On 11/16/2022 11:49 AM, Dean Luick wrote: > On 11/16/2022 9:45 AM, Christoph Hellwig wrote: >> On Wed, Nov 16, 2022 at 03:15:10PM +0000, Robin Murphy wrote: >>> Coherent DMA buffers are allocated by a kernel driver or subsystem for the >>> use of a device managed by that driver or subsystem, and thus they >>> fundamentally belong to the kernel as proxy for the device. Any coherent >>> DMA buffer may be mapped to userspace with the dma_mmap_*() interfaces, but >>> they're never a "userspace allocation" in that sense. >> >> Exactly. I could not find a place to map the buffers to userspace, >> so if it does that without using the proper interfaces we need to fix >> that as well. Dean, can you point me to the mmap code? > > See hfi1_file_mmap(), cases RCV_HDRQ and RCV_EGRBUF, for the two items you changed in hfi1. Both directly use remap_pfn_range(), which is probably the original approved call, but now is now buried deep within dma_mmap_*(). As you say - these should be updated. That said, the eager buffer mapping will stitch together multiple eager buffers into a single user map/vma. I don't see how to do that with the dma_mmap_*() interface. I have tested the proposed hfi1 changes. They are fine. Acked-by: Dean Luick <dean.luick@xxxxxxxxxxxxxxxxxxxx> Tested-by: Dean Luick <dean.luick@xxxxxxxxxxxxxxxxxxxx> Using dma_mmap_*() for the changed cases (e.g. rcvhdrq) fails. They are being looked at. I don't think they need to be part of this change. -Dean External recipient
