On Mon, Sep 14, 2020 at 11:17:26AM -0300, Jason Gunthorpe wrote: > On Fri, Sep 11, 2020 at 09:42:25PM +0000, Clint Sbisa wrote: > > > There's no DMA involved with this BAR-- the driver writes a portion of the > > packet contents in addition to the descriptors, which generally increases the > > number of TLPs if write-combine isn't used. Furthermore, this BAR is only used > > for writes and never for reads. > > You use DPDK without DMA? How does receive work? That was not worded well. DMA is used, but the first X bytes of the packet are written directly to this BAR instead of being DMA'd-- the rest of the data is DMA'd. > > > As Jason noted in the other reply to this email, the Linux ENA driver makes use > > of WC by using devm_ioremap_wc(). > > As Ben noted we don't have kernel accessors to make this portable or > safe :( And therein lies our dilemma... Clint
