Re: [Qemu-devel] i8259 defaults wrong?

[Bernhard Kauer]

On Mon, Aug 17, 2009 at 04:20:24AM +0200, Herbert Poetzl wrote:
> looking at the i8259 implementation found in qemu
> as well as in the in-kernel kvm implementation, I
> see that on pic_reset() special_fully_nested_mode
> is set to zero, but the intel(r) 8259A manual says
> on page 15:
> 
>   Fully Nested Mode
>  
>   This mode is entered after initialization unless
>   another mode is programmed.
> 
> any comments are appreciated,

You confuse two modes of the PIC: the FullyNestedMode
and the SpecialFullyNestedMode. See page 18 in the
manual.

The first ist the "default" mode, where an IRQ in
service from a slave masks further interrupts from this
slave.  In SFNM a slave PIC can still issue another
IRQ.


Greetings,

        Bernhard Kauer