Cannot mount 9p fs between DomUs

[tristan.israel@xxxxxxxxxxx]

Hello,

I’m trying to setup a file sharing between two DomUs using the 9p protocol as 
described in https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html#Devices.

When I use the following configuration in the XL config file it works, but it 
shares a folder from the dom0: 
p9 = ['tag=test,security_model=none,path=/var’]

But when I want to connect to another DomU using the following config it does 
not work:
p9 = ['backend=p9-back,tag=test,security_model=none,path=/var’]

On the backend side I have no log…

On the frontend I have this in dmesg:
   xenbus_probe_frontend: Device with no driver: device/9pfs/0

then I modprobe 9pnet_xen and I have the following in dmesg:
        9pnet: Installing 9P2000 support
        Initialising Xen transport for 9pfs
        9pfs 9pfs-0: 2 xenbus_dev_probe on device/9pfs/0
        9pfs: probe of 9pfs-0 failed with error -2

Can anybody help me understand and fix this issue?

My understanding now is that there might be a problem with the transport 
between the DomUs, and probably on backend side but what exactly? Is there any 
module to load in the backend? A configuration? I think I read all Internet 
pages related to xen and P9FS.

Some info on my environment:
- Dom0 : Alpine Linux 3.15.4-lts in a VMware Fusion 12 virtual machine
- Xen 4.15.2
- DomU : Alpine Linux 3.15.4-virt

Thank you