My intent here had not been to open up the entire SPI to review, but rather to get what I considered a rather nasty little corner case taken care of.

To me the simplest way to 'fix' to the current problem (without expanding the scope to put the whole SPI in question) is to have the implementation decouple region and access strategy as completely as is possible given the current constraints of the SPI, and then permit the implementations to recouple things together by way of failing when they cannot support a given configuration (e.g. various shared cache region/access strategy combinations). I'm going to try and code up something that comes close to this minimal fix against current master... and will report back.