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Re: [Qemu-ppc] [PATCH] mac99: Bring memory layout closer to real hardwar

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH] mac99: Bring memory layout closer to real hardware
Date: Mon, 14 Apr 2014 23:42:01 +0200

> Am 14.04.2014 um 23:29 schrieb Mark Cave-Ayland <address@hidden>:
> On 14/04/14 08:21, Alexander Graf wrote:
>>> I agree with adjusting the mac99 model instead of starting from
>>> scratch not only because it's less work but also because there's not
>>> much point in keeping a machine called mac99 that does not match any
>>> real Mac. I'll send my current patch with minimal changes to make the
>>> memory layout better match what's seen on PowerMac3,1.
>> I can't apply that without changing OpenBIOS as well. And OpenBIOS
>> doesn't get the memory layout from the machine, it only gets an
>> identifier that says "I'm machine numer X, use me".
>> So we would have to add a new machine type in fw_cfg for this machine,
>> as otherwise we would render newer OpenBIOS incompatible with older QEMU
>> at which point we can as well just call the whole thing a new machine.
> There is actually precedent for making simultaneous OpenBIOS and QEMU 
> changes; there have been a couple of times where the fw_cfg interface has 
> changed in the past and Blue has done simultaneous commits in order to 
> facilitate the update. Given that OpenBIOS doesn't really have a stable 
> branch as such, I'd be okay with another coordinated update during a quiet 
> OpenBIOS spell in the QEMU 2.1 development period.

If we get it done in one go and there is definite gain, sure. But I won't do 
this for thr sake of moving 5% closer to real hardware without getting there 
for real. I don't want to go through this mess again in a few months.

If we break compatibility, I would also like to *break* compatibility with real 
Macs by moving the nvram to a 64k boundary, so that the mac99 machine works 
with kvm on 64k page sized hosts.


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