We can write a simple "driver" like we did for Gluster
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@maxcuttins There are two packages. User level blktap driver that you referred blktap and a builtin kernel driver blktap2. Said patch is against mainline kernel as additional driver.
You still need to have user land blktap from https://github.com/xapi-project/blktap
There are instructions lying around https://xcp-ng.org/forum/topic/122/how-to-build-blktap-from-sources/ to build user land blktap (its without patch).