Re: [Qemu-devel] PowerPC reset vector?

["Hollis Blanchard" <hollis@penguinppc.org>]

On Sun, Dec 7, 2008 at 8:02 AM, Aurelien Jarno <aurelien@aurel32.net> wrote:
> On Sun, Dec 07, 2008 at 02:58:40PM +0200, Blue Swirl wrote:
>> Hi,
> Hi!
>
>> Currently PPC hard reset vector is 0xfffffffc for most cases. I can't
>> find this vector in the few PPC docs I have. Instead all docs point to
>> 0x00100 + base, where base can be 0xfff00000 or zero. Is the vector
>> correct?
>
> According to the PowerISA manual, the reset exception vector is the one
> you define. However on power-up, the CPU does not jump to the reset
> exception vector but instead:
> - initialize msr
> - empty all TLB
> - create a boot TLB that maps the last 4kB page in the implemented
>  effective storage address space that maps to the last 4kB page of the
>  physical address space
> - start execution of instruction at the last word address of the page
>  mapped by the boot TLB entry.

Hang on, that's not the whole story.

There are a number of supervisor-level difference between server (now
called "Book III-S") and embedded ("Book III-E") PowerPC, and this is
one of them. The behavior you describe is true for Book E, and also
happens to be true for 405 (which predates Book E and is not similar
in other respects).

However, it is *not* true for "classic" or "server" PowerPC, such as
604 or 970. Those processors reset as Blue described, with the NIP at
0xfff00100. (Actually, I think some may do even different things, like
start at 0xfff00000, but I'm not sure.)

Since qemu emulates both types of PowerPC, the reset vector must not
be hardcoded.

-Hollis