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Currently drivers get called to move a buffer, but if they have to move it temporarily through another space (SYSTEM->VRAM via TT) then they can end up with a lot of ttm->driver->ttm call stacks, if the temprorary space moves requires eviction. Instead of letting the driver do all the placement/space for the temporary, allow it to report back (-EMULTIHOP) and a placement (hop) to the move code, which will then do the temporary move, and the correct placement move afterwards. This removes a lot of code from drivers, at the expense of adding some midlayering. I've some further ideas on how to turn it inside out, but I think this is a good solution to the call stack problems. v2: separate out the driver patches, add WARN for getting MULTHOP in paths we shouldn't (Daniel) v3: use memset (Christian) Reviewed-by: Daniel Vetter <[email protected]> Reviewed-by: hristian König <[email protected]> Signed-off-by: Dave Airlie <[email protected]> Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]