[OpenBIOS] [PATCH] ppc: force target CPU

Laurent Vivier laurent at vivier.eu
Tue Jan 19 01:50:13 CET 2016

Le 19/01/2016 00:44, Andreas Färber a écrit :
> Am 18.01.2016 um 20:14 schrieb Mark Cave-Ayland:
>> On 18/01/16 18:29, Andreas Färber wrote:
>>> Am 18.01.2016 um 07:40 schrieb Segher Boessenkool:
>>>> On Tue, Dec 29, 2015 at 04:43:09PM +0000, Mark Cave-Ayland wrote:
>>>>> After some further research, there are currently 2 reasons that make me
>>>>> feel we should be targeting earlier CPUs than the G3 for 32-bit OpenBIOS
>>>>> builds: firstly there are some people trying to emulate PPC 604 CPUs
>>>>> with QEMU/KVM which currently hangs in OpenBIOS, and secondly there has
>>>>> been talk of switching over QEMU's PReP machine from OHW to OpenBIOS
>>>>> instead.
>>>>> To that end the minimum supported CPU for PPC needs to be 602 and so
>>>>> with this in mind, I've lightly tested the attached patch which seems to
>>>>> work here - Cole, does this work on your compiler setup? If so, I think
>>>>> this is the option I would like to apply upstream.
>>>> I seriously doubt you have a 602 anywhere, or an emulator for it even.
>>>> You want 603/604, which were both called "G2".
>>> For reasons unknown to me as current maintainer, QEMU's PReP machine
>>> uses a "602" CPU model by default. We are aware of issues with that
>>> default and have overridden it from the command line occasionally in our
>>> testing, but did not reach broader agreement on why and what to change
>>> it to... so if you have more input on that...?
>>> http://git.qemu-project.org/?p=qemu.git;a=blob;f=hw/ppc/prep.c;h=0e102fcfbe01d38d939d93152921769503bc4e3a;hb=HEAD#l505
>> You can see this if you go further back in history before the files were
>> moved; it seems like Jocelyn Mayer switched to a 604 in order to fix OS/2:
>> http://git.qemu-project.org/?p=qemu.git;a=commitdiff;h=da9b266bb8491fd41badfff8ae1772007602dcca
>> and the commit where the switch appears is here, apparently in an
>> attempt to find a CPU that worked at that time:
>> http://git.qemu-project.org/?p=qemu.git;a=commitdiff;h=b37fc148bb81b5b022846156a6cba266e6c23962
> I don't really care what Jocelyn played around with. Either there was a
> real 602 based PReP machine or there wasn't. If there was, we should
> take the earliest -mcpu setting like you suggested; if there was no such
> machine, then we can fix QEMU and take up Segher's suggestion.

According to this series (from Hervé):


RS/6000 7020/40p is a PReP machine.

And according to this page:


RS/6000 7020/40p is PowerPC 601 based.


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