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

[Simon Glass]

Hi Soeren,

On Sun, 30 Jul 2023 at 11:38, Soeren Moch <smoch at web.de> wrote:
>
> 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?

This is automatic with get_maintainers.pl but I am not sure why it added you.

Regards,
Simon

> >
> > (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.
>