General Information
===================

This is ski: an ia64 instruction set simulator

This repository is a fork of:
  http://ski.sourceforge.net

The license is GPL-2.

Installation
============

See the file 'INSTALL'

Running
=======

Running Ski requires a few moving parts:

1. build ski-specific linux kernel
2. prepare disk image of a file system
3. run ski

1. Building kernel

The caveat is that upstream removed Ski-specific bits from linux-5.0.
Thus latest supported kernel by Ski is 4.19 (see TODOs to get Ski ported
to newer kernels).

Once you get ia64-unknown-linux cross-compiler toolchain it is
straightforward:

    $ wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.19.241.tar.xz
    $ tar -xf linux-4.19.241.tar.xz
    $ cd linux-4.19.241
    $ ARCH=ia64 CROSS_COMPILE=ia64-unknown-linux-gnu- make sim_defconfig
    $ ARCH=ia64 CROSS_COMPILE=ia64-unknown-linux-gnu- make -j$(nproc)

The toolchain versions I used to get working setup are:
- gcc-11.3.0
- binutils-2.36

Newer ones should work as well.

2. Preparing disk image

That can be any filesystem supported by guest kernel. sim_defconfig
supports ext2 as is. I used fresh Gentoo image to verify it:

    $ wget https://bouncer.gentoo.org/fetch/root/all/releases/ia64/autobuilds/20220420T025349Z/stage3-ia64-systemd-20220420T025349Z.tar.xz
    $ dd of=sdc if=/dev/zero bs=512 count=10485760 #5G
    $ /sbin/mke2fs sdc
    $ mkdir mnt
    $ mknod /dev/loop0 b 7 0
    $ mount -t ext2 -oloop sdc ./mnt
    $ cd mnt
    $ tar -xpf ../stage3-ia64-systemd-20220420T025349Z.tar.xz
    # ignore dev creation failures
    $ cd ..
    $ umount mnt

Here we created `sdc` file and populated it with contents of `stage3`.

3. Running Ski

Once you have got the bits it should just run:

    $ bski linux-4.19.241/arch/ia64/hp/sim/boot/bootloader linux-4.19.241/vmlinux root=/dev/sda simscsi=./sd simeth=eth0 init=/bin/bash PATH=/bin rw
    ...
    loading linux-4.19.241/vmlinux...
    starting kernel...
    Linux version 4.19.241 (root@gentoo) (gcc version 11.3.0 (Gentoo 11.3.0 p4)) #1 SMP PREEMPT Tue May 3 23:52:46 BST 2022
    ...
    root@(none) / # mount -t proc proc /proc
    root@(none) / # uname -a
    Linux (none) 4.19.241 #1 SMP PREEMPT Tue May 3 23:52:46 BST 2022 ia64 McKinley HP Ski Simulator GNU/Linux
    root@(none) / # cat /proc/cpuinfo
    processor  : 0
    vendor     : HP Ski Simulator
    arch       : IA-64
    family     : 31
    model      : 0
    model name : McKinley
    revision   : 0
    archrev    : 0
    features   : branchlong, 16-byte atomic ops
    cpu number : 0
    cpu regs   : 4
    cpu MHz    : 2.000
    itc MHz    : 2.000000
    BogoMIPS   : 1.23
    siblings   : 1

Fork-specific notes
===================

The goal of this fork is to keep ski running on modern
systems. This include but is not limited to:

- pulling in downstream distribution patches
- updating dynamic translator code to work on
  modern linux

New additions:
- Experimental minimal UART8250 console output. Can be used with the
  following setup:
    * kernel .config:
      CONFIG_SERIAL_EARLYCON=y
      CONFIG_SERIAL_8250=y
      CONFIG_SERIAL_8250_CONSOLE=y
    * kernel parameters:
      earlycon=uart8250,mmio,0xff5e0000
  TODOs:
    * port bootloader over to earlycon to get visible output for
      CONFIG_HP_SIMSERIAL_CONSOLE=n kernels.
    * export UART1/UART2 via some interface (hcdp? SPCR?) to make it
      usable as a promary console after early boot as well.

General software support for ia64
=================================

Last versions supported by the toolchain:

- `glibc-2.38`, removed in <https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=460860f457e2a889785c506e8c77d4a7dff24d3e>
- `linux-6.6`, removed in <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cf8e8658100d4eae80ce9b21f7a81cb024dd5057>
- `gcc-13`, still not removed as of 2024-01-08
- `binutils-2.41`, still not removed as of 2024-01-08

TODOs
=====

- Port from ski-specific virtual devices to more standard VIRTIO:
  * simcons -> virtio-console
  * simscsi -> virtio-blk
  * simeth  -> virtio-net

- Bring CPU emulator up to the state where we could include it in qemu
  * Currently CPU emulator uses global state for various things. It's
    not very reusable as is.

- stop requiring 'bootloader' and be able to run unmodified ia64 kernel
  * plumb EFI mapping
  * plumb ACPI space
  * plumb PCI space
  * add support for initramfs loading

- covert doc/ documentation into something closer to plain text