On Tue, Aug 27, 2019 at 03:53:29PM +0300, Gal Pressman wrote: > On 27/08/2019 15:00, Jason Gunthorpe wrote: > > On Tue, Aug 27, 2019 at 11:28:20AM +0300, Gal Pressman wrote: > >> On 26/08/2019 17:05, Gal Pressman wrote: > >>> Hi all, > >>> > >>> Lately I've been seeing DMA-API call traces on our automated testing runs which > >>> complain about overlapping mappings of the same cacheline [1]. > >>> The problem is (most likely) caused due to multiple calls to ibv_reg_mr with the > >>> same address, which as a result DMA maps the same physical addresses more than 7 > >>> (ACTIVE_CACHELINE_MAX_OVERLAP) times. > >> > >> BTW, on rare occasions I'm seeing the boundary check in check_sg_segment [1] > >> fail as well. I don't have a stable repro for it though. > >> > >> Is this a known issue as well? The comment there states it might be a bug in the > >> DMA API implementation, but I'm not sure. > >> > >> [1] https://elixir.bootlin.com/linux/v5.3-rc3/source/kernel/dma/debug.c#L1230 > > > > Maybe we are missing a dma_set_seg_boundary ? > > > > PCI uses low defaults: > > > > dma_set_max_seg_size(&dev->dev, 65536); > > dma_set_seg_boundary(&dev->dev, 0xffffffff); > > What would you set it to? Full 64 bits. For umem the driver is responsible to chop up the SGL as required, not the core code. Jason
