[PATCH 1/4] conf: add loader type 'none'

[Andrea Bolognani]

On Tue, Apr 11, 2023 at 01:14:27PM +0200, Gerd Hoffmann wrote:
> > The second approach is the one described in the Ubuntu wiki[3], and
> > also requires passing two files to QEMU, except this time they come
> > from the opensbi and u-boot-qemu packages respectively. The usage
> > looks like
> >
> >   -bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf
> >   -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf
> >
> > I think in this case the first file is a minimal build of OpenSBI
> > that likely just initializes enough hardware before handing control
> > to an arbitrary payload - in this case, u-boot.
>
> Yes.  These days opensbi seems to be loaded by default, so the first
> line is not needed.  In fact I'm running a guest here, on fedora 37 +
> virt-preview with just this ...
>
>   <os>
>     <type arch='riscv64' machine='virt'>hvm</type>
>     <kernel>/home/kraxel/projects/u-boot/build-qemu-riscv64-smode/u-boot.bin</kernel>
>     <boot dev='hd'/>
>   </os>
>
> ... and it works fine.

This matches my experience.

I've tried both u-boot.bin (referenced in openSUSE and FreeBSD
documentation) and uboot.elf (Debian and Ubuntu documentation) and it
doesn't seem to make a difference which one you choose.

> There is also this variant ...
>
>   <qemu:commandline>
>     <qemu:arg value='-drive'/>
>     <qemu:arg value='if=pflash,index=1,format=raw,file=/vmdisk/hdd/pool-risc-v/RISCV_VIRT.raw'/>
>   </qemu:commandline>
>
> ... to boot edk2 firmware.  Note this is a single image carrying both
> code and vars.  Also note 'index=1', which I think is needed because the
> (default) opensbi is loaded to the pflash device with 'index=0'.
>
> This doesn't boot the distro due to grub2 not having full riscv64 efi
> support (yet).

The openSUSE images are using grub2, and possibly EFI somehow?

Right after selecting the entry I see

  EFI stub: Booting Linux Kernel...
  EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path
  EFI stub: Using DTB from configuration table
  EFI stub: Exiting boot services...

The image never manages to boot all the way for me: it looks like it
can't find the root filesystem. But eventually I get dropped into a
rescue shell, and /sys/firmware/efi/ contains some data.

Note that I'm not using edk2 in this case, just the same u-boot.bin
file that I've used to boot other images.

-- 
Andrea Bolognani / Red Hat / Virtualization