run_qemu.sh: replace -drive rootfs with -blockdev + -device

[marc-hb]

According to Itaru Kitayama in #210, this fixes the following error:

  qemu-system-aarch64: -drive file=root.img,format=raw,media=disk: PCI:
    Only PCI/PCIe bridges can be plugged into pxb-cxl

Jonathan explains this is due to on arm64 -drive is virtoi-blk by
default and we need to set a bus via the -device option. Do it as
Jonathan suggested in:

https://lore.kernel.org/linux-cxl/20250520183109.00002730@huawei.com/

From https://www.qemu.org/docs/master/system/qemu-manpage.html#hxtool-1

The QEMU block device handling options have a long history and have gone
through several iterations as the feature set and complexity of the
block layer have grown. Many online guides to QEMU often reference older
and deprecated options, which can lead to confusion.

The most explicit way to describe disks is to use a combination of
-device to specify the hardware device and -blockdev to describe the
backend. The device defines what the guest sees and the backend
describes how QEMU handles the data. It is the only guaranteed stable
interface for describing block devices and as such is recommended for
management tools and scripting.

The -drive option combines the device and backend into a single command
line option which is a more human friendly. There is however no
interface stability guarantee although some older board models still
need updating to work with the modern blockdev forms.

Co-developed-by: Jonathan Cameron Jonathan.Cameron@huawei.com
Co-developed-by: Itaru Kitayama itaru.kitayama@fujitsu.com
Tested-by: Itaru Kitayama itaru.kitayama@fujitsu.com
Signed-off-by: Marc Herbert marc.herbert@intel.com

[ikitayama]

@marc-hb thanks for this new PR. I've tested your proposed branch and I was able to get to the prompt (autologin) after commenting some Debian testing packages out from the list as the mkosi doesn't know how to expand the rootfs image as the number of packages grow.

I tested mkosi alone and tried to grow disk sizes, and with the recent mkosi, I think we need two .conf files:
10-root.conf and 20-esp.conf under the mkosi.repart directory.

[marc-hb]

@ikitayama I really don't understand how this PR can be related to Debian packages and disk sizes, is it? I mean, does this PR make any difference with respect to building the image? It really should not.

BTW every time I have a "disk full" message, -r wipe solves the problem for me. I don't really understand why but it does. Again: unrelated to this PR.

[ikitayama]

@marc-hb the wipe option -r wipe did not work in my set up that's why I reported here. It should not be a blocker to this PR.

[marc-hb]

the wipe option -r wipe did not work in my set up that's why I reported here.

You can also try rm -rf linux/qbuild/. Or, a different mkosi version?

[ikitayama]

I updated mkosi repository chcked out from GitHub and did not hit the mkosi image creation thanks.

At the top of the run_qemu.sh script:

[...]
shopt -s inherit_errexit

# default config
: "${builddir:=./qbuild}"
rootpw="root"
rootfssize="10G"
[...]

Is ths rootfssize shell variable honored during the execution? In my trial the image size of root.img.raw file is 2.4G.

[marc-hb]

Is ths rootfssize shell variable honored during the execution?

It depends:

• https://github.com/pmem/run_qemu/pull/212/files

[marc-hb]

I just realized QEMU silently ignores -snapshot now! Stay tuned...

      -snapshot
              Write to temporary files instead of disk image files. In this case, the raw disk image you use is not written back.
              You can however force the write back by pressing C-a s (see the Disk Images chapter in the System  Emulation  Users Guide).

              WARNING:
                 snapshot  is incompatible with -blockdev (instead use qemu-img to manually cre‐
                 ate snapshot images to attach to your blockdev).  If you have  mixed  -blockdev
                 and  -drive declarations you can use the 'snapshot' property on your drive dec‐
                 larations instead of this global option.

[marc-hb]

I just realized QEMU silently ignores -snapshot now! Stay tuned...

Tentative fix in #213