added to release notes as per email:

<quote>
qcow and vmdk images are not supported. When manually configuring guests, the
image type for paravirtualized guests should be configured as tap:aio; for fully
virtualized guests, the image type should be file. Images backed by a physical
or logical device should use the phy type.
</quote>

making this bug block release notes, for tracking purposes.

"tap:aio;" should be "tap:aio:", and it would be clearer if file and phy were
referred to as "file:" or "phy:".

revised as follows:

<quote>
qcow and vmdk images are not supported. When manually configuring guests, the
image type for paravirtualized guests should be configured as tap:aio:. For
fully virtualized guests, the image type should be file:. Images backed by a
physical or logical device should use the phy: type.
</quote>

the final output should reflect a font difference with all the type names (can't
display here).

thanks!

On re-reading, it's still slightly ambiguous:

"When manually configuring guests, the
image type for paravirtualized guests should be configured as tap:aio:. For
fully virtualized guests, the image type should be file:."

all refers to file-backed domains only.  I suggest reordering:

qcow and vmdk images are not supported.  When manually configuring guests,
images backed by a physical or logical device should use the phy: type. 
File-backed images should use the tap:aio: image type for paravirtualized
guests, or file: for fully virtualized guests. 

Closing out.  Please ensure that a 5.1 bug is entered to track resolution of the
original issue.