On Wed, Jan 13, 2021 at 06:27:08PM +0000, Robin Murphy wrote:

quoted

Can we hook in somewhat lower level in the dma-direct code so that all
the remapping in dma-direct can be reused instead of duplicated?  That
also becomes important if we want to use non-remapping uncached support,
e.g. on mips or x86, or the direct changing of the attributes that Will
planned to look into for arm64.

Indeed, AFAICS this ought to boil down to a direct equivalent of 
__dma_direct_alloc_pages() - other than the address there should be no 
conceptual difference between pages from the restricted pool and those from 
the regular page allocator, so this probably deserves to be plumbed in as 
an alternative to that.

Yes, that's what I mean.  You managed to word it much better, though.