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Fedora 32 mini-review on the Blackbird and Talos II


It took a little time due to hardware hijinx and the present chaos at the day job, but as is traditional, here is the regular mini-review on the latest release of Fedora (now F32) on OpenPOWER. Fedora is what we run here at Chez Floodgap/Talospace, largely because when I got my first Talos II in 2018 Fedora 28 was the only distro that worked right out of the box. However, it's also advantageous because it incorporates updates at a much faster pace than other distributions (which is why you could boot a T2 with it back then), and it's instructive because problems found here can be sorted out hopefully before they get to folks on more conservative distros. That's why I think it's worth all of us caring about it, even if you don't run it. This post is on Firefox 76 on F32.

With this release Fedora 30 progresses to end-of-life, which it hit two days ago. F31 will remain supported until F33 comes out in 6-ish months, when it too will have roughly a month's grace period before being EOLed. As before, I update Fedora manually rather than through GNOME Software. If you haven't seen the process in awhile, it looks like this:

sudo dnf upgrade --refresh # upgrade DNF
sudo dnf install dnf-plugin-system-upgrade # install upgrade plugin if not already done
sudo dnf system-upgrade download --refresh --releasever=32 # download F32 packages
sudo dnf system-upgrade reboot # reboot into upgrader

This process did not go quite as smoothly as before; two packages (that apparently were dependencies of other things) were unupgradable, and the usual --skip-broken couldn't clear the logjam, so I had to dnf remove then by hand. In addition, there is an annoying bug that started sometime in F31 where reboots seem to end up using the serial port as the console no matter what the setting is in Petitboot (you have to do a shutdown and power on instead). Fortunately, I fixed TenFourFox FPR23 to finally work properly with the new web-based BMC firmware, so I could watch the action from the Power Mac G5 using the OpenBMC's serial-to-LAN redirector (see screenshot). If you are on the console, however, for some reason the upgrader on both my Blackbird (with a naked BMC) and my T2 (with a WX7100 workstation card and the firmware in BOOTKERNFW) still reboot up to a black screen. Switch to another VTY, like CTRL-ALT-F2, and log in as root, and you can periodically issue

dnf system-upgrade log --number=-1

to watch the action. The install took a little less than an hour. It automatically restarts afterwards.

Relatively little seems to have changed in terms of system performance (on kernel 5.6.x). VLC seemed a bit quicker on my no-GPU Blackbird at pushing pixels, though mplayer is still the speed champion for media playback. Running Wayland on the Blackbird was yet again an unmitigated disaster and I have not seen any information to suggest this has changed for simple framebuffers in general (so if you're a straight BMC-only system as mine is, fuggedaboutit). On the T2, Wayland is still not as snappy as Xorg, but performance was not massively different and window theming and decorations seem more consistent. However, several games still won't launch in Wayland such as DXX, and because I'm dependent on appmodmap and there is still no equivalent feature in GNOME or Wayland to find out which window is active, Wayland on the whole remains a loss of functionality over Xorg for little gain in my book. startx forever.

If you use a lot of GNOME extensions like I do, then be prepared for some additional fallout as usual. Argos, which I use to power my little DIY IPMI fan monitor, doesn't appear to be working right in GNOME 3.36: scripts update the menu bar but their actual drop-down menus don't work, so I'll have to look into it since the maintainer isn't anymore (it looks like someone else is working on the issue, and this diff seems to fix it). Dash-to-Dock would not update properly with the GNOME tool in Firefox for a couple tries and then suddenly started working for reasons I still don't understand.

However, the worst issue was GNOME crashing every time I opened the Applications drawer. Nothing showed up under All, and if I clicked on Frequent, GNOME would either reset itself or actually force me to log out. After some poring through journalctl -e, I realized it was Appfolders Management that was the problem. Disabling that got me the apps back, and it's not really necessary anymore either since you can drag and drop apps into folders without it now. Other than modest UI changes, though, I don't notice much different about the current GNOME except that my build of Firefox Nightly now has a weirdly elongated icon in the top bar.

Overall, F32 is not a compelling release, but after a couple false starts it's working, and once I got past the usual growing pains there have been no serious problems. I'm hopeful that IBM will take a bit of a firmer hand with Red Hat and especially Fedora in the near future: I'd like OpenPOWER to finally graduate from the "alternative architectures" and be a first-class citizen with x86, which I also think will bring more attention to the port, and hopefully its niggling polish issues can be dealt with. But Wayland is still horrible without a GPU (and isn't feature-comparable with Xorg even with one), and GNOME continues to wreck its own extension ecosystem with wild abandon. Red Hat has substantial influence on these projects as many of these projects' developers work for them. Maybe we should be paying more attention there as well.

Give your OpenPOWER machine a big K1ss


This may be the wrong message in this era of COVID-19, but another operating system option for your POWER9 is to give it a big kiss. That's Kiss Linux, by the way.

Kiss Linux is an independent musl-based non-systemd distribution advertising itself as having "a focus on simplicity and the concept of less is more." Notably it uses busybox as both a source for core utilities and as init, and packages build from source a la Gentoo.

Ostensibly x86_64 only, there is an unofficial ppc64le port available specifically advertised as compatible with the Talos II and Blackbird family. A Debian netboot version is offered which can run directly from Petitboot as a staging area to do the full manual installation with a pre-compiled tarball. Although I don't see any reason why it couldn't be made to work on POWER8, the tarball is compiled for POWER9, so pre-ISA 3.0 systems will need to do more work and there doesn't seem to be current support for big-endian.

On the package side, most things seem to work. Firefox is advertised as functional, which is a good sign because that also means all of its prerequisites (rust, build system, font shaping, etc.) must also be. Netsurf is also advertised, my favourite little browser that can. However, Chromium and LibreOffice are missing, and since Kiss Linux seems to lack dbus this would also exclude GNOME. But, hey, there's no Wayland either, which is good news if you're running a system on just the BMC framebuffer.

If you're running or experimenting with giving your OpenPOWER machine a big sloppy kiss, wipe it off first (ewww), and then post in the comments.

When will OpenPOWER OpenBSD be now? Soon.


The tease of the week is this tweet from the OpenBSD maintainers, which indicates ppc64 (as "powerpc64" and implying big-endian) support is coming to OpenBSD.

It should be noted that this initial patch is very preliminary, largely just the rudiments for getting the kernel to boot, but that's more than it's done previously. It should also be noted that locore.S has dependencies on OPAL (i.e., the Open Power Abstraction Layer), which is provided by Skiboot, so pre-OpenPOWER systems like the Power Mac G5 need not apply (the G5 in particular is better served by OpenBSD/macppc). However, I don't see anything in this first pass that wouldn't work on POWER8.

When I get my "old" dual-4 Talos II up and running again this sounds like something worth experimenting with, and this would probably be the easiest route to getting NetBSD up on OpenPOWER hardware as well (my personal BSD of choice which I run on several systems currently, including a Macintosh IIci). Meanwhile, if you're going to go full Dark Helmet and want a BSD on your OpenPOWER systems that's available Now, look at FreeBSD, which is currently the most mature BSD available for our machines.

The case of the disappearing core


Here's a fun pro-tip: what do you do when one of your system's cores went out to lunch and never came back? On my original dual-4 Talos II my compile times got abnormally long and more sluggish. In dmesg I noted with alarm that it was reporting numa: Node 0 CPUs: 4-15 instead of starting at CPU 0. That means an entire core (because they're SMT-4) somehow went off-line! What gives?

The answer turns out to be related to Hostboot. The GUARD portion of the PNOR controls what hardware components have been disabled (which includes RAM sticks and individual cores), presumably due to defect, but it can also happen spuriously if Hostboot mistakes a driver glitch for actual hardware failure and erroneously turns off that component in the hardware guard entries. With main power off, a simple pflash -P GUARD -c at the BMC root prompt will clear the guard entries and indeed the prodigal core returned forthwith when I powered it back on again. Thanks to Tim Pearson at Raptor for the #protip.

#ShowUsYourTalos


Today's #ShowUsYourTalos is a Blackbird, but hey, we're all family here. Brad describes his unit thusly: "POWER9 DD2.3, 8-core; 64 GB RAM; Fractal Design Meshify C case; be quiet! Shadow Wings 2 140mm front fan; Fractal Design Dynamic X2 120mm rear fan; Silicon Power 512GB PCIe 3 NVMe 1.3 SSD; Samsung Evo 850 1TB SSD (behind motherboard); Radeon Pro WX3200 GPU; FreeBSD 13-CURRENT." Nice! We like seeing some BSD action!

If you have an OpenPOWER system you'd like to show off, post in the comments or E-mail me.

Firefox 76 on POWER


Firefox 76 is released. Besides other CSS, HTML and developer features, it refines that somewhat obnoxious zooming bar a bit, improves Picture-in-Picture further (great for livestreams: using it a lot for church), and most notably adds critical alerts for website breaches and improved password security (both generating good secure passwords and notifying you when a password used on one or other sites may have been stolen). The .mozconfigs are unchanged from Firefox 67, which is good news, because we've been stable without changing build options for quite a while at this point and we might be able to start investigating why some build options fail which should function. In particular, PGO and LTO would be nice to get working.

