Saturday, April 13, 2019

PReP/40p updates

Sent the qemu patches for the upstream review. Also fixed a couple of issues in OFW: clock rush and interrupt routing for the PCNet (it still used interrupt 13, which was correct in 2017, but has been changed meanwhile).

Will update the links in the how-to shortly.

/Stay tuned

Saturday, April 6, 2019

The next How-To

Nearly 10 years after writing Solaris/SPARC under QEMU How-To, now it’s time for the AIX/PReP under QEMU How-To.

Back then my strategy was using the Power-On Self Tests and other tests from the original firmware to verify and improve qemu-system-sparc.

This time I took a different approach as some tests are synthetic and check some typical hardware-specific problems like broken and shorted wires or faulty memory chips. The result of IBM firmware diagnostics is something like “replace your motherboard” – which is not exactly helpful to find out for instance whether there is a problem with the interrupt or DMA emulation. And yeah, there are some problems with the DMA emulation, that’s why qemu-system-ppc -M 40p can not use IDE CD-ROMs under AIX, and probably some other DMA devices like sound card (haven't tried it yet).

The approach this time was making the emulation good enough and describe it the way that it

  • matches to the hardware implemented in QEMU good enough
  • has a driver in AIX

The later was tricky, as AIX does support only a very limited amount of hardware. It checks exactly that your IDE controller is from Winbond (does anyone still remember them?) and checks the exact chip model. It doesn’t care if your chip is compatible, it wants the exact match.

As result we have a -M 40p model in QEMU which is not perfectly matching the physical IBM PPS 6015, and a firmware which describes it the way AIX 5.1 can see the onboard devices.

But anyways, it was fun 10 years ago and it's still fun.

AIX/PReP under QEMU How-To

AIX/PReP under QEMU How-To

Fetch the 40p-20190406-aix-boots branch and  compile qemu-system-ppc:

configure --target-list=ppc-softmmu

download the OFW image q40pofw-serial.rom configured  for the serial line.

create an empty hard disk image:

qemu-img create -f qcow2 aix-hdd.qcow2 8G

Concerning the VGA graphics: OFW can utilize the S3-Trio emulation done by HervĂ©, but AIX 5.1 can’t use it yet. For now, the serial line rules, but if you feel adventurous you can try using it omitting  the -vga none -nongraphic part.

qemu-system-ppc -M 40p -bios q40pofw-serial.rom -serial telnet::4441,server -hda aix-hdd.qcow2 -cdrom
/path/to/aix-5.1-cd1.iso  -vga none -nographic

Then in another terminal window:
telnet localhost 4441

The following text will appear:

QEMU PReP/40p, Serial #0, 128 MiB memory installed
Open Firmware, built  April 06, 2019 17:47:55
Copyright (c) 1995-2000, FirmWorks.
Copyright (c) 2014,2017,2019 Artyom Tarasenko.

Type any key to interrupt automatic startup
Boot device: /pci/ethernet  Arguments: 
The DHCP server did not specify a boot server

Boot load failed


Once you see the “ok” prompt, type

ok boot cdrom:2
Then be patient, it takes some minutes till the first greeting appears and then some more before the installer starts.
Then answerer the installer questions. On my machine the copy process takes nearly one hour. At 93% it stalls after installing “mtools” for something like 10 Minutes, and then for another 10 minutes after “FAILURES” section, but don’t panic, eventually it will continue.

Once the install is done the emulated machine reboots to the “ok” prompt again. Type

ok boot disk

Supported AIX versions

I tested it with AIX 5.1 only. In theory it might work with 4.3.3 – 5.1 (a smoke test shows that at least the installer does start with AIX 4.3.3), let me know if you tested it. The 6015 support was officially discontinued in AIX 5.2, and probably the corresponding drivers were removed. I haven’t looked it up, as I don’t have a 5.2 media.

Networking in AIX 4.3.3 - 5.1 under QEMU

It looks like the PCNet driver (aka kent) is broken in AIX. I think the "busio" value used to look different in the previous versions. The networking can still be set up though. After performing the install, login as root and do the following (^D and ^C are Control-D and Control-C respectively):

# cat > lance-chg.asc
        name = "ent0"
        attribute = "busio"
        value = "0x01000000"
        type = "O"
        generic = "D"
        rep = "nr"
        nls_index = 3
# odmchange -o CuAt -q "name=ent0 and attribute=busio" lance-chg.asc
# rmdev -l ent0
# mkdev -l ent0
# ifconfig en0
# ping
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=255 time=4 ms
64 bytes from icmp_seq=1 ttl=255 time=3 ms

If you try it with adifferent AIX version, before changing the busio, check first whether you have to modify it:

odmget -q "name=ent0 and attribute=busio" CuAt

In case  you get

value = "0x01000000"

you don't have to change it.

Your feedback is welcome!

Last updated on 2020.02.07