On Tue, Jun 04, 2019 at 02:45:32PM +0200, Andrey Konovalov wrote: > On Tue, Jun 4, 2019 at 2:27 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > On Tue, Jun 04, 2019 at 02:18:19PM +0200, Andrey Konovalov wrote: > > > On Mon, Jun 3, 2019 at 7:46 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > > > > > On Mon, Jun 03, 2019 at 06:55:14PM +0200, Andrey Konovalov wrote: > > > > > This patch is a part of a series that extends arm64 kernel ABI to allow to > > > > > pass tagged user pointers (with the top byte set to something else other > > > > > than 0x00) as syscall arguments. > > > > > > > > > > ib_uverbs_(re)reg_mr() use provided user pointers for vma lookups (through > > > > > e.g. mlx4_get_umem_mr()), which can only by done with untagged pointers. > > > > > > > > > > Untag user pointers in these functions. > > > > > > > > > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > > > > drivers/infiniband/core/uverbs_cmd.c | 4 ++++ > > > > > 1 file changed, 4 insertions(+) > > > > > > > > > > diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c > > > > > index 5a3a1780ceea..f88ee733e617 100644 > > > > > +++ b/drivers/infiniband/core/uverbs_cmd.c > > > > > @@ -709,6 +709,8 @@ static int ib_uverbs_reg_mr(struct uverbs_attr_bundle *attrs) > > > > > if (ret) > > > > > return ret; > > > > > > > > > > + cmd.start = untagged_addr(cmd.start); > > > > > + > > > > > if ((cmd.start & ~PAGE_MASK) != (cmd.hca_va & ~PAGE_MASK)) > > > > > return -EINVAL; > > > > > > > > I feel like we shouldn't thave to do this here, surely the cmd.start > > > > should flow unmodified to get_user_pages, and gup should untag it? > > > > > > > > ie, this sort of direction for the IB code (this would be a giant > > > > patch, so I didn't have time to write it all, but I think it is much > > > > saner): > > > > > > Hi Jason, > > > > > > ib_uverbs_reg_mr() passes cmd.start to mlx4_get_umem_mr(), which calls > > > find_vma(), which only accepts untagged addresses. Could you explain > > > how your patch helps? > > > > That mlx4 is just a 'weird duck', it is not the normal flow, and I > > don't think the core code should be making special consideration for > > it. > > How do you think we should do untagging (or something else) to deal > with this 'weird duck' case? mlx4 should handle it around the call to find_vma like other patches do, ideally as part of the cast from a void __user * to the unsigned long that find_vma needs Jason
