From: Jason Gunthorpe <jgg@xxxxxxxxxx>
The umem DMA list calculation was locked at 4k pages due to confusion
around how this API works and is used when larger pages are present.
The conclusion is:
- umem's cannot extend past what is mapped into the process, so creating
a lage page size and referring to a sub-range is not allowed
- umem's must always have a page offset of zero, except for sub PAGE_SIZE
umems
- The feature of umem_offset to create multiple objects inside a umem
is buggy and isn't used anyplace. Thus we can assume all users of the
current API have umem_offset == 0 as well
Provide a new page size calculator that limits the DMA list to the VA
range and enforces umem_offset == 0.
Allow user space to specify the page sizes which it can accept, this
bitmap must be derived from the intended use of the umem, based on
per-usage HW limitations.
Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
drivers/infiniband/hw/mlx5/devx.c | 64 ++++++++++++++++++++----
include/uapi/rdma/mlx5_user_ioctl_cmds.h | 1 +
2 files changed, 55 insertions(+), 10 deletions(-)
diff --git a/drivers/infiniband/hw/mlx5/devx.c b/drivers/infiniband/hw/mlx5/devx.c
index de3c2fc6f361..17ab369efc5e 100644
--- a/drivers/infiniband/hw/mlx5/devx.c
+++ b/drivers/infiniband/hw/mlx5/devx.c
@@ -2185,27 +2185,69 @@ static int devx_umem_get(struct mlx5_ib_dev *dev, struct ib_ucontext *ucontext,
return 0;
}
+static unsigned int devx_umem_find_best_pgsize(struct ib_umem *umem,
+ unsigned long pgsz_bitmap)
+{
+ unsigned long page_size;
+
+ /* Don't bother checking larger page sizes as offset must be zero and
+ * total DEVX umem length must be equal to total umem length.
+ */
+ pgsz_bitmap &= GENMASK_ULL(max_t(u64, order_base_2(umem->length),
+ PAGE_SHIFT),
+ MLX5_ADAPTER_PAGE_SHIFT);
+ if (!pgsz_bitmap)
+ return 0;
+
+ page_size = ib_umem_find_best_pgoff(umem, pgsz_bitmap, U64_MAX);
+ if (!page_size)
+ return 0;
+
+ /* If the page_size is less than the CPU page size then we can use the
+ * offset and create a umem which is a subset of the page list.
+ * For larger page sizes we can't be sure the DMA list reflects the
+ * VA so we must ensure that the umem extent is exactly equal to the
+ * page list. Reduce the page size until one of these cases is true.
+ */
+ while ((ib_umem_dma_offset(umem, page_size) != 0 ||
+ (umem->length % page_size) != 0) &&
+ page_size > PAGE_SIZE)
+ page_size /= 2;
+
+ return page_size;
+}
+
static int devx_umem_reg_cmd_alloc(struct mlx5_ib_dev *dev,
struct uverbs_attr_bundle *attrs,
struct devx_umem *obj,
struct devx_umem_reg_cmd *cmd)
{
+ unsigned long pgsz_bitmap;
unsigned int page_size;
__be64 *mtt;
void *umem;
+ int ret;
/*
- * We don't know what the user intends to use this umem for, but the HW
- * restrictions must be met. MR, doorbell records, QP, WQ and CQ all
- * have different requirements. Since we have no idea how to sort this
- * out, only support PAGE_SIZE with the expectation that userspace will
- * provide the necessary alignments inside the known PAGE_SIZE and that
- * FW will check everything.
+ * If the user does not pass in pgsz_bitmap then the user promises not
+ * to use umem_offset!=0 in any commands that allocate on top of the
+ * umem.
+ *
+ * If the user wants to use a umem_offset then it must pass in
+ * pgsz_bitmap which guides the maximum page size and thus maximum
+ * object alignment inside the umem. See the PRM.
+ *
+ * Users are not allowed to use IOVA here, mkeys are not supported on
+ * umem.
*/
- page_size = ib_umem_find_best_pgoff(
- obj->umem, PAGE_SIZE,
- __mlx5_page_offset_to_bitmask(__mlx5_bit_sz(umem, page_offset),
- 0));
+ ret = uverbs_get_const_default(&pgsz_bitmap, attrs,
+ MLX5_IB_ATTR_DEVX_UMEM_REG_PGSZ_BITMAP,
+ GENMASK_ULL(63,
+ min(PAGE_SHIFT, MLX5_ADAPTER_PAGE_SHIFT)));
+ if (ret)
+ return ret;
+
+ page_size = devx_umem_find_best_pgsize(obj->umem, pgsz_bitmap);
if (!page_size)
return -EINVAL;
@@ -2791,6 +2833,8 @@ DECLARE_UVERBS_NAMED_METHOD(
UA_MANDATORY),
UVERBS_ATTR_FLAGS_IN(MLX5_IB_ATTR_DEVX_UMEM_REG_ACCESS,
enum ib_access_flags),
+ UVERBS_ATTR_CONST_IN(MLX5_IB_ATTR_DEVX_UMEM_REG_PGSZ_BITMAP,
+ u64),
UVERBS_ATTR_PTR_OUT(MLX5_IB_ATTR_DEVX_UMEM_REG_OUT_ID,
UVERBS_ATTR_TYPE(u32),
UA_MANDATORY));
diff --git a/include/uapi/rdma/mlx5_user_ioctl_cmds.h b/include/uapi/rdma/mlx5_user_ioctl_cmds.h
index 3fd9b380a091..3f0bc7597ba7 100644
--- a/include/uapi/rdma/mlx5_user_ioctl_cmds.h
+++ b/include/uapi/rdma/mlx5_user_ioctl_cmds.h
@@ -154,6 +154,7 @@ enum mlx5_ib_devx_umem_reg_attrs {
MLX5_IB_ATTR_DEVX_UMEM_REG_LEN,
MLX5_IB_ATTR_DEVX_UMEM_REG_ACCESS,
MLX5_IB_ATTR_DEVX_UMEM_REG_OUT_ID,
+ MLX5_IB_ATTR_DEVX_UMEM_REG_PGSZ_BITMAP,
};
enum mlx5_ib_devx_umem_dereg_attrs {
--
2.29.2