QEMU adds POWER10 support


"Wait," you say, "POWER10 isn't out yet!" No, it's not; even Axone (variously known as the AIO POWER9 "Advanced I/O" and "POWER9 Prime") is still yet to come out later this year (for that matter, we haven't heard much more about the LaGrange-based Raptor Condor which was announced at the same time). However, there are almost certainly simulations of the forthcoming 7nm POWER10 in IBM's chip labs, and some of that is public in the QEMU sources.

To be sure, what's currently in QEMU is at most rudimentary. The patches that have landed in the new 5.0 release describe the POWER10 as "very similar" to POWER9. The DD1.0 initial stepping (PVR base 0x00800000 as opposed to POWER9 0x004E0000) apparently introduces new ISA 3.10 (POWER9 is 3.0), though the MMU and CPU initialization code for POWER10 right now looks like a copy-pasta from the POWER9 section and doesn't expose any obvious new registers. Similarly, I can't find any IBM documentation on 3.10, so we can presume that's either under wraps or yet to be completed. However, a related commit in Skiboot drops the codename for the POWER10 machine under development: much as the POWER8 prototype was Palmetto and the POWER9 prototype was Witherspoon, POWER10's prototype is named Rainier (presumably for the mountain and not the Simpsons character). Given Axone's release expected later in 2020, the first POWER10 system descended from Rainier (like the AC922 was descended from Witherspoon) will likely not appear until 2021.

Fedora 32 released


Fedora 32 is released (changelog). We care about Fedora a lot at Talospace Low Earth Orbit HQ because it was one of the earliest distributions to run on POWER9 "out of the box" and it's what we run locally. Plus, being more bleeding edge than many distributions, even if you don't run it you should still care about it because OpenPOWER-specific issues on other distros usually get identified on Fedora first.

Given that history and that Red Hat's been an IBM property for a year and a half by now, we'd have hoped to see OpenPOWER move out of the "alternative architectures" (or at least see a little more promotion of the OpenPOWER build). That said, it's got GNOME 3.36, primarily a UX update but with a new suspend option that probably won't work on Raptor workstations anyway, TRIM by default (finally! though I turned this on in 31 anyhow), support for Free Pascal on ppc64le, gcc 10 and glibc 2.31, LLVM 10, Python 3.8 (and retirement of Python 2) and Golang 1.14. Unfortunately, 128-bit floats on ppc64le, necessary to fix some compiler and builder edge cases, have slipped deadline yet again. However, there is a semi-official workstation ISO for ppc64le now, which is welcome for new owners trying to get their machines bootstrapped.

As usual, giving a little time for the mirrors and packages to catch up, I'll try it on my basic Blackbird and Talos II and report back as we have in previous mini-reviews. Meanwhile, download it yourself if you're adventurous.

Eight four two one, twice the cores is (almost) twice as fun


It took a little while but I'm now typing on my second Raptor Talos II workstation, effectively upgrading two years in from a 32GB RAM dual quad-core POWER9 DD2.2 to a 64GB RAM dual octo-core DD2.3. It's rather notable to think about how far we've come with the platform. A number of you have asked about how this changed things in practise, so let's do yet another semi-review.

Again, I say "semi-review" because if I were going to do this right, I'd have set up both the dual-4 and the dual-8 identically, had them do the same tasks and gone back if the results were weird. However, when you're buying a $7000+ workstation you economize where you can, which means I didn't buy any new NVMe cards, bought additional rather than spare RAM, and didn't buy another GPU; the plan was always to consolidate those into the new machine and keep the old chassis, board and CPUs/HSFs as spares. Plus, I moved over the case stickers and those totally change the entire performance characteristics of the system, you dig? We'll let the Phoronix guy(s) do that kind of exacting head-to-head because I pay for this out of pocket and we've all gotta tighten our belts in these days of plague. Here's the new beast sitting beside me under my work area:

(By the way, I'm still taking candidates for #ShowUsYourTalos. If you have pictures uploaded somewhere, I'll rebroadcast them here with your permission and your system's specs. Blackbirds, POWER8s and of course any other OpenPOWER systems welcome. Post in the comments.)

This new "consolidated" system has 64GB of RAM, Raptor's BTO option Radeon WX7100 workstation GPU and two NVMe main drives on the current Talos II 1.01 board, running Fedora 31 as before. In normal usage the dual-8 runs a bit hotter than the dual-4, but this is absolutely par for the course when you've just doubled the number of processors onboard. In my low-Earth-orbit Southern California office the dual-4's fastest fan rarely got above 2100rpm while the dual-8 occasionally spins up to 2300 or 2600rpm. Similarly, give or take system load, the infrared thermometer pegged the dual-4's "exhaust" at around 95 degrees Fahrenheit; the dual-8 puts out about 110 F. However, idle power usage is only about 20W more when sitting around in Firefox and gnome-terminal (130W vs 110W), and the idle fan speeds are about the same such that overall the dual-8 isn't appreciably louder than the very quiet dual-4 was with the most current firmware (with the standard Supermicro fan assemblies, though I replaced the dual-4's PSUs with "super-quiets" a while back and those are in the dual-8 now too).

Naturally the CPUs are the most notable change. Recall that the Sforza "scale out" POWER9 CPUs in Raptor family workstations are SMT-4, i.e., each core offers four hardware threads, which appear as discrete CPUs to the operating system. My dual-4 appeared to be a 32 CPU system to Fedora; this dual-8 appears to have 64. These threads come from "slices," and SMT-4 cores have four which are paired into two "super-slices." They look like this:

Each slice has a vector-scalar unit and an address generator feeding a load-store unit. The VSU has 64-bit integer, floating point and vector ALU components; two slices are needed to get the full 128-bit width of a VMX vector, hence their pairing as super-slices. The super-slices do not have L1 cache of their own, nor do they handle branch instructions or branch prediction; all of that is per-core, which also does instruction fetch and dispatch to the slices. (This has some similar strengths and pitfalls to AMD Ryzen, for example, which also has a single branch unit and caches per core, but the Ryzen execution units are not organized in the same fashion.) The upshot of all this is that certain parallel jobs, especially those that may be competing for scarcer per-core resources like L1 cache or the branch unit, may benefit more from full cores than from threads and this is true of pretty much any SMT implementation. In a like fashion, since each POWER9 slice is not a full vector unit (only the super-slices are), heavy use of VMX would soak up to twice the execution resources though amortized over the greater efficiency vector code would offer over scalar.

The biggest task I routinely do on my T2 are frequent smoke-test builds of Firefox to make sure OpenPOWER-specific bugs are found before they get to release. This was, in fact, where I hoped I would see the most improvement. Indeed, a fair bit of it can be run parallel, so if any of my typical workloads would show benefit, I felt it would likely be this one. Before I tore down the dual-4 I put all 64GB of RAM in it for a final time run to eliminate memory pressure as a variable (and the same sticks are in the dual-8, so it's exactly the same RAM in exactly the same slot layout). These snapshots were done building the Firefox 75 source code from mozilla-release (current as of this writing) with my standard optimized .mozconfig, varying only in the number of jobs specified. I'm only reporting wall time here because frankly that's the only thing I personally cared about. All build runs were done at the text console before booting X and GNOME to further eliminate variability, and I did three runs of each configuration back to back (./mach clobber && ./mach build) to account for any caching that might have occurred. Power was measured at the UPS. Default Spectre and Meltdown mitigations were in effect.

Dual-4 (-j24)

32:22.65
31:19.17
30:49.66
average draw 170W

Dual-8 (-j48)

19:16.28
19:09.18
19:08.32
average draw 230W

Dual-8 (-j24)

19:16.46
19:13.78
19:10.14
average draw 230W

The dual-8 is approximately 40% faster than the dual-4 on this task (or, said another way, the dual-4 was about 1.6x slower), but doubling the number of make processes from my prior configuration didn't seem to yield any improvement despite being well within the 64 threads available. This surprised me, so given that the dual-8 has 16 cores, I tried 16 processes directly:

Dual-8 (-j16)

21:49.72
21:40.18
21:41.33
average draw 215W

This proves, at least for this workload, that SMT does make some difference, just not as much as I would have thought. It also argues that the sweet spot for the dual-4 might have been around -j12, but I'm not willing to tear this box back down to try it. Still, cutting down my build times by over 10 minutes is nothing to sneeze at.

For other kinds of uses, though, I didn't see a lot different in terms of performance between DD2.2 and DD2.3 and to be honest you wouldn't expect to. DD2.3 does have improved Spectre mitigations and this would help the kind of branch-heavy code that would benefit least from additional slices, but the change is relatively minor and the difference in practise indeed seemed to be minimal. On my JIT-accelerated DOSBox build the benchmarks came in nearly exactly the same, as did QEMU running Mac OS 9. Booted into GNOME as I am right now, the extra CPU resources certainly do smooth out doing more things at once, but again, that's of course more a factor of the number of cores and slices than the processor stepping.

