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

[Andreas Färber]

Am 19.12.2010 um 16:34 schrieb 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.

No one suggested shipping proprietary firmware.

I was advocating enabling users to use the available firmware rather  
than holding fixes back just because there is no fully-working FOSS  
alternative firmware yet.

> 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 :).

We're not shipping any firmware for ppcemb either, so that argument  
seems moot. OpenBIOS, SeaBIOS and ZIPL are the only ones currently.  
Feel free to supply additional blobs for U-Boot etc.

Recent vanilla Linux kernels wouldn't run on PReP. So what Linux do  
you want to run using open source firmware?
I certainly do not intend to write firmware for the upcoming 40p  
machine. If Linux runs on real 40p hardware then it should run with  
real firmware under emulation, too. QEMU is an emulation project, not  
a Linux testing framework.

Andreas