Could we document exact steps for loongson3-virt in the manual?

["Alex Bennée" <alex.bennee@linaro.org>]

Hi,

I was trying to bootstrap a Loongson3 Debian image but ran into some
roadblocks. Philippe pointed me at:

  https://www.mail-archive.com/qemu-devel@nongnu.org/msg768848.html

which gives a bit of detail but elides over details such as how to
handle block devices. AFAICT it should support virtio-blk although maybe
Debian bullseye doesn't support the target, it's hard to say:

  ./qemu-system-mips64el -M loongson3-virt -m 4096 -nographic -blockdev driver=raw,node-name=hd0,discard=unmap,file.driver=host_device,file.filename=/dev/zvol/hackpool-0/debian-bullseye-mips64le -device virtio-blk,drive=hd0 -kernel ./vmlinuz-5.9.0-4-loongson-3 -initrd initrd.gz -append "root=/dev/sda1 console=tty0 nokaslr"

Gets as far as:

[    0.008641] printk: console [tty0] enabled
[    0.009507] printk: bootconsole [early0] disabled

and then just goes silent. It would be nice if we could add enough
detail to the appropriate target-mips.rst to:

 - give guidance on the best model to use for general purpose distros
 - describe a common command line for such
 - detail bootstraping a modern kernel

In the ARM section there is a nice "Choosing a board model" which
discusses what you want (probably "virt") and then we have varying
levels of detail for the various myriad zoo of ARM machines that are
emulated. I recently added sections to the versatile and vexpress
sections after going through similar pain trying to get those up and
running.

-- 
Alex Bennée