Overall I'm pretty pleased with the upgrade, and it's a nice, welcome boost that improves my efficiency further. Here are my present observations if you're thinking about a CPU upgrade too (or are a first time buyer considering how much you should get):

  • Upgrading is pretty easy with these machines: if you bought too little today, you can always drop in a beefier CPU or two tomorrow (assuming you have the dough and the sockets), and the Self-Boot Engine code is generic such that any Sforza POWER9 chip will work on any Raptor system that can accommodate it. I have been repeatedly assured no FPGA update is needed to use DD2.3 chips, even for "O.G." T2 systems. However, if you're running a Blackbird, you should think about case and cooling as well because the 8-core will run noticeably hotter than a 4-core. A lot of the more attractive slimline mATX cases are very thermally constrained, and the 8-core CPU really should be paired with the (3U) high speed fan assembly than the (2U) passive heatsink. This is a big reason why my personal HTPC Blackbird is still a little 4-core system.

  • The 4 and 8-core chips are familiar to most OpenPOWER denizens but the 18 and 22-core monsters have a complicated value proposition. People have certainly run them in Blackbirds; my personal thought is this is courting an early system demise, though I am impressed by how heroic some of those efforts are. I wouldn't myself, however: between the thermal and power demands you're gonna need a bigger boat for these sharks.

    The T2 is designed for them and will work fine, but after my experience here one wonders how loud and hot they would get in warmer environments. Plus, you really need to fill both of those sockets or you'll lose three slots (those serviced by the second CPU's PCIe lanes), which would make them even louder and hotter. The dual-8 setup here gets you 16 cores and all of the slots turned on, so I think it's the better workstation configuration even though it costs a little more than a single-18 and isn't nearly as performant. The dual-18 and dual-22 configurations are really meant for big servers and crazy people.

    With the T2 Lite, though, these CPUs make absolute sense and it would be almost a waste to run one with anything less. The T2 Lite is just a cut-down single-socket T2 board in the same form factor, so it will also easily accommodate any CPU but more cheaply. If you need the massive thread resources of a single-18 (72 thread) or single-22 (88 thread) workstation, and you can make do with an x16 and an x8 slot, it's really the overall best option for those configurations and it's not that much more than a Blackbird board. Plus, being a single CPU configuration it's probably a lot more liveable under one's desk.

  • Simply buying a DD2.3 processor to replace a DD2.2 processor of the same core count probably doesn't pay off for most typical tasks. Unless you need the features (and there are some: besides the Spectre mitigations, it also has Ultravisor support and proper hardware watchpoints), you'll just end up spending additional money for little or no observable benefit. However, if you're going to buy more cores at the same time, then you might as well get a DD2.3 chip and have those extra features just in case you'll need them later. The price difference is almost certainly worth a little futureproofing.

What to do when the BMC won't talk to you


Normally I'm typing TenFourFox posts from the Talos II, but today I'm typing a Talospace post from the old Quad G5. When my dual-8 second T2 arrived, it turned out the onboard NICs were duds (I'm not blaming Raptor for this, mind you; crib death happens with any system). When I started moving components off it to RMA the motherboard, however, one of the RAM sticks got jammed in my old T2 and when I tried to free it, the latch not only snapped off but with such force that it struck the NIC ROM chip and knocked one of the surface mount resistors connected to it off. I will simply say that the cat fled behind the washing machine and didn't come out for hours after I realized what had happened.

That untimely accident thus left me with two systems with dead network ports, and the BMC, the heartbeat of your OpenPOWER machine, the breath of life, the starter, the prime mover, only talks on one of them. Sure, I could plug in an (ugh) USB Ethernet dongle (protip: the old TrendNET USB NIC I dug out of storage doesn't work in Petitboot, so I had to unplug and replug it when Fedora booted), or waste a PCIe slot on another NIC or whathaveyou, but none of those things restores connectivity to the BMC that for security reasons is limited to that top onboard port. The BMC is now an island unto itself, never to be updated or talked to again.

Or ... is it? The BMC fortunately has a serial port. With an easily available 10-pin to DE-9 cable which you can get on eBay for a few bucks, you can talk to your BMC again.

There's no nice web interface (I'll have a later post about how to use TenFourFox and its built-in AppleScript-to-JavaScript bridge to support its later features if you're a Power Mac refugee like me) and everything is strictly by shell, but if you were already used to talking to your BMC over SSH then this won't seem at all unfamiliar. Here it is connected to a USB serial dongle back to the G5.

In ZTerm on this G5 I set the serial connection to 115200bps, 8-N-1. Assuming your system is running the 2.00 system package or later, hit RETURN/ENTER a couple times and you should get a "Phosphor" login prompt; log in as root and your BMC password. You'll get to the root prompt just as you would over SSH.

That suffices for logging in and changing your password if necessary, but what about updating the firmware? Fortunately the clever people who maintain OpenBMC, the standard firmware in Raptor and most other OpenPOWER machines, added rz and sz to the build. That means you're just a ZMODEM upload away from updating your BMC and PNOR! Just go into the correct directory (/tmp for PNOR, /run/initramfs for the BMC firmware), run rz from the shell, and then start a ZMODEM upload from the terminal program on your assisting computer (to update the BMC, you'll upload both image-kernel and image-rofs, and to update the PNOR, whatever file as named). Some terminal programs, or the sz utility if you use it on the client side, will allow you to specify an absolute path. Either way, once it's there, you can then finish the update the usual way.

The Blackbird has such a port as well and uses the same cable as the T2 and T2 Lite. You can even leave the cable connected and this will allow you to access the BMC at any time. Note that rebooting the BMC while the main processors are still running may cause your machine to act a little funny until they're back in sync.

As a postscript, those SMT resistors are damn small, and I'm pretty sure it's not right on the pads anyway assuming I didn't damage something else in the process. But the RMA board did arrive and does work, so I'm rebuilding the new system and we'll talk about whether the jump from a dual-4 to a dual-8 T2 is worth it when I do. The old system still works otherwise and at least with that serial cable and a quad-port PCIe NIC, it may be one slot less but I can still put it to good use.

Firefox 75 on POWER


Firefox 75 seems to build uneventfully on this Raptor Talos II and as always this post is being typed in the new version. I'm not particularly enamoured of the zooming address bar and I'm sure you won't be able to turn it off eventually, but for now you can. A number of the developer-facing features are quite compelling, though. In addition, if you're on Wayland (Xorg forever), Firefox on Wayland now has H.264 VA-API and full WebGL support; I don't know how well these work on Wayland on ppc64le and I'm not going to be the one to tell you, but I'm sure some of you folks will try.

Total build time for opt on this dual-4 DD2.2 system was 36:36.67 (with -j24). Why mention it? Well, my dual-8 DD2.3 is almost here and this sounds like a convenient real-world benchmark to try out on the new box. I'm thinking -j48 sounds nice and still gives me a whole 16 threads for serious business during the compile.

The opt and debug .mozconfigs I'm using are unchanged from Firefox 67.

Some updated notes on KVMPPC


A couple quick notes on KVMPPC that came out of the last article on Mac OS 9 in QEMU:

  • If you get a kernel Oops when unloading kvm_hv, you are bitten by this bug which should be fixed in recent kernel releases. (Thanks, Paul Mackerras.)

  • However, you don't have to do that anymore to use KVM-PR anyway. With QEMU 4.2 (at least on this Talos II running Fedora 31), if you use qemu-system-ppc64 with -M accel=kvm and explicitly specify a CPU which requires KVM-PR (such as, in our previous articles, a Motorola G4/7410 with -cpu nitro), then it will be used without having to unload KVM-HV. In the examples in the second half of the article, just change qemu-system-ppc to qemu-system-ppc64 and it will now "just work" (otherwise you'll get a weird error trying to start QEMU). That is, of course, assuming you have your kernel in HPT mode instead of radix, which is the default on POWER9.

  • Likewise, if you specify -cpu host (or power8 on a POWER9), KVM-HV should be used automatically, though you can explicitly specify you want HV with -M accel=kvm,kvm-type=HV as in our AIX on OpenPOWER example. Just don't tell IBM.

If you don't understand what all that meant, read our original article for a brief primer.

Getting closer to Classic on Linux on ppc64le


A recurring theme here is my personal opinion that OpenPOWER workstations like the Raptor family (particularly now that the Blackbird is a lower-cost option) are the Power Mac successors Power Mac holdouts should embrace. It's the same processor family, it's an open system, and Raptor machines have that pride of hand-built quality and solid engineering we got accustomed to with our G4 and G5 machines. We're still missing the ability to use KVM-PR to boot Mac OS 9 in QEMU on OpenPOWER systems, but with recent improvements in QEMU and a few third-party assists, I'm now to the point where I can nevertheless use my old Mac OS 9 apps productively like FrameMaker and Photoshop 7. If you run your own QEMU builds with -O3 -mcpu=power9 performance is more than enough for these apps and you can get the work done well. In the screenshot you can see me using Photoshop to make a demo image and saving it to the shared folder, which I then opened up in GNOME's image viewer to prove it transferred over. Et voila.

