docs: improve qemu command line (#5540)

The suggested qemu command line in our local execution example
is rather old.

Change the discouraged -hd* options to the new
-device instead.

Further add a chance to use KVM acceleration to speed up the
example.

Finally we had several occasions to be working on x86 only.
We dropped arguments that can not work on cross-arch and
furthermore added a hint at how one could again native
performance on these platforms.

Fixes GH-5050

doc/rtd/howto/run_cloud_init_locally.rst

@@ -70,6 +70,12 @@ Download an Ubuntu image to run:
 
     wget https://cloud-images.ubuntu.com/jammy/current/jammy-server-cloudimg-amd64.img
 
+.. note::
+   This example uses emulated CPU instructions on non-x86 hosts, so it may be
+   slow. To make it faster on non-x86 architectures, one can change the image
+   type and :spelling:ignore:`qemu-system-<arch>` command name to match the
+   architecture of your host machine.
+
 Boot the image with the ISO attached
 ------------------------------------
 
@@ -78,8 +84,9 @@ Boot the cloud image with our configuration, :file:`seed.img`, to QEMU:
 .. code-block:: shell-session
 
     $ qemu-system-x86_64 -m 1024 -net nic -net user \
-        -hda jammy-server-cloudimg-amd64.img \
-        -hdb seed.img
+        -drive file=jammy-server-cloudimg-amd64.img,index=0,format=qcow2,media=disk \
+        -drive file=seed.img,index=1,media=cdrom \
+        -machine accel=kvm:tcg
 
 The now-booted image will allow for login using the password provided above.
 

doc/rtd/tutorial/qemu.rst

@@ -80,6 +80,12 @@ server image using :command:`wget`:
 
     $ wget https://cloud-images.ubuntu.com/jammy/current/jammy-server-cloudimg-amd64.img
 
+.. note::
+   This example uses emulated CPU instructions on non-x86 hosts, so it may be
+   slow. To make it faster on non-x86 architectures, one can change the image
+   type and :spelling:ignore:`qemu-system-<arch>` command name to match the
+   architecture of your host machine.
+
 Define our user data
 ====================
 
@@ -203,7 +209,6 @@ take a few moments to complete.
         -net nic                                                    \
         -net user                                                   \
         -machine accel=kvm:tcg                                      \
-        -cpu host                                                   \
         -m 512                                                      \
         -nographic                                                  \
         -hda jammy-server-cloudimg-amd64.img                        \

tools/.github-cla-signers

@@ -42,6 +42,7 @@ citrus-it
 cjp256
 CodeBleu
 Conan-Kudo
+cpaelzer
 cvstealth
 dankenigsberg
 dankm