Emulated macppc with qemu

[Havard Eidnes <he%NetBSD.org@localhost>]

Hi,

after a bit of trial and error, I now have an emulated macppc
host up and running with qemu.  This appears to require qemu
5.2.0 (latest from pkgsrc).

The script I've used to start and run the installer with is

---
#!/bin/sh

MEM=2g
qemu-system-ppc \
        -M mac99,via=pmu \
        -m $MEM  \
        -nographic \
        -drive id=hda,format=raw,file=disk.img \
        -L pc-bios \
        -netdev user,id=net0,hostfwd=tcp::2223-:22,ipv6=off \
        -net nic,model=rtl8139,netdev=net0 \
        -boot d \
        -cdrom NetBSD-8.2-macppc.iso
---

The installer is booted up with "boot cd:\ofwboot.xcf".

There appears to be something finicky about the amount of memory:
1G fails with a trap early on, 3G fails as described in

  https://bugs.launchpad.net/bugs/1922391

quite a bit into the installation, but with 2G I've managed to
install and it appears to run stably as well.

I recently built a pared-down kernel for one of my G4 Mac Minis,
and that system has 1G physical memory and runs fine, while if I
try the same 5.2MB-sized kernel in qemu, it still fails when only
configured with 1G memory.  There's something spooky going on
here, I think...

It also appears that the ppc qemu doesn't support SMP, at least
not in this version.

Speed-wise it's nothing to write home about, but it's not
entirely unusable either: a 1.5GHz G4 Mac Mini gives this with
"openssl speed sha1":

type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
sha1              5365.74k    19695.50k    64076.54k   146566.70k   235167.74k

while the emulated system on a i7-4790 host gives

type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
sha1              1123.70k     4264.97k    15203.62k    40735.26k    86124.15k

Regards,

- Håvard