There are still some pain points left (other than the lack of working KVM-PR in Mac OS 9); sound is still somewhat of a work in progress if it works at all and there is no copy-paste. Many games won't work properly either. However, QEMU Mac OS 9 guests can (with assistance) now support tablets with now much more natural mouse movement, using ndrv you can run at multiple convenient resolutions, files can be exchanged over AFP via Netatalk, and if you're willing to put up with a little clock madness QEMU can "sleep" so that you're not sucking CPU cycles in the background.

You'll need an ISO and/or CDROM of Mac OS 9 to get started. I won't provide you this and merely assume you have a perfectly legal source for one, such as ripping the installation CD you already own. (I own several.) Some of these steps I've already gone through in our earlier QEMU articles but they are reproduced here for convenience. These instructions are not OpenPOWER-specific in general and should work for other Linux systems (I'm on Fedora).

  • Create your disk image, usually qemu-img create -f qcow2 classic.img 40G or some such. We will refer to this image as classic.img in the example commands below.

  • If not already configured set up tap networking, typically with something like this for tap0, with your username being billg:

    sudo ip tuntap add dev tap0 mode tap user billg
    sudo ip link set tap0 up promisc on
    sudo brctl addif virbr0 tap0
    (optional, but handy for libvert)

    This will persist until reboot.

  • Download the custom video driver qemu_vga.ndrv from Github. I put it in ndrv/qemu_vga.ndrv.

  • Set up your initial boot string. Mine looks like this, assuming you're booting from your Mac OS 9 ISO (in iso/922.iso):

    qemu-system-ppc -M mac99,accel=tcg,via=pmu -m 1536 -drive id=root,file=classic.img,format=qcow2,l2-cache-size=4M -usb -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device rtl8139,netdev=mynet0 -rtc base=localtime -L ndrv -prom-env resolutions=640x480,800x600,1024x768,1152x864,1280x800,1440x900,1920x1080 -boot d -cdrom "iso/922.iso"

    This gives you the maximum 1.5GB of RAM Mac OS 9 supports. You'll notice we haven't enabled the tablet yet; we'll get to that.

  • Start up Mac OS 9 and install to your hard disk. When this is done, shut down the emulated Mac (QEMU will close).

  • Download our "essentials" ISO from the Floodgap gopher server (Firefox will need either OverbiteWX or OverbiteNX). It contains this USB tablet driver, the freeware 1.4 version of USB Overdrive, the Network Time control panel (for talking to RFC 868 and NTP servers) and an RTL8139 Ethernet extension. Uncompress it and bring up your system booting from the hard disk image but with the ISO ready. We'll assume it's in iso/essential.iso:

    qemu-system-ppc -M mac99,accel=tcg,via=pmu -m 1536 -boot c -drive id=root,file=classic.img,format=qcow2,l2-cache-size=4M -usb -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device rtl8139,netdev=mynet0 -rtc base=localtime -L ndrv -prom-env resolutions=640x480,800x600,1024x768,1152x864,1280x800,1440x900,1920x1080 -cdrom "iso/essential.iso"

  • Mac OS 9 should have StuffIt Expander built-in. Uncompress USB Tablet and put it in the System Folder's Startup Items (it's an app, not an INIT or CDEV). Uncompress the RTL8139 extension and put it in System Folder, Extensions. The others are optional but recommended; uncompress and install as they direct. Set your desired screen resolution of the ones available (I use 1440x900 on my 1080p display) and shut down again. Here's our last boot string change, adding the tablet this time:

    qemu-system-ppc -M mac99,accel=tcg,via=pmu -m 1536 -boot c -drive id=root,file=classic.img,format=qcow2,l2-cache-size=4M -usb -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device rtl8139,netdev=mynet0 -rtc base=localtime -L ndrv -prom-env resolutions=640x480,800x600,1024x768,1152x864,1280x800,1440x900,1920x1080 -device usb-tablet

    Incidentally, if you want to build the USB Tablet app yourself, I was able to do so by downloading the project, resource and source file, converting the .r and .c files to Mac line endings, and opening the project in CodeWarrior 7 on my MDD G4.

  • Mac OS 9 will now boot up, and once USB Tablet is run, your mouse will suddenly switch to tablet mode. No more mouse grabbing needed. Nice!

Since I have GNOME set to respond to some muscle-memory key sequences like Command-Q (to close the window), I created an appmodmap bit for QEMU so that Command-Q would be passed to the emulated Mac and only Ctrl-Command-Q would actually quit QEMU. A command like gsettings set org.gnome.desktop.wm.keybindings close "['<Ctrl><Super>Q']" & should do it too.

The next thing to do is get networking operational, because this is how we'll share files. Regular EtherTalk doesn't work but AFP-over-TCP does and Netatalk supports it. (You could of course install something like DAVE and use samba, but Mac OS 9 has AFP-over-TCP support built in and Netatalk preserves resource forks.)

  • Configure your network within Mac OS 9 from the TCP/IP control panel. As we have it configured here it should be sufficient to just get an address over DHCP (from QEMU).

  • Set up Netatalk. Depending on how it's built you may or may not get any of the authentication options to work; mine didn't with the Fedora package even though the emulated Mac could talk to my usual Sawtooth G4 fileserver with a password. I eventually just set up guest access to a single interchange folder that runs as me, because all of my office systems including the T2 are on an independent non-routable network (if you don't have such a setup, consider binding it to an internal interface only). /usr/local/etc/afp.conf thus looks like this, assuming your username is billg:

    [Global]
    ; Global server settings
        vol preset = my default values
        afp interfaces = enP4p1s0f0
        uam list = uams_guest.so
        guest account = billg

    [my default values]
        appledouble = ea
        ea = samba

    [Homes]
        basedir regex = /home

    [HFS Work Area]
        path = /home/billg/HFS

    This way some malicious Mac program (or more likely me fatfingering something) can't do anything more than trash the HFS folder from QEMU. enP4p1s0f0 is the NIC on the local network (from ip addr).

  • Go to the Chooser. Click AppleShare (notice no servers appear, even if you set AppleTalk to Ethernet) and then the Server IP Address button, and enter your host machine's local address. If you used my example above, connect as guest and you'll get offered a drive called "HFS Work Area." Open that and you will now have file sharing operational.

  • Finally, let's make it automatically mount. Since it's connected as a guest we need not preserve credentials because there are none to preserve (you could, if you wanted to, in the Mac OS 9 keychain). Make an alias of the network mount and drop it into the Servers folder in your emulated Mac's system folder. Shut down the emulated Mac and restart QEMU; the drive should automount, allowing you to instantly interchange files back and forth.

One more nice thing, which is optional, is to sleep the emulation when not in use. Sleeping from the Finder (i.e., Special, Sleep) doesn't work because the "lid is not closed" [sic], so to do this go to QEMU's Machine menu and check Pause. This does have a couple side effects, namely that after a few minutes the AppleTalk connection will be severed and the time will be wrong, since the clock doesn't resync. To reconnect the AppleTalk connection go to the Apple Menu, Recent Servers and select it; it will reopen.

The time is a little trickier. Mac OS 9 will talk to NTP servers, but it doesn't sync on demand, thus the Network Time CDEV we offered on the Essentials ISO. Not only will this let you fix the time right away (Apple Menu, Control Panels, Network Time and click Set Time) but you can also adjust for post-2002 daylight savings in your locale by defining a new, corrected timezone.

Once we figure out the issues with split-hack and KVM-PR, we should be able to get a dramatic speed boost on OpenPOWER systems. But even as it is, the software runs well and my sizeable investment in classic Mac applications is preserved. Sure, you could do this on a PC or a modern Mac, but I'd rather do it on what every Power Mac wants to be when it grows up (and when virtualization is working should be even better).

Raptor suspends shipments due to COVID-19


UPDATE from Tim Pearson: "It looks like with the latest guidance released from the state we can in fact continue to operate mostly normally. Bundles/mainboards/etc. will continue to ship from stock, but any unusual options on built systems or built systems that require parts depleted from stock would have a TBD ship date until the parts can be brought into stock." Good news! Buy that Blackbird bundle after all!

Just in case you were planning on that Blackbird: because of Illinois' "shelter-in-place" order due to the COVID-19 pandemic, Raptor is announcing they are unable to ship. Existing orders (like my order for a second dual-8 Talos II) cannot be refunded or cancelled currently, not that I plan to, but don't make the order unless you are prepared to wait. In addition, tickets and phone support are also suspended, though their IT hosting services and community support are unaffected.

Still, if you have the money to spare, we don't want these folks to go under. Maybe spin up a VM to play with.

Combat coronavirus. Buy a Blackbird.


There hasn't been a lot of content on Talospace lately because of how exponentially busier my particular dayjob has gotten and bluntly I'll just say the Chinese government has a lot to answer for the way they've handled all of this. I'm not going to belabour the obvious impact on COVID-19 on health, but it's also similarly roiling financial markets and a lot of businesses are going to fail the longer this goes on as supply chains get perturbed, especially for imported components.

