On Tue, Jun 10, 2025 at 07:06:39AM +0200, Christoph Hellwig wrote: > To get out of the DMA mapping helpers having to check every segment for > it's P2P status, ensure that bios either contain P2P transfers or non-P2P > transfers, and that a P2P bio only contains ranges from a single device. I may be out of the loop here. Is this an optimization to make something easier for the DMA layer? I don't think there's any fundamental reason why devices like nvme couldn't handle a command that uses memory mixed among multiple devices and/or host memory, at least. > This means we do the page zone access in the bio add path where it should > be still page hot, and will only have do the fairly expensive P2P topology > lookup once per bio down in the DMA mapping path, and only for already > marked bios.
