2021年9月8日(水) 16:20 Christoph Hellwig <hch@xxxxxxxxxxxxx>: > > On Wed, Sep 08, 2021 at 04:01:14PM +0900, Shunsuke Mie wrote: > > Thank you for your comment. > > > > > > On Wed, Sep 08, 2021 at 03:16:09PM +0900, Shunsuke Mie wrote: > > > > To share memory space using dma-buf, a API of the dma-buf requires dma > > > > device, but devices such as rxe do not have a dma device. For those case, > > > > change to specify a device of struct ib instead of the dma device. > > > > > > So if dma-buf doesn't actually need a device to dma map why do we ever > > > pass the dma_device here? Something does not add up. > > As described in the dma-buf api guide [1], the dma_device is used by dma-buf > > exporter to know the device buffer constraints of importer. > > [1] https://lwn.net/Articles/489703/ > > Which means for rxe you'd also have to pass the one for the underlying > net device. I thought of that way too. In that case, the memory region is constrained by the net device, but rxe driver copies data using CPU. To avoid the constraints, I decided to use the ib device. Thanks,
