On Mon, Jan 14, 2019 at 03:49:07PM -0500, Konrad Rzeszutek Wilk wrote: > On Fri, Jan 11, 2019 at 10:12:31AM +0100, Joerg Roedel wrote: > > On Thu, Jan 10, 2019 at 12:02:05PM -0500, Konrad Rzeszutek Wilk wrote: > > > Why not use swiotlb_nr_tbl ? That is how drivers/gpu/drm use to figure if they > > > need to limit the size of pages. > > > > That function just exports the overall size of the swiotlb aperture, no? > > What I need here is the maximum size for a single mapping. > > Yes. The other drivers just assumed that if there is SWIOTLB they would use > the smaller size by default (as in they knew the limitation). > > But I agree it would be better to have something smarter - and also convert the > DRM drivers to piggy back on this. > > Or alternatively we could make SWIOTLB handle bigger sizes.. Just a thought: is it a good idea to teach blk_queue_max_segment_size to get the dma size? This will help us find other devices possibly missing this check. > > > > Regards, > > > > Joerg
