Add some hints and observations related to booting distros on QEMU on x86.
Signed-off-by: Simon Glass sjg@chromium.org ---
doc/board/emulation/qemu-x86.rst | 88 ++++++++++++++++++++++++++++++-- 1 file changed, 84 insertions(+), 4 deletions(-)
diff --git a/doc/board/emulation/qemu-x86.rst b/doc/board/emulation/qemu-x86.rst index e7dd4e994d38..15f56b6bc706 100644 --- a/doc/board/emulation/qemu-x86.rst +++ b/doc/board/emulation/qemu-x86.rst @@ -113,7 +113,87 @@ sure the specified CPU supports 64-bit like '-cpu core2duo'. Conversely '-cpu pentium' won't work for obvious reasons that the processor only supports 32-bit.
-Note 64-bit support is very preliminary at this point. Lots of features -are missing in the 64-bit world. One notable feature is the VGA console -support which is currently missing, so that you must specify '-nographic' -to get 64-bit U-Boot up and running. +Booting distros +--------------- + +It is possible to install and boot a standard Linux distribution using +qemu-x86_64 by setting up a root disk:: + + qemu-img create root.img 10G + +then using the installer to install. For example, with Ubuntu 2023.04:: + + qemu-system-x86_64 -m 8G -smp 4 -bios /tmp/b/qemu-x86_64/u-boot.rom \ + -drive file=root.img,if=virtio,driver=raw \ + -drive file=ubuntu-23.04-desktop-amd64.iso,if=virtio,driver=raw + +You can also add `-serial mon:stdio` if you want the serial console to show as +well as the video. + +The output will be something like this:: + + U-Boot SPL 2023.07 (Jul 23 2023 - 08:00:12 -0600) + Trying to boot from SPI + Jumping to 64-bit U-Boot: Note many features are missing + + + U-Boot 2023.07 (Jul 23 2023 - 08:00:12 -0600) + + CPU: QEMU Virtual CPU version 2.5+ + DRAM: 8 GiB + Core: 20 devices, 13 uclasses, devicetree: separate + Loading Environment from nowhere... OK + Model: QEMU x86 (I440FX) + Net: e1000: 52:54:00:12:34:56 + eth0: e1000#0 + Hit any key to stop autoboot: 0 + Scanning for bootflows in all bootdevs + Seq Method State Uclass Part Name Filename + --- ----------- ------ -------- ---- ------------------------ ---------------- + Scanning global bootmeth 'efi_mgr': + Hunting with: nvme + Hunting with: qfw + Hunting with: scsi + scanning bus for devices... + Hunting with: virtio + Scanning bootdev 'qfw_pio.bootdev': + fatal: no kernel available + Scanning bootdev 'virtio-blk#0.bootdev': + Scanning bootdev 'virtio-blk#1.bootdev': + 0 efi ready virtio 2 virtio-blk#1.bootdev.part efi/boot/bootx64.efi + ** Booting bootflow 'virtio-blk#1.bootdev.part_2' with efi + EFI using ACPI tables at f0060 + efi_install_fdt() WARNING: Can't have ACPI table and device tree - ignoring DT. + efi_run_image() Booting /efi\boot\bootx64.efi + error: file `/boot/' not found. + +Standard boot looks through various available devices and finds the virtio +disks, then boots from the first one. After a second or so the grub menu appears +and you can work through the installer flow normally. + +Note that standard boot will not find 32-bit distros, since it looks for a +different filename. + +Current limitations +------------------- + +Only qemu-x86-64 can be used for booting distros, since qemu-x86 (the 32-bit +version of U-Boot) seems to have an EFI bug leading to the boot handing after +Linux is selected from grub, e.g. with `debian-12.1.0-i386-netinst.iso`:: + + ** Booting bootflow 'virtio-blk#1.bootdev.part_2' with efi + EFI using ACPI tables at f0180 + efi_install_fdt() WARNING: Can't have ACPI table and device tree - ignoring DT. + efi_run_image() Booting /efi\boot\bootia32.efi + Failed to open efi\boot\root=/dev/sdb3 - Not Found + Failed to load image 큀緃: Not Found + start_image() returned Not Found, falling back to default loader + Welcome to GRUB! + +The bochs video driver also seems to cause problems before the OS is able to +show a display. + +Finally, the use of `-M accel=kvm` is intended to use the native CPU's +virtual-machine features to accelerate operation, but this causes U-Boot to hang +when jumping 64-bit mode, at least on AMD machines. This may be a bug in U-Boot +or something else.