qemu/pc-bios/README
Alexey Kardashevskiy fc8c745d50 spapr: Implement Open Firmware client interface
The PAPR platform describes an OS environment that's presented by
a combination of a hypervisor and firmware. The features it specifies
require collaboration between the firmware and the hypervisor.

Since the beginning, the runtime component of the firmware (RTAS) has
been implemented as a 20 byte shim which simply forwards it to
a hypercall implemented in qemu. The boot time firmware component is
SLOF - but a build that's specific to qemu, and has always needed to be
updated in sync with it. Even though we've managed to limit the amount
of runtime communication we need between qemu and SLOF, there's some,
and it has become increasingly awkward to handle as we've implemented
new features.

This implements a boot time OF client interface (CI) which is
enabled by a new "x-vof" pseries machine option (stands for "Virtual Open
Firmware). When enabled, QEMU implements the custom H_OF_CLIENT hcall
which implements Open Firmware Client Interface (OF CI). This allows
using a smaller stateless firmware which does not have to manage
the device tree.

The new "vof.bin" firmware image is included with source code under
pc-bios/. It also includes RTAS blob.

This implements a handful of CI methods just to get -kernel/-initrd
working. In particular, this implements the device tree fetching and
simple memory allocator - "claim" (an OF CI memory allocator) and updates
"/memory@0/available" to report the client about available memory.

This implements changing some device tree properties which we know how
to deal with, the rest is ignored. To allow changes, this skips
fdt_pack() when x-vof=on as not packing the blob leaves some room for
appending.

In absence of SLOF, this assigns phandles to device tree nodes to make
device tree traversing work.

When x-vof=on, this adds "/chosen" every time QEMU (re)builds a tree.

This adds basic instances support which are managed by a hash map
ihandle -> [phandle].

Before the guest started, the used memory is:
0..e60 - the initial firmware
8000..10000 - stack
400000.. - kernel
3ea0000.. - initramdisk

This OF CI does not implement "interpret".

Unlike SLOF, this does not format uninitialized nvram. Instead, this
includes a disk image with pre-formatted nvram.

With this basic support, this can only boot into kernel directly.
However this is just enough for the petitboot kernel and initradmdisk to
boot from any possible source. Note this requires reasonably recent guest
kernel with:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df5be5be8735

The immediate benefit is much faster booting time which especially
crucial with fully emulated early CPU bring up environments. Also this
may come handy when/if GRUB-in-the-userspace sees light of the day.

This separates VOF and sPAPR in a hope that VOF bits may be reused by
other POWERPC boards which do not support pSeries.

This assumes potential support for booting from QEMU backends
such as blockdev or netdev without devices/drivers used.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20210625055155.2252896-1-aik@ozlabs.ru>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
[dwg: Adjusted some includes which broke compile in some more obscure
 compilation setups]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2021-07-09 10:38:19 +10:00

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- SeaBIOS (bios.bin) is the successor of pc bios.
See http://www.seabios.org/ for more information.
- The VGA BIOS and the Cirrus VGA BIOS come from the LGPL VGA bios
project (http://www.nongnu.org/vgabios/).
- OpenBIOS (http://www.openbios.org/) is a free (GPL v2) portable
firmware implementation. The goal is to implement a 100% IEEE
1275-1994 (referred to as Open Firmware) compliant firmware.
The included images for PowerPC (for 32 and 64 bit PPC CPUs),
Sparc32 (including QEMU,tcx.bin and QEMU,cgthree.bin) and Sparc64 are built
from OpenBIOS SVN revision 1280.
- SLOF (Slimline Open Firmware) is a free IEEE 1275 Open Firmware
implementation for certain IBM POWER hardware. The sources are at
https://github.com/aik/SLOF, and the image currently in qemu is
built from git tag qemu-slof-20210217.
- VOF (Virtual Open Firmware) is a minimalistic firmware to work with
-machine pseries,x-vof=on. When enabled, the firmware acts as a slim shim and
QEMU implements parts of the IEEE 1275 Open Firmware interface.
- sgabios (the Serial Graphics Adapter option ROM) provides a means for
legacy x86 software to communicate with an attached serial console as
if a video card were attached. The master sources reside in a subversion
repository at http://sgabios.googlecode.com/svn/trunk. A git mirror is
available at https://gitlab.com/qemu-project/sgabios.git.
- The PXE roms come from the iPXE project. Built with BANNER_TIME 0.
Sources available at http://ipxe.org. Vendor:Device ID -> ROM mapping:
8086:100e -> pxe-e1000.rom
8086:1209 -> pxe-eepro100.rom
1050:0940 -> pxe-ne2k_pci.rom
1022:2000 -> pxe-pcnet.rom
10ec:8139 -> pxe-rtl8139.rom
1af4:1000 -> pxe-virtio.rom
- The sources for the Alpha palcode image is available from:
https://github.com/rth7680/qemu-palcode.git
- The u-boot binary for e500 comes from the upstream denx u-boot project where
it was compiled using the qemu-ppce500 target.
A git mirror is available at: https://gitlab.com/qemu-project/u-boot.git
The hash used to compile the current version is: 2072e72
- Skiboot (https://github.com/open-power/skiboot/) is an OPAL
(OpenPower Abstraction Layer) firmware for OpenPOWER systems. It can
run an hypervisor OS or simply a host OS on the "baremetal"
platform, also known as the PowerNV (Non-Virtualized) platform.
- QemuMacDrivers (https://github.com/ozbenh/QemuMacDrivers) is a project to
provide virtualised drivers for PPC MacOS guests.
- The "edk2-*.fd.bz2" images are platform firmware binaries and matching UEFI
variable store templates built from the TianoCore community's EFI Development
Kit II project
<https://github.com/tianocore/tianocore.github.io/wiki/EDK-II>. The images
were built at git tag "edk2-stable202008". The firmware binaries bundle parts
of the OpenSSL project, at git tag "OpenSSL_1_1_1g" (the OpenSSL tag is a
function of the edk2 tag). Parts of the Berkeley SoftFloat library are
bundled as well, at Release 3e plus a subsequent typo fix (commit
b64af41c3276f97f0e181920400ee056b9c88037), as an OpenSSL dependency on 32-bit
ARM. Licensing information is given in "edk2-licenses.txt". The image files
are described by the JSON documents in the "pc-bios/descriptors" directory,
which conform to the "docs/interop/firmware.json" schema.
- OpenSBI (https://github.com/riscv/opensbi) aims to provide an open-source
reference implementation of the RISC-V Supervisor Binary Interface (SBI)
specifications for platform-specific firmwares executing in M-mode. For all
supported platforms, OpenSBI provides several runtime firmware examples.
These example firmwares can be used to replace the legacy riscv-pk bootloader
and enable the use of well-known bootloaders such as U-Boot.
OpenSBI is distributed under the terms of the BSD 2-clause license
("Simplified BSD License" or "FreeBSD License", SPDX: BSD-2-Clause). OpenSBI
source code also contains code reused from other projects desribed here:
https://github.com/riscv/opensbi/blob/master/ThirdPartyNotices.md.
- npcm7xx_bootrom.bin is a simplified, free (Apache 2.0) boot ROM for Nuvoton
NPCM7xx BMC devices. It currently implements the bare minimum to load, parse,
initialize and run boot images stored in SPI flash, but may grow more
features over time as needed. The source code is available at:
https://github.com/google/vbootrom