Re: [Qemu-devel] [PATCH] PPC: Use correct values for 970 interrupts and hreset

[Alexander Graf]

On 28.02.2009, at 16:21, Blue Swirl wrote:

> On 2/28/09, Alexander Graf <address@hidden> wrote:
> > The 970 doesn't set exception prefix values by default. According to
> > the ISA it just jumps to real mode with nip=vector.
> >
> > Because of that the current hreset_vector is rendered invalid.  
> > Before,
> > it would go to excp_prefix (ROM base) + 0x100 (reset vector) and get
> > into the firmware.
> >
> > But with the corrected excp_prefix, we now have to jump to the real
> > entry point, which is at 0xFFFFFFFC.
>
> I don't think this is correct. 970FX uses HIOR to specify the
> exception vector base, please see "IBM PowerPC 970FX RISC
> Microprocessor", page 273.

That's only valid for LPAR, right? So it's basically a hypervisor  
register which we don't even touch, which means it's basically always 0.

Alex

> From OpenBIOS viewpoint both vectors are OK.
>
> > I can't imagine how any OS that does memory management itself could  
> > have
> > possibly worked with the code as it was.
>
> Maybe Qemu uses the 604 exception prefix somewhere.