PRePHV - Virtualizing PReP on PowerNV
This is mostly a huge ugly hack, derived from my ppc64le_hello code. The running philosophy here is to throw things together late at night with my family asleep and see how far I get without a real design or without a real desire to implement boring things like IDE (sigh) emulation. PowerPC things though are considered fun and crucial...anyway...
It's a 64-bit LE ``hypervisor'', running a single 32-bit LE VM, with the intention of modelling some simple PReP machine...eventually hopefully enough to BSOD inside the Windows NT 4.0 PowerPC kernel. Today we pretend to be a Power Series 440 (6015) aka Sandalfoot, albeit with a 604 instead of a 601. This was an arbitrary choice, as I am nowhere near modelling any real I/O.
PReP is a long dead specification for consumer-ish PowerPC servers and workstations, that basically amounted to a pre-ACPI PC with a PowerPC CPU. Some PReP machines ran Windows NT 4.0. Most ran AIX, an obscure Solaris port, or gave Linux hackers many fun restless nights.
Relive '96... I spent that July basking on the beaches of Cagliari. Somewhere in a dusty office in Seattle people were dealing with stuff like:
Open Firmware ARC Interface Version 3.0 (Jul 12 1996 - 18:46:44) Couldn't claim SYSTEM PARAMETER BLOCK Program complete - please reboot.
Today I fake out enough of OpenFirware client interface to successfully run the VENEER.EXE ARC shim and hand off to SETUPLDR. SETUPLDR is capable of loading the setup information file, NT kernel, HAL, NLS data, setupdd.sys (the text portion of setup), the early boot drivers and hands off control to NTOSKRNL. Not much else. Specifically, the CPU VM state is not modelled quite well (or at all...?), so we panic on the kernel's attempt to set the page table base register (SDR1).
The "disk" is passed as initrd. The main achievement of crashing in NT kernel proper has been unlocked, but now I want to see some real output from the kernel to get a better sense of satisfaction ;-). Sadly, this is going to be extremely painful, because unlike the veneer and SETUPLDR, the symbols are stripped for the proper OS bits (well, separated into PDB).
You will need a LE 64-bit toolchain to build (i.e. ppc64le-linux). A good source of toolchains is kernel.org. For building skiboot (for testing) you will also need the BE 64-bit toolchain (i.e. powerpc64-linux).
Skiboot is pulled-in as a submodule. Prephv is a skiboot payload. So hypothetically it could run on a real Power8 box.
You will need Benjamin Herrenschmidt's PowerNV QEMU tree. Actually I suggest my fork of that tree, which might contain useful fixes that aren't yet present elsewhere. This is here: https://github.com/andreiw/ozbenh-qemu
Good directions for QEMU/PowerNV: https://www.flamingspork.com/blog/2015/08/28/running-opal-in-qemu-the-powernv-platform/
You now need an image.fat that contains at least the following files from the NT 4.0 CD, which are obviously not distributable:
- \veneer.exe from /PPC/VENEER.EXE
- \osloader.exe from /PPC/SETUPLDR
- \ntkrnlmp.exe from /PPC/NTKRNLMP.EXE
- \halppc.dll from /PPC/HALPPC.DLL
- \txtsetup.sif from /PPC/TXTSETUP.SIF
- *.nls from /PPC/*.NLS
- *.sys from /PPC/*.SYS
I've used FAT16. Other FAT types are untested. Good luck.
$ PPC64QEMU=/path/to/BenH/powernv/qemu make test
- Threads (+implement an interactive monitor/debugger)
- PowerISA_V2.07_PUBLIC.pdf - Book 3S
- ABI53BitOpenPOWER_21July2014_pub.pdf - ELFv2 ABI used for PPC64LE
- P8_um_external_v1.1_2015JAN29_pub.pdf - POWER8 User Manual
Andrei Warkentin (firstname.lastname@example.org).