Blockfile snapshotter mounting requires a virtual machine means?

[markyangcc]

I noticed that blockfile snapshotter was recently added to containerd, and I realized that the documentation for blockfile has very little description, except for the following sentence,

• blockfile: A driver using raw block files for each snapshot. Block files are copied from a parent or base empty block file. Mounting requires a virtual machine or support for loopback mounts.

I understand loopback mount as mounting the blockfile to the host's directory via a loop device, what does it mean to mount using a virtual machine?

[markyangcc]

I think I got it now. Mounting requires a virtual machine mean mounting with kata-runtime(not runc, default), which backed by virtual machine