On Fri, Apr 27, 2018 at 11:36:23AM -0500, Christopher Lameter wrote: > On Fri, 27 Apr 2018, Matthew Wilcox wrote: > > > Some devices have incredibly bogus hardware like 28 bit addressing > > or 39 bit addressing. We don't have a good way to allocate memory by > > physical address other than than saying "GFP_DMA for anything less than > > 32, GFP_DMA32 (or GFP_KERNEL on 32-bit) for anything less than 64 bit". > > > > Even CMA doesn't have a "cma_alloc_phys()". Maybe that's the right place > > to put such an allocation API. > > The other way out of this would be to require a IOMMU? Which on many systems doesn't exist. And even if it exists might not be usable.