Any contraction, but in particular one that has a high probability of being prolonged, is bad for niche computing markets like ours. Global contractions like the one that's hitting and the persistent one that's certain to follow disproportionately affect big-ticket items as people hold onto cash. (A finance colleague of mine is convinced there's about to be a liquidity crunch, and he makes a compelling argument I won't repeat here.) Unfortunately, largely because our sorts of systems lack various economies of scale, these are the systems most likely to die off if companies like Raptor go under because they're the ones much fewer people are buying.

This should not be interpreted as me telegraphing some belief that Raptor is financially unsound (they're a private company anyhow; I have no idea what their balance sheet looks like), but I'm rather invested in OpenPOWER and I wouldn't want it to be a casualty of the economic hit we're likely to take until a COVID-19 vaccine or effective treatment exists. And right now Raptor are the ones actually shipping workstations and I want that to continue.

I myself have already pulled the trigger on a second Talos II, upgrading to a dual-8 POWER9 DD2.3 system instead of the dual-4 DD2.2 I have now. I'll combine the RAM and cards, leaving me with a spare board, CPUs and chassis which can be a source for parts or to replace my aging POWER6 frontline server when it reaches my planned end of service period in a few years. I'm looking forward to it arriving, and I'm sure the extra few thousand would be appreciated by the back office to keep folks on the payroll getting systems configured and shipped.

If you're dithering over whether you want to pick up that Blackbird and you've got the cash or plastic on hand, consider just going ahead and doing it. Even just consider picking up a board and CPU if you need to save a little extra. Support the small businesses that support us. If this whole thing goes like we worry it's gonna, we're all going to be spending a lot more time at home anyway, so you might as well do it with a computer you can trust.

Firefox 74 on POWER


So far another uneventful release on ppc64le; I'm typing this blog post in Fx74. Most of what's new in this release is under the hood, and there are no OpenPOWER specific changes (I need to sit down with some of my other VMX/VSX patches and prep them for upstream). The working debug and optimized .mozconfigs are unchanged from Firefox 67.

Jon Masters, transparent ARM shill


I don't hate ARM. But I do hate cynical bloodymindedness.

Jon Masters' pronouncement of OpenPOWER as "dead" has been getting some press, and as far as this particular Power ISA bigot is concerned it's transparent twaddle. He's done a lot for ARM at Red Hat (lest we forget: a current subsidiary of IBM), but he's no longer at Red Hat: he's VP of Software at startup NUVIA, which is building ... a server-grade ARM chip. Knowing what he's planning on selling, that makes his "hot take" on OpenPOWER more than a little bit coloured by his own biases.

Despite being self-serving, though, not everything he points out is wrong. One valid concern is that currently the only manufacturer of high-performance OpenPOWER chips is IBM itself. We are fortunate in that Raptor is an accessible retail channel for these chips (and workstation-class systems), but most of the third-party builders are using Power in embedded applications, not high-performance desktops. Even in the Apple days the chip sources were pretty much just IBM and Motorola/Freescale, and for the G5 exclusively IBM (the brief existence of the PA6T notwithstanding); with the exception of Cell, the Power ISA game console generation was exclusively IBM too (i.e., Xenon, Gekko, Broadway and Espresso), and even Cell was an IBM co-design, so this is not a new issue. This is something that needs to be fixed and thanks to OpenPOWER being a royalty-free ISA there's a market opportunity here you don't have to pay IBM to exploit.

But to essentially argue it's okay to be open, but not that open is painfully self-serving. ARM can certainly compete in the server space; Apple's chips are already in striking distance even with their imposed limits on power consumption, and other companies have gotten into this business before. But none of them will be able to do it without paying ARM royalties, and with that investment in mind none of them want to do it without secret sauce (binary blob drivers) to deter competition. We're in a CPU age where what people think is the CPU is merely the target of a long line of intermediate operating steps and every one of these has firmware. On the Talos II I'm typing on, I can see the source code for every single boot stage. For Masters to argue that none of this matters until you pass into UEFI is like arguing that the Intel Management Engine, bless its little exposed backside, is somehow irrelevant, or that all the boot stages for POWER9 don't matter until you actually get to Petitboot, let alone all the sidecar auxiliary units like the GPEs and OCCs. Do we really need to go over again all the disastrous faults that have emerged in blackbox firmware you can't see or modify?

Masters knows this, too, and that makes his statements not just crap but disingenuous crap as well. (Perhaps he sees OpenPOWER as a threat?) Regardless, that also means you can confidently expect that NUVIA CPUs, if they ever even come out with a product (see also Calxeda), will be just as locked down as any other ARM core. So much for "reimagining silicon design."

Messing with the new 2.0 BMC


Tonight's attempt to upgrade the Blackbird to the new 2.0 BMC firmware did not go smoothly, though some of this was self-inflicted, and I'm also still flattened by whatever hellish virus has gripped me for the last month (it's not coronavirus, or at least not that coronavirus) which causes me little tolerance for glitches. TL;DR: the firmware basically works, but when I used it to reconfigure its IP address the BMC now can't see anything and nothing can see it, which has left me in somewhat of a foul mood [but see postscript]. I'll get it working when I'm feeling better and you should probably still update, but beware of these pitfalls.

Updating to 2.0 from any pre-2.0 version requires a complete flash of the BMC. Raptor warns against this generally because all your U-Boot/firmware settings will be reset, but in this case it's unavoidable. That brought us to the first problem: when sshed into the BMC, at the root prompt fw_printenv is supposed to show you the IPMI MAC address so you can reprogram it. On this Blackbird, however, it showed absolutely bupkis except for the serial port settings. After a brief moment of panic I realized I had a picture of the mainboard from the Blackbird semi-review and could enter it from that. Otherwise you'll have to drag the machine out, open it up and jot down the address printed on the board. Oddly, this does not reset anything else, including the BMC password or actual network settings. More about that in a moment. It did, however, change the ssh key.

Now updated, since my other main systems are Power Macs (and what better computer to be a "service processor" to your Blackbird than another PowerPC?), I decided to do further configuration through the BMC's new web interface in TenFourFox, which is essentially Firefox 45 with a lot of patches. These were done on my iBook G4 service laptop running the latest beta hot off the G5 in the backroom.

The first thing to keep in mind is that the certificate is self-signed. No biggie, just expect it.

The webapp appears to be written in Angular, and it's using JavaScript too recent for TenFourFox (which admittedly doesn't get along well with current React or AngularJS frameworks). Some stuff does work -- the IPMI sensor data loads -- but does not automatically update, and the server status never appeared. It might have been nicer to have a better fallback, especially for the NoScript people, so that data can be displayed even if it won't update until one reloads the page.

It didn't appear here either, even when directly queried.

Fortunately my main use case was to upload firmware through the web interface, so I decided to immediately update the PNOR (both out of necessity and as a useful test), and that worked. Just unpack the archive and upload the subarchive in the web_ipmi folder (the server will automatically unpack the .tar.gz and make the firmware available). TenFourFox threw a weird error at the end but the firmware uploaded, was verified, and could be activated.

IPL, showing the fans coming up. You can boot through the interface, but I just pushed the power button since I was sitting next to it.

The serial port output did not work on TenFourFox either, so I did it from Firefox on the MacBook Air, which I found technically disgusting but worked rather well. Fedora will happily run on the serial port. I was able to log in and look around from the BMC itself. Yes, using TenFourFox was a self-inflicted wound, but I thought it would have worked better than it did.

At this point I decided that I'd had enough mucking around with the Blackbird over WiFi and decided to give it a new static IP through the web interface and run it to the iBook over Ethernet. I did this from the Air, just in case the iBook screwed it up. The machine obligingly accepted the settings and then stopped responding on any address, even after a power cycle. Tomorrow I'll try to find a serial connector to talk to the board directly and try to start over from scratch. I would have your network settings finalized first before this update, as you probably should anyway.

I haven't tried doing this update on the Talos II. I might not anyway since my tax refund should be arriving and I'll be upgrading to a dual-8 system soon. I can't imagine there's much difference in firmware experience between the two systems, though.

The moral of the story is don't update firmware when you're ill.

POSTSCRIPT: ipmitool saves the day! After an obscure mention in an IBM technical manual I was reading for another purpose, it dawned on me that Petitboot (or, for that matter, Fedora) can set the BMC's address.

I started up the Blackbird and went into the Petitboot shell. A quick ipmitool lan print 1 showed what the problem was: the new web BMC interface claimed it had removed the old ZeroConf IP address, but had not, and that became the IP. Since the netmask was now all munged, nothing could see it and it couldn't see anything. So I forced the issue:

ipmitool lan set 1 ipsrc static
ipmitool lan set 1 ipaddr [your IPv4 address]
ipmitool lan set 1 netmask [your IPv4 netmask]
ipmitool lan set 1 defgw ipaddr 0.0.0.0

A quick powercycle confirmed it stuck, and the web BMC answers correctly on the expected address. I still consider this a bug in web BMC but fortunately it's recoverable without digging out the serial cable.

The BMC is getting new tricks


UPDATE: And it's out! Talos II, Blackbird. I'll do the Blackbird update this weekend first. The web view of the serial port (for Petitboot) is particularly nice for those of us without GPU blobs in our firmware.

