Quoting Daniel Vetter (2021-01-13 20:50:11) > On Wed, Jan 13, 2021 at 4:43 PM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > > > Quoting Daniel Vetter (2021-01-13 14:06:04) > > > We have too many people abusing the struct page they can get at but > > > really shouldn't in importers. Aside from that the backing page might > > > simply not exist (for dynamic p2p mappings) looking at it and using it > > > e.g. for mmap can also wreak the page handling of the exporter > > > completely. Importers really must go through the proper interface like > > > dma_buf_mmap for everything. > > > > If the exporter doesn't want to expose the struct page, why are they > > setting it in the exported sg_table? > > You need to store it somewhere, otherwise the dma-api doesn't work. > Essentially this achieves clearing/resetting the struct page pointer, > without additional allocations somewhere, or tons of driver changes > (since presumably the driver does keep track of the struct page > somewhere too). Only for mapping, and that's before the export -- if there's even a struct page to begin with. > Also as long as we have random importers looking at struct page we > can't just remove it, or crashes everywhere. So it has to be some > debug option you can disable. Totally agreed that nothing generic can rely on pages being transported via dma-buf, and memfd is there if you do want a suitable transport. The one I don't know about is dma-buf heap, do both parties there consent to transport pages via the dma-buf? i.e. do they have special cases for import/export between heaps? -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
