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

[Rob Landley <rob@landley.net>]

On Tuesday 04 January 2011 15:00:12 Alexander Graf wrote:
> >> I have this very issue with s390. The only host to run (and compile)
> >> this on is an s390. And few people have those. So it breaks from time to
> >> time.
> >
> > I have some pages bookmarked hinting how to get S390 Linux to boot under
> > hercules, the same way I have instructions for running m68k under Aranym.
> >  But in general, if QEMU doesn't support it I have a hard time making
> > myself care...
>
> Few people jump through the hoops to run an emulator to compile and run
> qemu inside then when they only want to verify if their patches break
> something. The general philosophy I've seen is that the best we can expect
> is a "does ./configure && make break on your x86_64 box?".

If you're talking about running qemu on a non-x86 host, I don't do that.  But 
if you're talking about running non-x86 code on qemu, my project's motto is 
"we cross compile so you don't have to".  The thing is designed so you grab a 
tarball and go "./run-emulator.sh" to get a shell prompt in your emulated 
environment, with full development tools.  If you go "./dev-environment.sh" 
instead you get a 2 gigabyte pesistent ext2 image mounted on /home so you can 
wget and build fairly large packages.

I've built the whole of Linux From Scratch 6.7 inside this this, on a couple 
different platforms.  (Still debugging powerpc and mips, probably uClibc 
issues.  Less spare time than I used to have...)

In theory I could do the same with qemu itself, just like any other software 
package.  If you feed it just one architecture in a --target-list it shouldn't 
take _too_ long to build.  But in practice running the result would be too 
slow to do more than boot to a shell prompt and demonstrate that it worked.

> > I have been know to test out of tree architecture patches, though.  I
> > only ever got sh4 to work by patching qemu, for example.
>
> I really dislike out-of-tree.

I can't stand 'em, but I don't control what gets merged into most projects.

> As soon as an architecture runs publicly
> available code, it should get upstream, so others can benefit from it.

Entirely agreed.  I've been waiting for any of the m68k improvements to QEMU 
(to run more than just coldfire) work to get merged for a long time.  And I 
have a todo item to look at https://github.com/uli/qemu-s390 also...

> Alex

Rob
-- 
GPLv3: as worthy a successor as The Phantom Menace, as timely as Duke Nukem 
Forever, and as welcome as New Coke.