On Twitter Raptor is teasing an upcoming new BMC build for all Raptor family systems (Talos II, T2 Lite and Blackbird) offering web-based environmental monitoring and firmware updates. I'm a command line jockey myself and I didn't find the previous SSH-based means too onerous, but a web-accessible environmental monitoring system could be quite useful for centralized setups (especially if there's an API or some other means to scrape the data into a dashboard). Since this data is directly served from the BMC, it would be more complete than what ibmpowernv offers now and being directly pushed should be faster than ipmitool which can take several seconds to gather information (see our DIY GNOME IPMI fan tool for a real-world example). If you can't wait, it looks like this code is publicly available in Raptor's git tree right now, but you'll have to build it yourself (you should anyway) since there don't appear to be beta builds just yet.

Firefox 73 on POWER


... seems to just work. New in this release is better dev tools and additional CSS features. This release includes the fix for certain extensions that regressed in Fx71, and so far seems to be working fine on this Talos II. The debug and optimized mozconfigs I'm using are, as before, unchanged from Firefox 67.

DIY IPMI fans


It was pointed out on the Raptor discussion board that the ibmpowernv hwmon module doesn't report fan speed for Raptor family systems, and I suspect this is true for most things based on the Romulus reference design (you can only see the fan of the graphics card, and of course only if it's installed). This means most of the GNOME shell extensions to display system status won't display it. However, it is accessible by talking to the BMC over IPMI, so you should be able to get it that way. Here's a quick-and-dirty method to put your Blackbird or T2 fan speed(s) into your GNOME shell (and probably works fine for other systems with IPMI-accessible fans). This is using Fedora 31; adjust for your distro to taste.

  1. First, verify that you do have fans. You'll need to do this as root: sudo ipmitool sdr type fan

    This will show output like this, after a couple seconds:

    fan0   | DDh | ok  | 29.1 | 2100 revolution
    fan1   | DEh | ok  | 29.2 | 2100 revolution
    fan2   | DFh | ok  | 29.3 | 1900 revolution
    fan3   | E2h | ok  | 29.4 | 2000 revolution
    fan4   | E3h | ok  | 29.5 | 1700 revolution
    fan5   | E4h | ok  | 29.6 | 1700 revolution
    fan6   | E5h | ns  | 29.7 | Disabled
    
  2. We don't want to have to constantly query the BMC as root, so create a ipmi group and put yourself in it (with vigr, vigr -s and vipw as needed). Log out and log back in, and check groups to make sure you have ipmi privileges.

  3. Create a udev rule to make IPMI group-accessible by our new group ipmi. In /etc/udev/rules.d/99_my.rules, I have

    # allow ipmi to be seen by ipmi group
    KERNEL=="ipmi*", GROUP="ipmi", MODE="0660"

    Restart your system to make sure this sticks, and/or chgrp ipmi /dev/ipmi0 ; chmod 0660 /dev/ipmi0 to make the change live. You should now be able to just do ipmitool sdr type fan as your IPMI-group user.

Now that your system is configured, let's actually integrate the output. At some point I'll maybe make this into a full-fledged extension but for prototyping and playing around purposes, there is an easier way: Argos. Though sadly the maintainer is no longer a GNOME user, the extension seems to work fine still for this purpose as of this writing.

  1. Install the Argos GNOME extension if not already done. You may wish to chmod -x ~/.config/argos/argos.sh afterwards to get the demo menu out of your menu bar.

  2. Download this simple script to format the output from ipmitool into Argos BitBar output. Its only dependencies are bash, awk and ipmitool. It gets the IPMI information, caches it (because it's expensive), and then figures out the fastest fan and puts that into the Argos button (click that for all the fans in the system, as shown in the screenshot).

  3. The script goes into ~/.config/argos, but the filename will be based on where you want it and how quickly you want it to update itself. My filename is ipmitool.6r.5s.sh, which says set it to position six on the right side of the shell bar (this varies on other shell components you have there) and updates every 5 seconds.

  4. Once you have selected position and interval, chmod +x ~/.config/argos/[filename].sh, Argos will automatically see it, and it will start updating at the interval encoded in the filename. If it's in the wrong place, or you don't like how quickly or slowly it updates, just rename the file and Argos will "do the right thing" live.

Do the brew*


I've long tried to position the Talos family as an upgrade path for Power Mac owners, and here's another way: the macOS Homebrew package manager has been ported to OpenPOWER.

The concept is a bit involved but most of the work has been done for you. To bootstrap Ruby requires building a version from the portable Ruby recipe, or you can borrow a ppc64le build and patch the vendor install script to find it. At that point you should be able to patch brew itself with the three patches linked in the instructions. We look forward to seeing these patches getting into Homebrew proper!

(*The authors of Talospace do not endorse the large-scale drinking of alcoholic beverages unless you are an Asgardian god or Australian. And even then.)

Bonuses for big-endian


As I recover from the flu and from my apoplexy over a local plumber who has stood me up for four days in a row, there's at least some good news for those of you who like big ends and cannot lie.

First, Void Linux for PowerPC reports that all available 64-bit big-endian (ppc64) and 32-bit PowerPC packages have been built, bringing them to near-parity with ppc64le. Of all total Void packages available, 32-bit ppc-musl has the lowest percentage of buildable packages, but even that is an impressively robust 88.28%. 32-bit ppc with glibc is at 88.79%, ppc64-musl at 90.15% and ppc64 at 90.49% (compare to 64-bit little-endian musl at 93.76% and glibc at 94.64%). As many 32-bit PowerPC users, particularly Power Mac owners, are looking for current supported browser options, Firefox isn't available on 32-bit (due to an xptcall issue), but WebKit and various derivatives (such as Midori and various other shells) are as well as NetSurf. (G5 owners can run Firefox on ppc64.) Chromium isn't available on any of the ports, but this seems fitting.

Secondly, someone pointed me at a distribution I hadn't encountered before called PowerEL, from VanTosh. PowerEL seems to be ultimately a Red Hat descendant and states it is ABI compatible with RHEL, but claims it derives other attributes from other distributions and has a list of repos you can browse. What I found most notable is that it offers support for big-endian POWER8 and up as well as little-endian POWER8/9 and Intel x86_64 with AVX. Note that I haven't tried booting this on a Talos II or Blackbird and it isn't clear to me how workstation-suitable it is; additionally, the internal version number suggests it's derived from RHEL 7 (not the current 8) which possibly explains why it still has big-endian support. If you use PowerEL or have tried it, post your impressions in the comments.

CentOS updated to 8.1.1911


CentOS has been updated to 8.1.1911, the distro for those of you who want Red Hat Enterprise Linux but don't want to pay for it. While not linked from the main AltArch Downloads page, ISOs that should be compatible with all OpenPOWER systems are available from the various mirrors.

Alternatively, CentOS Stream (the Freshmaker!) is also available for ppc64le.

Another Amiga you don't want


The Amigaphile community is possibly more rabid about its ecosystem than even us OpenPOWER dweebs, so right off I present my Amiga bona fides before getting stuck into it: in this house is a Amiga Technologies '060 A4000T running AmigaOS 3.9, an Amiga 3000 (with the tape drive, so I might even try Amix on it someday), and several A500s.

My disenchantment with the current crop of PowerPC-based Amigas, however, is well-known. At their various asking prices you got embedded-class CPUs at mid-high desktop level prices with performance less than a generation-old Power Mac. (Many used and easily available models of which, I might add, can run MorphOS for considerably less cash out of pocket.) A-EON's AmigaOne X5000 in particular attracts my ire for actually running a CPU that doesn't have AltiVec to replace the X1000, which did. Part of this problem was the loss of availability of the PA6T-1682M CPU, the one and only CPU P. A. Semi ever officially produced under that corporate name before Apple bought them, but there were plenty better choices than the NXP P5020 which wasn't ever really intended for this application.

Since 2014 or thereabouts a "small" Amiga (presumably along the lines of the earlier Sam440ep and Sam460ex family, which used PowerPC 400-series CPUs) was allegedly in development by A-EON and unveiled in 2015 as the original A1222 "Tabor" board. At that time it was specced as a mini-ITX board with 8GB of RAM and most controversially another grossly underpowered embedded core, a QorIQ P1022 at 1.2GHz. Based on the 32-bit e500v2 microarchitecture, it not only also lacks AltiVec but even a conventional FPU, something that for many years was not only standard on PowerPC CPUs but considered one of its particular strengths. As an embedded CPU, this was forgivable. As an embedded CPU in a modern general-purpose computing environment, however, this was unconscionable. Even by Amiga standards this was an odd choice and one with potential impacts for compatibility, and one a G5 or high-end Power Mac G4 would mop the floor with.

