On Thu, Nov 04, 2021 at 01:30:48AM -0700, Christoph Hellwig wrote:

Well, the whole problem is that we should not have to manage this at
all, and this is where I blame Intel.  There is no good reason to not
slightly overprovision the nvdimms and just do internal bad page
remapping like every other modern storage device.

What makes you think they don't?

The problem is persuading the CPU to do writes without doing reads.
That's where magic instructions or out of band IO is needed.