[Qemu-devel] Re: [PATCH 0/4] ppc: Fix PReP emulation

[Alexander Graf]

On 19.12.2010, at 16:04, Andreas Färber wrote:

> Am 19.12.2010 um 10:54 schrieb Alexander Graf:
> 
>> On 14.12.2010, at 01:49, Andreas Färber wrote:
>> 
>>> Hello,
>>> 
>>> Based on an earlier attempt of mine to make OpenBIOS work with -M prep,
>>> with kind support from Hervé Poussineau here's an initial stab at
>>> fixing the long-broken PReP emulation and preparing migration from
>>> abandoned OpenHack'Ware to OpenBIOS as default FOSS firmware.
>>> 
>>> In particular a number of hw_error()s are resolved, so that the BIOS
>>> can be entered at all. It is not yet working in terms of serial and
>>> VGA support etc.
>>> 
>>> This series is also available from:
>>> 
>>> git://repo.or.cz/qemu/afaerber.git prep-queue
>>> 
>>> Some more work-in-progress for the curious is on my prep branch [2].
>>> The corresponding work-in-progress OpenBIOS changes are at [3].
>>> 
>>> Unfortunately the prep machine is lacking documentation what exactly it
>>> tries to emulate. The plan thus is to merge emulation of a second, real
>>> IBM 40p machine based on Hervé's work at [1], for use with original
>>> binary firmware.
>>> 
>>> Also upcoming are new ppc_chrp machines, forked from ppc_newworld,
>>> emulating the 970-based IBM JS20 (using Apple U3) [4] and possibly the
>>> POWER5-based IntelliStation 285. These depend on the ongoing ppc64 port
>>> of OpenBIOS to be completed though. This relates to PReP in that the
>>> machine IDs will need to be coordinated.
>> 
>> Does this series actually make anything work, or is it just a first step set 
>> to get your development rolling? IOW, would users benefit from having the 
>> patches upstream yet?
> 
> As indicated above, it lets you enter a BIOS, which is a user-visible 
> improvement. User-supplied binary firmware works with 1 + 3-4, ELF firmware 
> with 1-4. Patch 3 depends on review comments. Patch 4 was just an FYI for 
> testing the preceding patches and still needs investigation.
> 
> For OpenBIOS to work, we need fw_cfg in ppc_prep.c and, independently, 
> patches to OpenBIOS. Unless of course we want to use another firmware like 
> OFW from the start. The main interest in PReP nowadays will be proprietary 
> firmware anyway. I thought Rob (cc'ed) had PReP Linux kernel patches for QEMU 
> at some point but I couldn't locate them in the Aboriginal Linux tree.

I'm not sure on the copyright problems we might run into when delivering binary 
firmware. So we certainly do need some open source firmware solution for prep 
to at least have Linux running. For other guests, I don't see a reason why 
users shouldn't try to fetch a real firmware blob separately :).

> 
> I am planning to queue reviewed patches for upstream on a new branch. Then we 
> can either pull them into your ppc queue or directly into master.

I'd say let's wait until we get to a point where we can boot any (really, any) 
guest. As soon as we're there, let's pull the whole thing in to qemu. Until 
then, I'm sure little enough code changes upstream that it's fine to keep it in 
a separate tree.

If it gets too cumbersome to keep it separate, just nag me and I'll reconsider 
:).


Alex