The original Tabor was apparently manufactured in a small batch of 50 for testers. Between then and 2018 it's not clear what happened on A-EON's end, but their hardware partner had a change of management and various other components needed updating. Strangely, the CPU was not among them. Today, six years later, people may now publicly pre-order the "A1222 Plus," with no change in specs other than changing some board components, and expected to ship Q2 2020. If you're lucky and they're not sold out, your $128 will get you a AAA Bundle Package with some software and a certificate in a pretty box as a 20 percent down payment on the "special low" $450 purchase price. If you get your $128 in after they're gone, then it's just a deposit. The AAA Bundle Package was supposed to be available December 24 but the website wasn't even up until January 11.

I'm willing to make some allowances for a cheap(er) modern Amiga because like our OpenPOWER systems, getting the price down some expands the market (ergo, Blackbird). However, that $450 price is almost certainly not the intended MSRP (nor has it been reported what that eventual MSRP is), and for low production volumes the CPU is not the major cost of a system. I don't know what actual considerations went into its design, but if A-EON chose this CPU deliberately as an attempt to make the price of the system lower, they chose wrong.

I certainly don't want to pick on other boutique systems unnecessarily. After all, in many people's minds the Talos II I'm typing on is itself a pretty darn boutique system, and one where the out-the-door price can easily eclipse even the priciest AmigaOne configuration. If people want to have their fun and pay a crapload of money for it even if other people think it's junk, then as long as it's not hurting anyone else praise the Lord and pass the credit card.

However, this is not that situation. Amiga has a long history in computing consciousness and most computer nerds would at least recognize the brand. Similarly, people still remember Power Macs, and while recollections vary in accuracy and fondness, there's a rather pernicious and commonly-held belief that Apple's migration to Intel somehow "proved" the inferiority of Power ISA. Today, along comes yet another underwhelming PowerPC-based Amiga to confirm their preconceived notions: because it's Amiga, it sticks in people's minds, and because it confirms their own beliefs about PowerPC, it reinforces their unjustified biases. Regardless of the fact that POWER9 systems like this one outpace ARM and RISC-V and compete with even high-end x86_64 offerings, the presence of Tabor and X5000 et al simply gives the resolutely underinformed yet another stick to beat Power desktops with. These Amigas suck compared to PCs, they reason, so OpenPOWER must suck too.

At the very least modern Amiga systems need to beat these decade-plus-old Power Macs to be even vaguely taken seriously. If they must go embedded then at least an e6500-series processor would do better than anything that they're running, and while I certainly do appreciate the considerable AmigaOS porting work that would be necessary, going with a minimally-redesigned reference design board for a POWER8 or POWER9 in big-endian mode could still free up development resources for such a task that would otherwise be sunk into yet another quixotic product. As it is, these Amiga systems don't do the Amiga community any favours, and from this outsider's view their performance even seems to be going backwards. If cost were the main consideration, there are other ways of dealing with it, and it's a certainty that Tabor's eventual price will be much greater than $450. Given all that, plus the protracted gestation time for "Tabor Plus," don't the Amiga owners who would be willing to buy such a machine deserve something with a little more zip?

The Amiga community needs new hardware, to be sure, and A-EON has at least filled the business opportunity however slow and abortive its progress in doing so; whatever small number they end up producing this time I imagine they'll eventually sell. That doesn't change the fact that weaksauce systems like this being sold as desktop machines continues to tar the architecture as underpowered and does nothing to expand the market beyond the shrinking circle of faithfuls. When there exist today at this very moment Power ISA workstations that can be every bit as utilitarian and functional as Intel workstations, the last thing any of our two communities need is yet another Amiga that people don't want.

Fedora Workstation Live ISOs up (and hopefully sticking)


After a little glitch getting them off the ground, Fedora Workstation Live ISOs are now a thing for ppc64le, and are exactly what they say on the tin: a try-before-you-metaphorically-buy image to check things out before you install. A bootable disk image of Rawhide (what will currently become Fedora 32) is ready now for your entertainment and possible utility, and they should turn up as a standard download presumably when F32 goes live late April.

Firefox 72 on POWER


Firefox 72 builds out of the box and uneventfully on OpenPOWER. The marquee feature this time around is picture-in-picture, which is now supported in Linux and works just fine for playing Trooper Clerks ("salsa shark! we're gonna need a bigger boat!"). The blocking of fingerprinting scripts should also be very helpful since it will reduce the amount of useless snitchy JavaScript that gets executed. The irony of that statement on a Blogger site is not lost on me, by the way.

The bug that mashed Firefox 71 (ultimately fallout from bug 1601707 and its many dupes) did not get fixed in time for Firefox 72 and turned out to be a compiler issue. The lifetime change that the code in question relies upon is in Clang 7 and up, but unless you are using a pre-release build this fix is not (yet) in any official release of gcc 9 or 10. As Clang is currently unable to completely build the browser on ppc64le, if your extensions are affected (mine aren't) you may want to add this patch which was also landed on the beta release channel for Firefox 73.

The debug and opt configurations are, again, otherwise unchanged from Firefox 67.

DOSBox JIT on ppc64le (and how you can write your own)


Apparently the quickest way to make software moar faster is to turn it into a tiny compiler and lots of things are doing it. As I get time between iterations of TenFourFox and smoke-testing Firefox builds on ppc64le, slow work on the Firefox JIT continues, but that doesn't mean we can't be JITting all the other things in the meantime.

One of my favourite games is LucasArts' Dark Forces, an FPS set in the Star Wars universe (but now apparently non-canon after the events of Rogue One). Although projects like XLEngine can run it, that, too, requires a code generator to be written (because of AngelScript). I decided that if I had to write a backend after all, a better approach would be to add a backend to DOSBox, the famous DOS emulator. That would happily run the copy of PC Dark Forces I already have and any of my other old DOS games like Extreme Pinball and Pinball Illusions and Death Rally and all those other great titles in my office besides. (The classic Mac version of Dark Forces is better, by the way, not least of which because of its beautiful high-resolution graphics that are double those of the PC release.)

Fortunately, a 32-bit big-endian PowerPC version of DOSBox already existed as unofficial patches (play it on your old Power Mac), which took only a few days for me to convert to 64-bit little-endian. While DOSBox in strictly interpreted mode on the Talos II is no slouch, this JIT, which is for DOSBox's dynamic recompiling "dynrec" core, increases performance roughly by a factor of four. This makes even the most demanding games playable and makes most other games run like butter (in fact, it's so fast it even destabilizes some timing loops, like the credits scroller in Descent). If I could shoot and take screenshots at the same time, you'd see me do better at blowing away Imperial officers, too.

You can build this yourself. Download the patch and backend, which we will call ppc64le_dosbox.diff and risc_ppc64le.h. This patch is intended to apply against SVN trunk.

svn checkout svn://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk dosbox-code-0
cd dosbox-code-0
patch -p0 < ../ppc64le_dosbox.diff
cp ../risc_ppc64le.h src/cpu/core_dynrec
./autogen.sh
./configure CFLAGS="-O3 -mcpu=power9" CXXFLAGS="-O3 -mcpu=power9"
make -j24 (or as you like)

Copy over your favourite games or install media, and src/dosbox to start your fast-powered DOS machine. Or try this benchmark pack and see for yourself. (I like the PC Player one.) See the DOSBox documentation and DOSBox wiki for more.

But let's say you'd like to work on a JIT backend of your very own for some other ppc64le port. This is hardly the place for a tutorial on writing ppc64 assembly language -- you can read IBM's -- but I will talk about how to get generated code into memory and how to execute it, and how this might differ from x86_64 or ARM. The following examples should run on any 64-bit Power CPU from the 970/G5 to the POWER9 regardless of pagesize or endianness under recent Linux kernel versions, but they're tested on my ppc64le Talos II in Fedora 31, of course.

Being able to emit generated code to memory and run it is actually a rather big security hole unless it is done carefully and correctly. Indeed, SELinux will halt you right in your tracks (as it should) unless you do the correct mating dance. The basic steps are:

  1. Allocate writeable memory.
  2. Emit machine code to that memory.
  3. Flush the caches.
  4. Make that tract of memory executable. (This is the dangerous bit. We'll talk about how to mitigate it.)
  5. Run the now executable code.
  6. Profit!

For steps 1 (and, indirectly, step 4), you need to know what the OS believes the memory page size is. (On Fedora 31, this Talos II has a pagesize of 64K. Some Linuces like Adelie use 4K pages.) For step 3, you need to know how large a cache line on your CPU is (for all current 64-bit Power ISA processors, this number is 128 bytes). We will handwave away these a bit here by keeping the example code at or less than a cache line's length, and reading the OS's page size ourselves.

Let's look at the first example. You'll notice a couple blocks of code commented out. If you are not using SELinux for whatever reason, you may be able to get away with posix_memalign() and mprotect() to allocate your memory. However, if you use this on an SELinux system (Red Hat, recent Debians, etc.), you will have to modify your policy or temporarily disable some protection features to run that code.

The better way is to create the tract of memory as an in-RAM file and use mmap() to make it writeable. This only works in integral page numbers, hence the need to know your page size (we ask the kernel via syscall). You may be able to use the second commented block to call memfd_create() directly, but the syscall approach I've used here doesn't require setting _GNU_SOURCE. Once we have mmap()ed the memory, we can write to it. We do so as simply an array of 32-bit integers (even 64-bit Power still has 32-bit opcodes).

