On Thu, Feb 28, 2019 at 11:42:24AM +0100, Stanislaw Gruszka wrote: > On Thu, Feb 28, 2019 at 10:04:12AM +0100, Stanislaw Gruszka wrote: > > On Tue, Feb 26, 2019 at 12:24:08PM +0100, Stanislaw Gruszka wrote: > > > On Tue, Feb 26, 2019 at 11:44:13AM +0100, Joerg Roedel wrote: > > > > On Tue, Feb 26, 2019 at 11:34:51AM +0100, Stanislaw Gruszka wrote: > > > > > On Tue, Feb 26, 2019 at 11:05:36AM +0100, Joerg Roedel wrote: > > > > > If sg->offset > PAGE_SIZE is fine then most likely we have problem with > > > > > alignment. > > > > > > > > The map_sg implementation in the AMD IOMMU driver uses sg_phys() which > > > > handles the sg->page + sg->offset calculation fine. > > > > > > > > > Note hat issue is with dma_map_sg(), switching to dma_map_single() > > > > > by using urb->transfer_buffer instead of urb->sg make things work > > > > > on AMD IOMMU. > > > > > > > > On the other hand this points to a bug in the driver, I'll look further > > > > if I can spot something there. > > > > > > I think so too. And I have done some changes that avoid strange allocation > > > scheme and use usb synchronous messages instead of allocating buffers > > > with unaligned sizes. However things work ok on Intel IOMMU and > > > there is no documentation what are dma_map_sg() requirement versus > > > dma_map_single() which works. I think there are some unwritten > > > requirements and things can work on some platforms and fails on others > > > (different IOMMUs, no-IOMMU on some ARCHes) > > > > For the record: we have another bug report with this issue: > > https://bugzilla.kernel.org/show_bug.cgi?id=202673 > > > > I provided there patch that change alignment for page_frag_alloc() and > > it did not fixed the problem. So this is not alignment issue. > > Now I think it could be page->refcount issue ... > > I looked at the map_sg() in amd_iommu.c code and one line looks suspicious > to me, seems we can use not correctly initialized s->dma_address (should be 0, > but I think can be non-zero if SG was reused). The code also seems do > not do correct thing if there is more than one SG with multiple pages > on individual segments. Something like in below patch seems to be more > appropriate to me (not tested nor compiled). Nevermind, the patch is wrong, s->dma_address is initalized in sg_num_pages(). Stanislaw
