RDMA/mlx5: Support dma-buf based userspace memory region

Implement the new driver method 'reg_user_mr_dmabuf'.  Utilize the core
functions to import dma-buf based memory region and update the mappings.

Add code to handle dma-buf related page fault.

Link: https://lore.kernel.org/r/1608067636-98073-5-git-send-email-jianxin.xiong@intel.com
Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Acked-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Acked-by: Christian Koenig <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 111 insertions, 8 deletions

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 24f8d59a42ea..a63ef7c66e38 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2013-2015, Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2020, Intel Corporation. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -36,6 +37,8 @@
 #include <linux/debugfs.h>
 #include <linux/export.h>
 #include <linux/delay.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-resv.h>
 #include <rdma/ib_umem.h>
 #include <rdma/ib_umem_odp.h>
 #include <rdma/ib_verbs.h>
@@ -935,6 +938,17 @@ static void set_mr_fields(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr,
 	mr->access_flags = access_flags;
 }
 
+static unsigned int mlx5_umem_dmabuf_default_pgsz(struct ib_umem *umem,
+						  u64 iova)
+{
+	/*
+	 * The alignment of iova has already been checked upon entering
+	 * UVERBS_METHOD_REG_DMABUF_MR
+	 */
+	umem->iova = iova;
+	return PAGE_SIZE;
+}
+
 static struct mlx5_ib_mr *alloc_cacheable_mr(struct ib_pd *pd,
 					     struct ib_umem *umem, u64 iova,
 					     int access_flags)
@@ -944,7 +958,11 @@ static struct mlx5_ib_mr *alloc_cacheable_mr(struct ib_pd *pd,
 	struct mlx5_ib_mr *mr;
 	unsigned int page_size;
 
-	page_size = mlx5_umem_find_best_pgsz(umem, mkc, log_page_size, 0, iova);
+	if (umem->is_dmabuf)
+		page_size = mlx5_umem_dmabuf_default_pgsz(umem, iova);
+	else
+		page_size = mlx5_umem_find_best_pgsz(umem, mkc, log_page_size,
+						     0, iova);
 	if (WARN_ON(!page_size))
 		return ERR_PTR(-EINVAL);
 	ent = mr_cache_ent_from_order(
@@ -980,7 +998,6 @@ static struct mlx5_ib_mr *alloc_cacheable_mr(struct ib_pd *pd,
 	mr->mmkey.size = umem->length;
 	mr->mmkey.pd = to_mpd(pd)->pdn;
 	mr->page_shift = order_base_2(page_size);
-	mr->umem = umem;
 	set_mr_fields(dev, mr, umem->length, access_flags);
 
 	return mr;
@@ -1201,8 +1218,10 @@ int mlx5_ib_update_xlt(struct mlx5_ib_mr *mr, u64 idx, int npages,
 
 /*
  * Send the DMA list to the HW for a normal MR using UMR.
+ * Dmabuf MR is handled in a similar way, except that the MLX5_IB_UPD_XLT_ZAP
+ * flag may be used.
  */
-static int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
+int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
 {
 	struct mlx5_ib_dev *dev = mr_to_mdev(mr);
 	struct device *ddev = &dev->mdev->pdev->dev;
@@ -1244,6 +1263,10 @@ static int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
 		cur_mtt->ptag =
 			cpu_to_be64(rdma_block_iter_dma_address(&biter) |
 				    MLX5_IB_MTT_PRESENT);
+
+		if (mr->umem->is_dmabuf && (flags & MLX5_IB_UPD_XLT_ZAP))
+			cur_mtt->ptag = 0;
+
 		cur_mtt++;
 	}
 
@@ -1567,6 +1590,84 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 	return create_real_mr(pd, umem, iova, access_flags);
 }
 