I've ripped off the assembler macros from DOSBox's backend because they match up nicely with the numbers in the Power ISA book and pretty much any Power assembly language reference. Our first example runs a very simple program:

li 3,2020
blr

This code loads the integer 2020 into r3, the first argument register and the standard return register in the ELFv2 ABI (and indeed for any PowerPC using either PowerOpen ABI like AIX and Mac OS X, or SysV ABIs like Linux or the BSDs). It then branches back to the return address in the link register, terminating the program. We emit this code to the mmap()ed in-memory file.

The Linux kernel flushes the data and instruction caches of the processor separately, so we do the same. For every cache line that needs invalidation, we use the dcbst instruction to invalidate the data cache line in question, and once they are all flushed, we use the sync instruction so that each CPU's view of memory is consistent. Then we flush the instruction cache in the same way, using the icbi instruction and finally the isync instruction to ensure consistency of the I-cache this time. Because this all fits into a single cache line we just do each instruction once.

As our last step, we do another mmap() to make the tract of memory executable. Since we are using a named file to store our code rather than just memory we managed to grab, SELinux does not block it the same way it would ordinarily block an anonymous allocation. The second mmap() adds further security, because we are not making the memory executable until the program is fully assembled in RAM, and while the two mmap()s are linked and reference the same memory area as far as our program is concerned, assuming randomization is in effect an attacker would now have to derive two completely random memory addresses to do any funny business. We then execute the code as if were a C function (more on this in a moment).

Run the code like this:

% gcc -o jitlab1 jitlab1.c
% ./jitlab1
jitcode at 0x7fffac650000
result = 2020

Excellent! Note that the actual address of the jitcode may vary from run to run.

However, an example this trivial can only be this trivial because it didn't need to pull and manage a stack frame or maintain all but the most token adherence to the C ABI. We need a stack frame if we modify, or might modify, any non-volatile register or the link register (i.e., make any calls to other subroutines). Frankly, a JIT isn't much good if it can't call into its host somehow, either to run higher level operations or exchange data, so for all practical purposes you'll probably want to pull a stack frame in your code and be ABI compliant.

With that in mind, let's turn to our second contrived example. This slightly more complex demonstration will receive an integer value which it will perform basic math on (add 2020 to it), then call a function to display that result, double the result, and return that. As we are doing very little actual work in this JIT code (essentially messing with r3 as both the in and out argument, which is volatile, so it need not be saved in the stack frame we created), that makes control flow simpler. The function prologue, which is broken up a bit for performance reasons, can be as simple as stdu 1,-size(1):mflr 0:std 0,size+16(1), where size is the desired size of the stack frame (we use 256 here just for laziness).

Having pulled the frame and computed the first value, we now want to call the display routine to show our work. A minor complication is that there is no PowerPC/Power ISA instruction to directly branch to an address in a regular general purpose register. Instead, the ISA only supports indirect branching to either the address in the link register "LR" (blr) or the counter register "CTR" (bctr), both of which are special-purpose registers. As a practical measure, for branching other than returns from a routine, we prefer the counter register which does not need to be saved.

A more significant complication is setting up the actual function call itself. Without getting too deep into the weeds, 64-bit ELFv2 compliant functions can have two entry points, called the "global entry point" and the "local entry point." The global entry point is called when r2, the register customarily used for global symbol access through the Table of Contents, must be computed. The TOC, a holdover from PowerOpen systems, contains a conventional ELF global offset table "GOT" and optionally a small data section. The global entry point invariably consists of two instructions that compute r2 from the address of the routine itself, which is conventionally maintained in r12, and the local entry point follows at eight bytes after the global entry point. This scheme facilitates position-independent code generation as the compiler can emit code referencing globals as relative indexes on the TOC base stored in r2.

At link time the linker looks at branches and determines whether the caller function and callee function will share the same TOC. If they don't, then the linker points the branch at the global entry point either directly or through a procedure linkage table "PLT" stub. If they do, however, then this call is considered "local" (from the perspective of the global context), and the linker calls the local entry point instead. However, if it turns out the callee actually does no global access, the compiler generates only a single entry point because there is no need to compute r2, and the linker calls that.

The linker can juggle this because it has time to burn and the breadth of the codebase to scan. However, in our example here, we are the linker, and we have much less visibility into the codebase we're trying to call. Think of it as working in the basement with a flashlight trying not to walk into the walls and only a limited time to finish our job.

A hard branch (using b or bl) will always be faster, even if imperceptibly, and is less susceptible to Spectre-style attacks. However, if we actually turn out to be calling a function's global entry point and r12 is not set correctly, then r2 will also not be set correctly, and global access will either fault or just be plain wrong. If we end up doing all this computation, we might as well just branch to r12 via CTR, which is slower by a minor degree but will always work. Plus, if we're able, whatever speed hit is incurred can be mitigated by hoisting the mtctr up a few instructions ahead of the bctr or bctrl that uses it. Either way, whether we hit the global entry, the local entry or a non-global function, everything will be ABI compliant.

That does not mean you can never branch directly. Directly branching to a function with b or bl will work if you are calling a pure local function that accesses no globals, or you are calling the local entry point and nothing has modified r2 (though this is an awfully big gamble in complex codebases), or it's a function you generated (i.e., another JIT function) that you can guarantee to be purely local because it never touches r2. Or you can just set r12 and directly branch, I suppose.

The last consideration you need to keep in mind with JIT function calls is whether they need to be patchable. If they need to be patched or redirected as code addresses change, then you need to have a fixed-size branch stanza that can be changed on the fly. The minimum size of a branch stanza in 64-bit Power ISA is seven instructions (28 bytes) because we may call a 64-bit address and we need four immediate loads to compose it plus a rotation step. For example, to call a routine at 0x1234567876543210, the branch stanza looks like this:

lis 12,0x1234 (of course actually addis 12,0,0x1234)
ori 12,12,0x5678
rldicr 12,12,32,31
oris 12,12,0x7654
ori 12,12,0x3210
mtctr 12
bctrl

This yields a full 64-bit quantity, 0x1234567876543210. We can then mtctr 12 and bctrl to call the routine and come back to the generated code. Repatching this stanza is "merely" a matter of changing the bottom 16 bits of the four immediate loads and flushing the caches. You can have a direct branch in a stanza if the location of the routine is within the available displacement for those instructions, but then everything else should be nops, e.g.,

bl 0x1234567876543210
nop
(ori 0,0,0)
nop
nop
nop
nop
nop

so that if the new address no longer fits into the branch instruction's displacement, you can rewrite it as a full stanza. If you choose to set r12 and end in a hard-coded branch at the same time, remember that you'll need to repatch both things if the address changes, which might make your code generator a bit more hairy. I consider the aggressive promotion of branch stanzas to hard branches to be a form of premature optimization and you shouldn't be doing this until you are sure the rest of your code generator is working correctly.

This gets even more complex, by the way, if your JIT code must itself access globals; in that case you may need to save r2 yourself and/or do additional linkage work. I should note that in the JITs I've personally written this was never necessary. Let the C host code handle it and debugging your generated code will then be much less of a hassle.

Returning to our example, when the function call returns to the JIT code it finishes its "work," dismantles the stack frame, recovers the previous link register value and branches back to it to exit. The result remains in r3. We use decimal 1111 as our passed value in this example, so the resulting values should be 3131 (1111+2020) and 6262 (3131+3131). Since our intermediate print function helpfully returns the value it was called with, in our example here we don't need to worry about stashing it anywhere. You may not be so lucky calling someone else's work.

% gcc -o jitlab2 jitlab2.c
% ./jitlab2
jitcode at 0x7fff99dc0000
called with 3131
result = 6262

These were obviously toy examples generating small blebs of code. For code blocks greater than one cache line in size, which you will almost certainly generate, you need to dcbst (or similar) and icbi each cache line in whatever setup function gets called to flush the cache. The Z constraint we use here can make this very easy by having gcc do the work of setting up the register for each address for you. See the cache_block_closing() function in the DOSBox backend for a real-world example. In a like fashion, if your code spans multiple memory pages, with the method we have used here you will need to make each memory page writeable, and then ultimately executable, in turn.

You should also get used to tossing trap (tw 31,0,0) instructions in code blocks you're not sure about. This lets you use the debugger to verify that you actually assembled the opcodes in memory correctly and allows you to trap at the point you believe might be problematic and single-step from there. Oddly, in Fedora 31, when a trap instruction is hit gdb does pause but doesn't register a SIGTRAP (whereas lldb does seem to trap correctly, but I'm much more used to gdb personally). In this case, when the trap is sprung in gdb, you would need to press CTRL-C and induce an interrupt when the trap is hit to actually get into the debugger. Debugging JITs can be a real nightmare especially when the bug is very subtle, so only write the minimum you need to get the JIT off the ground, use traps liberally during building and never optimize prematurely. In particular ensure that your actual assembler steps that write instructions to memory are doing so accurately, as this can yield some rather humiliating issues later if you hit edge cases.

Let's make all the ppc64le things faster!