[Qemu-devel] How to access to ivshmem device in VM ?

[Sébastien Frémal]

Hello !

I searched for a forum or a place where questions about QEMU can be asked,
but I found nothing except mailing lists. If there is a more appropriate
place for my question, do not hesitate to indicate it to me !!

So, I'm trying to use ivshmem to share memory pages between several VM. I
found many webpages documenting the set up of this device. I successfully
installed the mechanism in the host. I launched ivshmem-clients which
successfully connected to the server. The problem is that I can't
understand how to access to the shared memory pages in a VM. I launched my
VM with this command line :
sudo qemu-system-x86_64 -show-cursor -enable-kvm -drive
format=raw,file=/var/lib/libvirt/images/theRise.img -m 4096 -machine q35
-show-cursor -device ivshmem-doorbell,vectors=4,chardev=ivshmem -chardev
socket,path=/tmp/ivshmem_socket,id=ivshmem
(the server was launched with : sudo ivshmem-server -p
/var/run/ivshmem-server.pid -S /tmp/ivshmem_socket -M ivshmem -l 4K -n 4).

The VM executes properly (I just don't have a visible mouse cursor despite
the "-show-cursor" option, but it could be worse) but I have absolutely no
idea on how to access the ivshmem device. I firstly thought that the option
would add a new device in /dev but there is nothing special. I ran an
updatedb/locate ivshmem to check if there was something interesting on the
machine, but there is no results. I don't know which socket path I must
give to my ivshmem client in my VM so it can connect to my server. I
searched for this particular information on the web, but I found nothing.

Can someone indicate me how to connect to the ivshmem-server from a VM
please ?

Best regards,

Sebastien Fremal