On Thu, Sep 17, 2020 at 12:25:02AM +0200, Robin Meinzer wrote:
Hi,
I have CCed Stefano Garzarella, who co-maintains virtio-vsock with me.
Please send technical questions to qemu-devel@nongnu.org in the future
and CC us. That way others can participate in the discussion and it's
archived in case someone else has the same question in the future.
> <div>- If I want to run multiple qemu instances with vsock in each of them, -device ... guest-cid=CID has to be different for every VM. I don't want to run VMs always manually, so can I assign a random or basically a free-to-take CID?<br/>
> This is what I would expect: -device ... guest-cid=ANY_CID<br/>
Userspace needs to allocate CIDs. The kernel does not automatically
allocate them. With Ethernet you would need to assign each guest a
unique MAC address, for example.
Is there some unique value associated with your guests that you can use?
> - I managed to send data from host to vm and vice versa via SOCK_STREAM. Although whenever I want to use SOCK_DGRAM, I get an error message with "no such device". Do you maybe know how to fix this to get a UDP-like connection?<br/>
virtio-vsock currently only supports SOCK_STREAM.
> - I see that from factory vsock is only read-write to root and noone else, so I have to run the VM as root. How does it look in practice, is it just for me or does any distro ship with /dev/vsock set to root only, because it feels like I shouldn't necessarily run a VM with root privileges.
A privileged process can open /dev/vhost-vsock and spawn an unprivileged
QEMU process with -device vhost-vsock-pci,guest-cid=CID,vhostfd=FD.
Stefan
--
I added Stefano Garzarella and qemu-devel as you asked. I wonder if you don't support SOCK_DGRAM but only SOCK_STREAM, why having code for it then? There are functions like vsock_dgram_connect and a proto_ops struct specifically for SOCK_DGRAM, but any attempt to create a socket for it ends with -ENODEV (transport_dgram is NULL, I guess it's on purpose because you don't support it as you said).
Another thing, could you please tell me what I have to set in the kernel .config to have vsockets working out of the box, for now lsmod doesn't show me vmw_vsock_transport_common or vsock or vsock_host existence in the form of a autoloaded module at all.
Greetings