Re: [Qemu-devel] [Qemu-ppc] [PATCH] target-ppc: Change default machine for 64-bit

[David Gibson]

On Fri, Jun 14, 2013 at 04:28:32PM +0200, Andreas Färber wrote:
> Am 13.06.2013 15:49, schrieb Alexander Graf:
> > On 17.05.2013, at 09:42, Andreas Färber wrote:
> >> Am 17.05.2013 06:25, schrieb David Gibson:
> >>> Currently, for qemu-system-ppc64, the default machine type is 'mac99'.
> >>> Since the mac99 machine is not being actively maintained, and shows quite
> >>> a few signs of bitrot,
> >>
> >> Please be more specific than making such general claims in a commit
> >> message! As the default machine it certainly compiles, so where are you
> >> seeing bitrot? The DEC bridge cleanup that I once started kind of
> >> depends on the PCI cleanup you recently looked into.
> > 
> > The mac99 machine for 64bit is actually worse than anything bitrot could 
> > give you. It emulates a machine that in its form never possibly could have 
> > existed in real hardware, which makes it very fragile and dependent on the 
> > guest's mercy to handle this gracefully.
> 
> Still we should put that in the commit message and not "shows quite a
> few signs of bitrot". Bitrot is what gus.c and cs4231a.c may have
> endured while not being compiled in or those disabled DPRINTF()s
> sprinkled all over the code base.
> 
> Further, David is looking at this from a biased perspective: -M pseries
> is best maintained (apart from e500) ppc target, but it doesn't work
> with PR KVM (not on my box anyway). But neither does mac99 on KVM due to
> page sizes or something IIRC. However under TCG either is okay with the
> guests I've seen so far and they all compile warning-free.
> 
> pseries used to hang, that is no longer the case, it just doesn't do
> anything now - still need to debug how to improve that.
> 
> > Given the current state and amount of development on the pseries
> target, I think it makes sense to declare that as the default for
> qemu-system-ppc64.
> 
> No disagreement there then.

Well, I've sent an updated version with a more accurate commit message
to Alex Graf.  It's also at git://github.com/dgibson/qemu.git,
ppc-next branch.

I do think that pseries is a better choice than mac99, but I tend to
agree with Peter Maydell that the whole notion of a default machine is
a bit silly.  In any case, since I'm no longer actively working on
qemu ppc, I don't really care enough to argue about it, so I guess
it's up to Alex.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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