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See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 96DFE80017 X-Stat-Signature: 1uhcpx83frzbik5u57b3d3useskhikcu X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1751028913-792854 X-HE-Meta: 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 C0pqo/Y7 5MjcJhgxuY2ijZ84nj0FHpTqK3fs+/WMR+QIBYjSk9liAxJcjq4UVUxiY4mZByUijLkvGTJ5Fyw/h1ioZAdEkFi2065kfljhjZiVrxNoqV69OiCsuMyZSVVUkrg2lQK6YeV6iXvpbK2B/yWOVMneGVjIbAerRvseU2ToBRw6NTTNrW9In7zH0twxr7bF61nGeBgcAZW2IYDff02AiEVj7RltBXzuleryuxwk8eC+jUJDT+8HZ3PeDljRkPJmqt6plNUKJ7VSMrNhHqhR7WzhrIHpM1iwTTh6+X1q/OppMpqTwbWwbEd9o97S2j+OO6bOm1dGkmkCMNswJ+iWCRYLZ+NletRZ1wznSJ7ybd1S1fHpwZtSfzHursb8tycLIzCjH0R+YCBzvnDxVNuBucnUfs9//FaR1g7zFLdpsQrjh7RKXV5s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 26, 2025 at 05:45:18PM +0100, Robin Murphy wrote: > Indeed that might actually end up pushing things in the opposite direction, > at least in some cases. Right now, a driver with, say, a 40-bit DMA mask is > usually better off not special-casing DMA buffers, and just making plain > GFP_KERNEL allocations for everything (on the assumption that 64-bit systems > with masses of memory *should* have SWIOTLB to cover things in the worst > case), vs. artificially constraining its DMA buffers to GFP_DMA32 and having > to deal with allocation failure more often. However with a more precise and > flexible allocator, there's then a much stronger incentive for such drivers > to explicitly mark *every* allocation that may be used for DMA, in order to > get the optimal behaviour. It really should be using dma_alloc_pages to ensure it gets addressable memory for these cases. For sub-page allocations it could use dmapool, but that's a little annoying because it does coherent allocations which 95% of the users don't actually need.