On Mon, Jan 14, 2019 at 04:59:27PM -0500, Michael S. Tsirkin wrote: > 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. Yes, we should. Both the existing DMA size communicated through dma_params which is set by the driver, and this new DMA-ops exposed one which needs to be added. I'm working on some preliminary patches for the first part, as I think I introduced a bug related to that in the SCSI layer in 5.0..
