Apologize for taking a long time - this got swamped in a sea of other
kernel bits.

There doesn't seem to be much of a point now to switch to the XArray
zero entry for what is currently DAX_ZERO_ENTRY. However, if you want
to explore it further, a potential thought could be adapting the bits
around the XArray 257 entry. There's a large swath of available bits
that we could use between bit 3 and bit 9. If Matthew really wants to
use the XA zero entry for it, perhaps we could shift the other DAX
bits to those?

Best regards,
Amy Parker
(she/her/hers)