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# SPDX-License-Identifier: GPL-2.0+
#
# Copyright (C) 2017, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
U-Boot on QEMU's 'virt' machine on ARM & AArch64
================================================
QEMU for ARM supports a special 'virt' machine designed for emulation and
virtualization purposes. This document describes how to run U-Boot under it.
Both 32-bit ARM and AArch64 are supported.
The 'virt' platform provides the following as the basic functionality:
- A freely configurable amount of CPU cores
- U-Boot loaded and executing in the emulated flash at address 0x0
- A generated device tree blob placed at the start of RAM
- A freely configurable amount of RAM, described by the DTB
- A PL011 serial port, discoverable via the DTB
- An ARMv7/ARMv8 architected timer
- PSCI for rebooting the system
- A generic ECAM-based PCI host controller, discoverable via the DTB
Additionally, a number of optional peripherals can be added to the PCI bus.
Building U-Boot
---------------
Set the CROSS_COMPILE environment variable as usual, and run:
- For ARM:
make qemu_arm_defconfig
make
- For AArch64:
make qemu_arm64_defconfig
make
Running U-Boot
--------------
The minimal QEMU command line to get U-Boot up and running is:
- For ARM:
qemu-system-arm -machine virt -bios u-boot.bin
- For AArch64:
qemu-system-aarch64 -machine virt -cpu cortex-a57 -bios u-boot.bin
Note that for some odd reason qemu-system-aarch64 needs to be explicitly
told to use a 64-bit CPU or it will boot in 32-bit mode.
Additional persistent U-boot environment support can be added as follows:
- Create envstore.img using qemu-img:
qemu-img create -f raw envstore.img 64M
- Add a pflash drive parameter to the command line:
-drive if=pflash,format=raw,index=1,file=envstore.img
Additional peripherals that have been tested to work in both U-Boot and Linux
can be enabled with the following command line parameters:
- To add a Serial ATA disk via an Intel ICH9 AHCI controller, pass e.g.:
-drive if=none,file=disk.img,id=mydisk -device ich9-ahci,id=ahci -device ide-drive,drive=mydisk,bus=ahci.0
- To add an Intel E1000 network adapter, pass e.g.:
-netdev user,id=net0 -device e1000,netdev=net0
- To add an EHCI-compliant USB host controller, pass e.g.:
-device usb-ehci,id=ehci
- To add a NVMe disk, pass e.g.:
-drive if=none,file=disk.img,id=mydisk -device nvme,drive=mydisk,serial=foo
These have been tested in QEMU 2.9.0 but should work in at least 2.5.0 as well.
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