the PIC chip's IRQs routed to any AP.

by the way, my bsp and ap run different kernel.

In that case, if a kernel needs the PIC chips (for some unknown and likely dubious reason) then run it on the BSP, and run the kernel that uses the IO APIC on the AP. That would at least solve some of the many problems.


Cheers,

Brendan

[fluray]

Only bsp can receive 8259a interrupt request, ap will ignore it, ap only accept io apic.

[watermirror]

Only bsp can receive 8259a interrupt request, ap will ignore it, ap only accept io apic.

hi, could you tell me how could this happen?

[watermirror]

In that case, if a kernel needs the PIC chips (for some unknown and likely dubious reason) then run it on the BSP, and run the kernel that uses the IO APIC on the AP. That would at least solve some of the many problems.

hi, Brendan
could you tell me what are the problems?

[fluray]

Only bsp can receive 8259a interrupt request, ap will ignore it, ap only accept io apic.

hi, could you tell me how could this happen?

As shown in Figure:

It is bad when both open 8259 PIC and IO APIC, 8259 PIC overlapping functions with IO APIC interrupt request will be submitted twice in the BSP.
There are situations :
An interrupt request is sent to the BSP, another interrupt request is sent to AP
May cause conflicts when these interrupt handler shared variables.
...