On 2021-07-06 15:05, Christoph Hellwig wrote:

On Tue, Jul 06, 2021 at 03:01:04PM +0100, Robin Murphy wrote:

quoted

FWIW I was pondering the question of whether to do something along those
lines or just scrap the default assignment entirely, so since I hadn't got
round to saying that I've gone ahead and hacked up the alternative
(similarly untested) for comparison :)

TBH I'm still not sure which one I prefer...

Claire did implement something like your suggestion originally, but
I don't really like it as it doesn't scale for adding multiple global
pools, e.g. for the 64-bit addressable one for the various encrypted
secure guest schemes.

Ah yes, that had slipped my mind, and it's a fair point indeed. Since 
we're not concerned with a minimal fix for backports anyway I'm more 
than happy to focus on Will's approach. Another thing is that that looks 
to take us a quiet step closer to the possibility of dynamically 
resizing a SWIOTLB pool, which is something that some of the hypervisor 
protection schemes looking to build on top of this series may want to 
explore at some point.

Robin.