Unable to use nested virtualization with LXC container

[Gio2241]

Required information

• Distribution: Ubuntu
• Distribution version: 22.04.2 LTS
• The output of "lxc info" or if that fails:
  • Kernel version: 5.15.0-71-generic
  • LXC version: 5.13
  • LXD version: 5.13
  • Storage backend in use: zfs | dir

Issue description

Unable to run LXD VM inside a LXD VM image (nested virtualization)

Steps to reproduce

on host:

lxc launch images:ubuntu/22.04 u22 -c security.nesting=true
lxc config device add u22 kvm unix-char source=/dev/kvm
lxc config device add u22 vhost-net unix-char source=/dev/vhost-net
lxc config device add u22 vhost-vsock unix-char source=/dev/vhost-vsock

lxc exec u22 bash

on VM:

...install snap and lxd

root@u22:~# kvm-ok
> INFO: /dev/kvm exists
> KVM acceleration can be used

lxc --version # 5.13
lxd init --auto

lxc launch images:ubuntu/22.04 u22 --vm

Getting this error:

Error: Failed instance creation: Failed creating instance record: Instance type "virtual-machine" is not supported on this server: Vsock support is missing (no /dev/vsock)

[tomponline]

Please show lxc config show <container> --expanded

[Gio2241]

If there is another LXC container running with a LXC VM inside, launch a VM inside a new LXC causes this error:

Error: Failed to run: forklimits fd=3 -- /snap/lxd/24846/bin/qemu-system-x86_64 -S -name u22 -uuid f09540b7-8133-425e-a68d-e69de6338a6e -daemonize -cpu host,hv_passthrough -nographic -serial chardev:console -nodefaults -no-user-config -sandbox on,obsolete=deny,elevateprivileges=allow,spawn=allow,resourcecontrol=deny -readconfig /var/snap/lxd/common/lxd/logs/u22/qemu.conf -spice unix=on,disable-ticketing=on,addr=/var/snap/lxd/common/lxd/logs/u22/qemu.spice -pidfile /var/snap/lxd/common/lxd/logs/u22/qemu.pid -D /var/snap/lxd/common/lxd/logs/u22/qemu.log -smbios type=2,manufacturer=Canonical Ltd.,product=LXD -runas lxd: : Process exited with non-zero value 1
Try `lxc info --show-log local:u22` for more info

--show log result:

Name: u22
Status: STOPPED
Type: virtual-machine
Architecture: x86_64
Created: 2023/05/17 11:09 UTC

Log:

qemu-system-x86_64:/var/snap/lxd/common/lxd/logs/u22/qemu.conf:115: vhost-vsock: unable to set guest cid: Address already in use

lxc config show u22 --expanded

architecture: x86_64
config:
  image.architecture: amd64
  image.description: Ubuntu jammy amd64 (20230517_07:42)
  image.os: Ubuntu
  image.release: jammy
  image.serial: "20230517_07:42"
  image.type: disk-kvm.img
  image.variant: default
  volatile.base_image: 2827820539fec451e353579dea6ee5a8fbead380e055c7e5700c019a751bdd76
  volatile.cloud-init.instance-id: 2b85d2a7-ec5e-4233-872d-4a3e7513a930
  volatile.eth0.hwaddr: 00:16:3e:05:de:19
  volatile.uuid: f09540b7-8133-425e-a68d-e69de6338a6e
  volatile.uuid.generation: f09540b7-8133-425e-a68d-e69de6338a6e
  volatile.vsock_id: "4"
devices:
  eth0:
    name: eth0
    network: lxdbr0
    type: nic
  root:
    path: /
    pool: default
    type: disk
ephemeral: false
profiles:
- default
stateful: false
description: ""

output for the another LXC VM:

architecture: x86_64
config:
  image.architecture: amd64
  image.description: Ubuntu jammy amd64 (20230517_07:42)
  image.os: Ubuntu
  image.release: jammy
  image.serial: "20230517_07:42"
  image.type: disk-kvm.img
  image.variant: default
  volatile.base_image: 2827820539fec451e353579dea6ee5a8fbead380e055c7e5700c019a751bdd76
  volatile.cloud-init.instance-id: 1b0874b0-4739-43d2-9dbe-f4ff99af6cd8
  volatile.eth0.host_name: tap628ed6fe
  volatile.eth0.hwaddr: 00:16:3e:03:fc:3e
  volatile.last_state.power: RUNNING
  volatile.uuid: b7783b4c-6b1d-4803-9f39-071c99841cc8
  volatile.uuid.generation: b7783b4c-6b1d-4803-9f39-071c99841cc8
  volatile.vsock_id: "4"
devices:
  eth0:
    name: eth0
    network: lxdbr0
    type: nic
  root:
    path: /
    pool: default
    type: disk
ephemeral: false
profiles:
- default
stateful: false
description: ""

I guess the reason is that both VMs within these LXC containers using same vsock_id volatile.vsock_id: "4"
The one gets first runs, the other failes

Race condition bug?

[tomponline]

Its a duplicate of https://github.com/lxc/lxd/issues/11508 in that case.