[PATCH v2 9/9] x86: Update qemu documentation

[Soeren Moch]

On 30.07.23 19:16, Simon Glass wrote:
> Add some hints and observations related to booting distros on QEMU on x86.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
Simon,

you cc'd me on this patch (both versions), but I never used u-boot on
x86. What do you expect from my side here?

Thanks,
Soeren
> ---
>
> (no changes since v1)
>
>   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.