Trying to get MALTA64 running under qemu

[Alexander Kabaev]

On Sun, 19 Oct 2014 15:49:56 -0700
Juli Mallett <jmallett at freebsd.org> wrote:

> On Sun, Oct 19, 2014 at 3:34 PM, Ben Morrow <ben at morrow.me.uk> wrote:
> 
> > Adrian Chadd <adrian at freebsd.org> wrote:
> > > On 18 October 2014 15:59, Ben Morrow <ben at morrow.me.uk> wrote:
> > > > I'm considering buying an ERL to use as a local router, but
> > > > before I
> > did
> > > > I thought I'd make sure the ports I want to run work properly
> > > > with
> > MIPS,
> > > > so I'm trying to bring up a qemu-system-mips64 instance. I've
> > > > built world and kernel (using MALTA64) for mips.mips64, and
> > > > built a disk
> > image
> > > > following the instructions on the MipsEmulation page on the
> > > > wiki. The source I am using is a slightly patched 10-STABLE
> > > > from 2014-09-09; the patches have nothing to do with MIPS.
> > > >
> > > > However, when I try to bring qemu up, the system appears to
> > > > hang after probing the ata devices. Over the course of about 30
> > > > seconds the qemu process goes up to 100% of one CPU, and no
> > > > more output appears on the console. This appears to happen
> > > > regardless of the disk images I pass to qemu; I've tried
> > > > passing a UFS image, a file full of zeros, no disks at all, and
> > > > (just in case) both -hda and -hdc. I've included the boot log
> > > > below; I'd appreciate any advice.
> > >
> > > can you try qemu-devel?
> >
> > Thank you, that works. (Good God, it's slow... I wonder how hard it
> > would be to replace cc with something that runs a cross-compiler on
> > the host? Maybe I can do something with distcc...)
> >
> 
> The optimal thing here is to use a user-mode emulator, whereby you can
> effectively run a MIPS userland through qemu on a FreeBSD host, so
> all of the kernel stuff is being done natively - which is a lot for
> things like package building; others have done this for ARM, and I
> believe that one of the groups using FreeBSD/MIPS was looking at
> doing so for MIPS as well for the sake of package builds, etc.  You
> might create a new thread for user-mode MIPS emulation to see if any
> of the right people notice and respond, or perhaps dig into what the
> ARM folks have done.
> 
> Thanks,
> Juli.

There is not much to it, usermode emulation for mips64 just works for
the purpose of the package building, that is how I have been doing it
for a while now. I did not get the cross-toolchain going on, but even
just running package builds under qemu-bsd-user on my amd64 machine lets
me take advantage of multiple CPUs and much less restrictive amounts of
memory and is a big win.

Five lines recipe:
1. build and install emulators/qemu-user-static port or use package
2. build and install mips64 world info some location,
say, make it /scratch/mips for the purpose of this recipe.
3. mount devfs info that image: sudo mount -t devfs
devfs /scratch/mips/dev
4. copy /usr/local/bin/qemu-mips64-static info some place within the
mips64 tree you have created
above. /scratch/mips/usr/local/bin/qemu-mips64-static will do nicely.
5. start the mips64 shell: 
sudo chroot /scratch/mips /usr/local/bin/qemu-mips64-static /bin/sh

Voila, you are running in environment that is good enough to build many
of the ports.

Now, you can start playing with installing cross-tools into that image
so that compilers/linkers are native and you do not pay the price of
emulation to run them and start writing five line recipes for others :)


-- 
Alexander Kabaev
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