ppce500 generic platform (`ppce500`)

QEMU for PPC supports a special ppce500 machine designed for emulation and virtualization purposes.

Supported devices

The ppce500 machine supports the following devices:

PowerPC e500 series core (e500v2/e500mc/e5500/e6500)
Configuration, Control, and Status Register (CCSR)
Multicore Programmable Interrupt Controller (MPIC) with MSI support
1 16550A UART device
1 Freescale MPC8xxx I2C controller
1 Pericom pt7c4338 RTC via I2C
1 Freescale MPC8xxx GPIO controller
Power-off functionality via one GPIO pin
1 Freescale MPC8xxx PCI host controller
VirtIO devices via PCI bus
1 Freescale Enhanced Triple Speed Ethernet controller (eTSEC)

Hardware configuration information

The ppce500 machine automatically generates a device tree blob (“dtb”) which it passes to the guest, if there is no -dtb option. This provides information about the addresses, interrupt lines and other configuration of the various devices in the system.

If users want to provide their own DTB, they can use the -dtb option. These DTBs should have the following requirements:

The number of subnodes under /cpus node should match QEMU’s -smp option
The /memory reg size should match QEMU’s selected ram_size via -m

Both qemu-system-ppc and qemu-system-ppc64 provide emulation for the following 32-bit PowerPC CPUs:

e500v2
e500mc

Additionally qemu-system-ppc64 provides support for the following 64-bit PowerPC CPUs:

e5500
e6500

The CPU type can be specified via the -cpu command line. If not specified, it creates a machine with e500v2 core. The following example shows an e6500 based machine creation:

$ qemu-system-ppc64 -nographic -M ppce500 -cpu e6500

Boot options

The ppce500 machine can start using the standard -kernel functionality for loading a payload like an OS kernel (e.g.: Linux), or U-Boot firmware.

When -bios is omitted, the default pc-bios/u-boot.e500 firmware image is used as the BIOS. QEMU follows below truth table to select which payload to execute:

-bios	-kernel	payload
N	N	u-boot
N	Y	kernel
Y	don’t care	u-boot

When both -bios and -kernel are present, QEMU loads U-Boot and U-Boot in turns automatically loads the kernel image specified by the -kernel parameter via U-Boot’s built-in “bootm” command, hence a legacy uImage format is required in such scenario.

Running Linux kernel

Linux mainline v5.11 release is tested at the time of writing. To build a Linux mainline kernel that can be booted by the ppce500 machine in 64-bit mode, simply configure the kernel using the defconfig configuration:

$ export ARCH=powerpc
$ export CROSS_COMPILE=powerpc-linux-
$ make corenet64_smp_defconfig
$ make menuconfig

then manually select the following configuration:

Platform support > Freescale Book-E Machine Type > QEMU generic e500 platform

To boot the newly built Linux kernel in QEMU with the ppce500 machine:

$ qemu-system-ppc64 -M ppce500 -cpu e5500 -smp 4 -m 2G \
    -display none -serial stdio \
    -kernel vmlinux \
    -initrd /path/to/rootfs.cpio \
    -append "root=/dev/ram"

To build a Linux mainline kernel that can be booted by the ppce500 machine in 32-bit mode, use the same 64-bit configuration steps except the defconfig file should use corenet32_smp_defconfig.

To boot the 32-bit Linux kernel:

$ qemu-system-ppc64 -M ppce500 -cpu e500mc -smp 4 -m 2G \
    -display none -serial stdio \
    -kernel vmlinux \
    -initrd /path/to/rootfs.cpio \
    -append "root=/dev/ram"

Running U-Boot

U-Boot mainline v2021.07 release is tested at the time of writing. To build a U-Boot mainline bootloader that can be booted by the ppce500 machine, use the qemu-ppce500_defconfig with similar commands as described above for Linux:

$ export CROSS_COMPILE=powerpc-linux-
$ make qemu-ppce500_defconfig

You will get u-boot file in the build tree.

When U-Boot boots, you will notice the following if using with -cpu e6500:

CPU:   Unknown, Version: 0.0, (0x00000000)
Core:  e6500, Version: 2.0, (0x80400020)

This is because we only specified a core name to QEMU and it does not have a meaningful SVR value which represents an actual SoC that integrates such core. You can specify a real world SoC device that QEMU has built-in support but all these SoCs are e500v2 based MPC85xx series, hence you cannot test anything built for P4080 (e500mc), P5020 (e5500) and T2080 (e6500).

Networking

By default a VirtIO standard PCI networking device is connected as an ethernet interface at PCI address 0.1.0, but we can switch that to an e1000 NIC by:

$ qemu-system-ppc64 -M ppce500 -smp 4 -m 2G \
                    -display none -serial stdio \
                    -bios u-boot \
                    -nic tap,ifname=tap0,script=no,downscript=no,model=e1000

The QEMU ppce500 machine can also dynamically instantiate an eTSEC device if “-device eTSEC” is given to QEMU:

-netdev tap,ifname=tap0,script=no,downscript=no,id=net0 -device eTSEC,netdev=net0

Root file system on flash drive

Rather than using a root file system on ram disk, it is possible to have it on CFI flash. Given an ext2 image whose size must be a power of two, it can be used as follows:

$ qemu-system-ppc64 -M ppce500 -cpu e500mc -smp 4 -m 2G \
    -display none -serial stdio \
    -kernel vmlinux \
    -drive if=pflash,file=/path/to/rootfs.ext2,format=raw \
    -append "rootwait root=/dev/mtdblock0"

ppce500 generic platform (ppce500)