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Date: Sun, 7 Dec 2008 16:39:27 +0200
From: "Blue Swirl" <blauwirbel@gmail.com>
Subject: Re: [Qemu-devel] PowerPC reset vector?
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To: qemu-devel@nongnu.org

On 12/7/08, 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.

OK, I missed that part (Book III E, chapter 6.3 in PowerISA 2.05).

>  > OHW seems to depend on this extra vector, so if we change it, there
>  > may need to be some kind of compatibility hacks to let it work.
>
>
> OHW seems to follow exactly what is mapped in a real processor. OTOH, as
>  qemu and the firmware are coupled, we can probably decide that the
>  processor starts at the reset exception vector.
>
>
>  > Background: Laurent Vivier and I are trying to get OpenBIOS to work on PPC.
>
>
> Nice work. I am following the progress on openbios-devel. How close are
>  you to have a basic version working?

I get some output in the console in some cases ;-), Laurent has better versions.