On Thu, Aug 23, 2018 at 10:01:45AM +1000, Benjamin Herrenschmidt wrote: > > The general scheme that architectures should implement is: > > > > ZONE_DMA: Any memory below a magic threshold that is lower than > > 32-bit. Only enabled if actually required (usually > > either 24-bit for ISA, or some other weird architecture > > specific value like 32-bit for S/390) > > It should have been ZONE_ISA_DMA :-)
For most of these use cases it should have been indeed, and that would avoid a lot of confusion where people use GFP_DMA just because they do DMA. Anyway, switching powerpc to this scheme would be great, but I don't think it is required - GFP_KERNEL will silently fall back to ZONE_DMA, so except for an additional GFP_DMA fallback allocation when the GFP_KERNEL one fails the code should just work.
