Linux Kernel Module Cheat

15.4.2. 9P getting started

As usual, we have already set everything up for you. On host:

cd "$(./getvar p9_dir)"
uname -a > host

Guest:

cd /mnt/9p/data
cat host
uname -a > guest

Host:

cat guest

The main ingredients for this are:

9P settings in our kernel configs
9p entry on our rootfs_overlay/etc/fstab

Alternatively, you could also mount your own with:
```
mkdir /mnt/my9p
mount -t 9p -o trans=virtio,version=9p2000.L host0 /mnt/my9p
```
where mount tag host0 is set by the emulator (mount_tag flag on QEMU CLI), and can be found in the guest with: cat /sys/bus/virtio/drivers/9pnet_virtio/virtio0/mount_tag as documented at: https://www.kernel.org/doc/Documentation/filesystems/9p.txt.
Launch QEMU with -virtfs as in your run script

When we tried:
```
security_model=mapped
```
writes from guest failed due to user mismatch problems: https://serverfault.com/questions/342801/read-write-access-for-passthrough-9p-filesystems-with-libvirt-qemu

Bibliography: