IB/mlx5: Allow creation of QPs with zero-length work queues

The current code attmepts to call ib_umem_get() even if the length is
zero, which causes a failure. Since the spec allows zero length work
queues, change the code so we don't call ib_umem_get() in those cases.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 29 insertions, 20 deletions

diff --git a/drivers/infiniband/hw/mlx5/qp.c b/drivers/infiniband/hw/mlx5/qp.c
index 87b7fb176f22..70dd77085db6 100644
--- a/drivers/infiniband/hw/mlx5/qp.c
+++ b/drivers/infiniband/hw/mlx5/qp.c
@@ -523,12 +523,12 @@ static int create_user_qp(struct mlx5_ib_dev *dev, struct ib_pd *pd,
 {
         struct mlx5_ib_ucontext *context;
         struct mlx5_ib_create_qp ucmd;
-        int page_shift;
+        int page_shift = 0;
         int uar_index;
         int npages;
-        u32 offset;
+        u32 offset = 0;
         int uuarn;
-        int ncont;
+        int ncont = 0;
         int err;
 
         err = ib_copy_from_udata(&ucmd, udata, sizeof(ucmd));
@@ -564,23 +564,29 @@ static int create_user_qp(struct mlx5_ib_dev *dev, struct ib_pd *pd,
         if (err)
                 goto err_uuar;
 
-        qp->umem = ib_umem_get(pd->uobject->context, ucmd.buf_addr,
-                               qp->buf_size, 0, 0);
-        if (IS_ERR(qp->umem)) {
-                mlx5_ib_dbg(dev, "umem_get failed\n");
-                err = PTR_ERR(qp->umem);
-                goto err_uuar;
+        if (ucmd.buf_addr && qp->buf_size) {
+                qp->umem = ib_umem_get(pd->uobject->context, ucmd.buf_addr,
+                                       qp->buf_size, 0, 0);
+                if (IS_ERR(qp->umem)) {
+                        mlx5_ib_dbg(dev, "umem_get failed\n");
+                        err = PTR_ERR(qp->umem);
+                        goto err_uuar;
+                }
+        } else {
+                qp->umem = NULL;
         }
 
-        mlx5_ib_cont_pages(qp->umem, ucmd.buf_addr, &npages, &page_shift,
-                           &ncont, NULL);
-        err = mlx5_ib_get_buf_offset(ucmd.buf_addr, page_shift, &offset);
-        if (err) {
-                mlx5_ib_warn(dev, "bad offset\n");
-                goto err_umem;
+        if (qp->umem) {
+                mlx5_ib_cont_pages(qp->umem, ucmd.buf_addr, &npages, &page_shift,
+                                   &ncont, NULL);
+                err = mlx5_ib_get_buf_offset(ucmd.buf_addr, page_shift, &offset);
+                if (err) {
+                        mlx5_ib_warn(dev, "bad offset\n");
+                        goto err_umem;
+                }
+                mlx5_ib_dbg(dev, "addr 0x%llx, size %d, npages %d, page_shift %d, ncont %d, offset %d\n",
+                            ucmd.buf_addr, qp->buf_size, npages, page_shift, ncont, offset);
         }
-        mlx5_ib_dbg(dev, "addr 0x%llx, size %d, npages %d, page_shift %d, ncont %d, offset %d\n",
-                    ucmd.buf_addr, qp->buf_size, npages, page_shift, ncont, offset);
 
         *inlen = sizeof(**in) + sizeof(*(*in)->pas) * ncont;
         *in = mlx5_vzalloc(*inlen);
@@ -588,7 +594,8 @@ static int create_user_qp(struct mlx5_ib_dev *dev, struct ib_pd *pd,
                 err = -ENOMEM;
                 goto err_umem;
         }
-        mlx5_ib_populate_pas(dev, qp->umem, page_shift, (*in)->pas, 0);
+        if (qp->umem)
+                mlx5_ib_populate_pas(dev, qp->umem, page_shift, (*in)->pas, 0);
         (*in)->ctx.log_pg_sz_remote_qpn =
                 cpu_to_be32((page_shift - MLX5_ADAPTER_PAGE_SHIFT) << 24);
         (*in)->ctx.params2 = cpu_to_be32(offset << 6);
@@ -619,7 +626,8 @@ err_free:
         mlx5_vfree(*in);
 
 err_umem:
-        ib_umem_release(qp->umem);
+        if (qp->umem)
+                ib_umem_release(qp->umem);
 
 err_uuar:
         free_uuar(&context->uuari, uuarn);
@@ -632,7 +640,8 @@ static void destroy_qp_user(struct ib_pd *pd, struct mlx5_ib_qp *qp)
 
         context = to_mucontext(pd->uobject->context);
         mlx5_ib_db_unmap_user(context, &qp->db);
-        ib_umem_release(qp->umem);
+        if (qp->umem)
+                ib_umem_release(qp->umem);
         free_uuar(&context->uuari, qp->uuarn);
 }