+static void mlx5_ib_dmabuf_invalidate_cb(struct dma_buf_attachment *attach)
+{
+	struct ib_umem_dmabuf *umem_dmabuf = attach->importer_priv;
+	struct mlx5_ib_mr *mr = umem_dmabuf->private;
+
+	dma_resv_assert_held(umem_dmabuf->attach->dmabuf->resv);
+
+	if (!umem_dmabuf->sgt)
+		return;
+
+	mlx5_ib_update_mr_pas(mr, MLX5_IB_UPD_XLT_ZAP);
+	ib_umem_dmabuf_unmap_pages(umem_dmabuf);
+}
+
+static struct dma_buf_attach_ops mlx5_ib_dmabuf_attach_ops = {
+	.allow_peer2peer = 1,
+	.move_notify = mlx5_ib_dmabuf_invalidate_cb,
+};
+
+struct ib_mr *mlx5_ib_reg_user_mr_dmabuf(struct ib_pd *pd, u64 offset,
+					 u64 length, u64 virt_addr,
+					 int fd, int access_flags,
+					 struct ib_udata *udata)
+{
+	struct mlx5_ib_dev *dev = to_mdev(pd->device);
+	struct mlx5_ib_mr *mr = NULL;
+	struct ib_umem_dmabuf *umem_dmabuf;
+	int err;
+
+	if (!IS_ENABLED(CONFIG_INFINIBAND_USER_MEM) ||
+	    !IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	mlx5_ib_dbg(dev,
+		    "offset 0x%llx, virt_addr 0x%llx, length 0x%llx, fd %d, access_flags 0x%x\n",
+		    offset, virt_addr, length, fd, access_flags);
+
+	/* dmabuf requires xlt update via umr to work. */
+	if (!mlx5_ib_can_load_pas_with_umr(dev, length))
+		return ERR_PTR(-EINVAL);
+
+	umem_dmabuf = ib_umem_dmabuf_get(&dev->ib_dev, offset, length, fd,
+					 access_flags,
+					 &mlx5_ib_dmabuf_attach_ops);
+	if (IS_ERR(umem_dmabuf)) {
+		mlx5_ib_dbg(dev, "umem_dmabuf get failed (%ld)\n",
+			    PTR_ERR(umem_dmabuf));
+		return ERR_CAST(umem_dmabuf);
+	}
+
+	mr = alloc_cacheable_mr(pd, &umem_dmabuf->umem, virt_addr,
+				access_flags);
+	if (IS_ERR(mr)) {
+		ib_umem_release(&umem_dmabuf->umem);
+		return ERR_CAST(mr);
+	}
+
+	mlx5_ib_dbg(dev, "mkey 0x%x\n", mr->mmkey.key);
+
+	atomic_add(ib_umem_num_pages(mr->umem), &dev->mdev->priv.reg_pages);
+	umem_dmabuf->private = mr;
+	init_waitqueue_head(&mr->q_deferred_work);
+	atomic_set(&mr->num_deferred_work, 0);
+	err = xa_err(xa_store(&dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key),
+			      &mr->mmkey, GFP_KERNEL));
+	if (err)
+		goto err_dereg_mr;
+
+	err = mlx5_ib_init_dmabuf_mr(mr);
+	if (err)
+		goto err_dereg_mr;
+	return &mr->ibmr;
+
+err_dereg_mr:
+	dereg_mr(dev, mr);
+	return ERR_PTR(err);
+}
+
 /**
  * mlx5_mr_cache_invalidate - Fence all DMA on the MR
  * @mr: The MR to fence
@@ -1740,8 +1841,8 @@ struct ib_mr *mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 				return ERR_PTR(err);
 			return NULL;
 		}
-		/* DM or ODP MR's don't have a umem so we can't re-use it */
-		if (!mr->umem || is_odp_mr(mr))
+		/* DM or ODP MR's don't have a normal umem so we can't re-use it */
+		if (!mr->umem || is_odp_mr(mr) || is_dmabuf_mr(mr))
 			goto recreate;
 
 		/*
@@ -1760,10 +1861,10 @@ struct ib_mr *mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 	}
 
 	/*
-	 * DM doesn't have a PAS list so we can't re-use it, odp does but the
-	 * logic around releasing the umem is different
+	 * DM doesn't have a PAS list so we can't re-use it, odp/dmabuf does
+	 * but the logic around releasing the umem is different
 	 */
-	if (!mr->umem || is_odp_mr(mr))
+	if (!mr->umem || is_odp_mr(mr) || is_dmabuf_mr(mr))
 		goto recreate;
 
 	if (!(new_access_flags & IB_ACCESS_ON_DEMAND) &&
@@ -1876,6 +1977,8 @@ static void dereg_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr)
 	/* Stop all DMA */
 	if (is_odp_mr(mr))
 		mlx5_ib_fence_odp_mr(mr);
+	else if (is_dmabuf_mr(mr))
+		mlx5_ib_fence_dmabuf_mr(mr);
 	else
 		clean_mr(dev, mr);