[Virtio-fs] Min host / vm kernel rev for basic DAX ops?

[Harry G. Coin]

Kindly answer a couple 'basic' virtiofs questions:

1) Which mainline kernel version is necessary for the host, and for the
vm to enable reliable DAX operations -- supposing no shared host
activity on the underlying fs.

2) Which host file system(s) have the best DAX performance while
offering xattr and related abilities?

Thanks