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dmabuf dma-addresses should not be dma_sync'd for CPU/device. Typically its the driver responsibility to dma_sync for CPU, but the driver should not dma_sync for CPU if the netmem is actually coming from a dmabuf memory provider. The page_pool already exposes a helper for dma_sync_for_cpu: page_pool_dma_sync_for_cpu. Upgrade this existing helper to handle netmem, and have it skip dma_sync if the memory is from a dmabuf memory provider. Drivers should migrate to using this helper when adding support for netmem. Also minimize the impact on the dma syncing performance for pages. Special case the dma-sync path for pages to not go through the overhead checks for dma-syncing and conversion to netmem. Cc: Alexander Lobakin <aleksander.lobakin@intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Signed-off-by: Mina Almasry <almasrymina@google.com> Link: https://patch.msgid.link/20241211212033.1684197-5-almasrymina@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>