Loading vmw_vsock_virtio_transport early at boot causes vsock to be
resident before any application opens an AF_VSOCK socket. Because the
kernel skips autoloading when the vsock module is already present,
vsock_loopback never gets loaded automatically, and any subsequent
bind() to VMADDR_CID_LOCAL fails with EADDRNOTAVAIL.
Fix this by explicitly loading vsock_loopback on virtio or VMWare
machines via the new may_have_vsock_looopback() helper, wich covers both
vmw_vsock_virtio_transport and vmware_vsock_vmci_transport case.
vsock_loopback is the only module that registers a transport for
VMADDR_CID_LOCAL (CID 1) and has no hard dependency from any of the
vsock transport modules.
Fixes: #41100
Follow-up for 381c78db491a7c5fad8697543dd36ebe9b848718
vlefebvre
7c1075fb8f