[PATCH v15 4/4] RDMA/mlx5: Support dma-buf based userspace memory region

From: Jianxin Xiong <jianxin.xiong@intel.com>
To: linux-rdma@vger.kernel.org, dri-devel@lists.freedesktop.org
Cc: Jianxin Xiong <jianxin.xiong@intel.com>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	Christian Koenig <christian.koenig@amd.com>,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: [PATCH v15 4/4] RDMA/mlx5: Support dma-buf based userspace memory region
Date: Thu, 10 Dec 2020 11:37:38 -0800	[thread overview]
Message-ID: <1607629058-141952-5-git-send-email-jianxin.xiong@intel.com> (raw)
In-Reply-To: <1607629058-141952-1-git-send-email-jianxin.xiong@intel.com>

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.

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>
---
 drivers/infiniband/hw/mlx5/main.c    |   2 +
 drivers/infiniband/hw/mlx5/mlx5_ib.h |  18 ++++++
 drivers/infiniband/hw/mlx5/mr.c      | 112 ++++++++++++++++++++++++++++++++++-
 drivers/infiniband/hw/mlx5/odp.c     |  89 ++++++++++++++++++++++++++--
 4 files changed, 214 insertions(+), 7 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 4a054eb..c025746 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
 /*
  * Copyright (c) 2013-2020, Mellanox Technologies inc. All rights reserved.
+ * Copyright (c) 2020, Intel Corporation. All rights reserved.
  */
 
 #include <linux/debugfs.h>
@@ -4069,6 +4070,7 @@ static int mlx5_ib_enable_driver(struct ib_device *dev)
 	.query_srq = mlx5_ib_query_srq,
 	.query_ucontext = mlx5_ib_query_ucontext,
 	.reg_user_mr = mlx5_ib_reg_user_mr,
+	.reg_user_mr_dmabuf = mlx5_ib_reg_user_mr_dmabuf,
 	.req_notify_cq = mlx5_ib_arm_cq,
 	.rereg_user_mr = mlx5_ib_rereg_user_mr,
 	.resize_cq = mlx5_ib_resize_cq,
diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index c33d6fd..bddf252 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
 /*
  * Copyright (c) 2013-2020, Mellanox Technologies inc. All rights reserved.
+ * Copyright (c) 2020, Intel Corporation. All rights reserved.
  */
 
 #ifndef MLX5_IB_H
@@ -703,6 +704,12 @@ static inline bool is_odp_mr(struct mlx5_ib_mr *mr)
 	       mr->umem->is_odp;
 }
 
+static inline bool is_dmabuf_mr(struct mlx5_ib_mr *mr)
+{
+	return IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING) && mr->umem &&
+	       mr->umem->is_dmabuf;
+}
+
 struct mlx5_ib_mw {
 	struct ib_mw		ibmw;
 	struct mlx5_core_mkey	mmkey;
@@ -1243,6 +1250,10 @@ int mlx5_ib_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 				  u64 virt_addr, int access_flags,
 				  struct ib_udata *udata);
+struct ib_mr *mlx5_ib_reg_user_mr_dmabuf(struct ib_pd *pd, u64 start,
+					 u64 length, u64 virt_addr,
+					 int fd, int access_flags,
+					 struct ib_udata *udata);
 int mlx5_ib_advise_mr(struct ib_pd *pd,
 		      enum ib_uverbs_advise_mr_advice advice,
 		      u32 flags,
@@ -1253,11 +1264,13 @@ int mlx5_ib_advise_mr(struct ib_pd *pd,
 int mlx5_ib_dealloc_mw(struct ib_mw *mw);
 int mlx5_ib_update_xlt(struct mlx5_ib_mr *mr, u64 idx, int npages,
 		       int page_shift, int flags);
+int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags);
 struct mlx5_ib_mr *mlx5_ib_alloc_implicit_mr(struct mlx5_ib_pd *pd,
 					     struct ib_udata *udata,
 					     int access_flags);
 void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *mr);
 void mlx5_ib_fence_odp_mr(struct mlx5_ib_mr *mr);
+void mlx5_ib_fence_dmabuf_mr(struct mlx5_ib_mr *mr);
 struct ib_mr *mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 				    u64 length, u64 virt_addr, int access_flags,
 				    struct ib_pd *pd, struct ib_udata *udata);
@@ -1345,6 +1358,7 @@ int mlx5_ib_advise_mr_prefetch(struct ib_pd *pd,
 			       enum ib_uverbs_advise_mr_advice advice,
 			       u32 flags, struct ib_sge *sg_list, u32 num_sge);
 int mlx5_ib_init_odp_mr(struct mlx5_ib_mr *mr);
+int mlx5_ib_init_dmabuf_mr(struct mlx5_ib_mr *mr);
 #else /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
 static inline void mlx5_ib_internal_fill_odp_caps(struct mlx5_ib_dev *dev)
 {
@@ -1370,6 +1384,10 @@ static inline int mlx5_ib_init_odp_mr(struct mlx5_ib_mr *mr)
 {
 	return -EOPNOTSUPP;
 }
+static inline int mlx5_ib_init_dmabuf_mr(struct mlx5_ib_mr *mr)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
 
 extern const struct mmu_interval_notifier_ops mlx5_mn_ops;
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 6fa869c..6b9c4dc 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>
@@ -934,6 +937,17 @@ 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)
@@ -943,7 +957,11 @@ 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(
@@ -979,7 +997,6 @@ 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;
@@ -1200,8 +1217,10 @@ 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;
@@ -1243,6 +1262,10 @@ 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++;
 	}
 
@@ -1566,6 +1589,84 @@ 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
@@ -1723,6 +1824,9 @@ struct ib_mr *mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 	if (flags & ~(IB_MR_REREG_TRANS | IB_MR_REREG_PD | IB_MR_REREG_ACCESS))
 		return ERR_PTR(-EOPNOTSUPP);
 
+	if (is_dmabuf_mr(mr))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	if (!(flags & IB_MR_REREG_ACCESS))
 		new_access_flags = mr->access_flags;
 	if (!(flags & IB_MR_REREG_PD))
@@ -1875,6 +1979,8 @@ 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);
 
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index aa2413b..440fbf7 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -33,6 +33,8 @@
 #include <rdma/ib_umem.h>
 #include <rdma/ib_umem_odp.h>
 #include <linux/kernel.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-resv.h>
 
 #include "mlx5_ib.h"
 #include "cmd.h"
@@ -670,6 +672,37 @@ void mlx5_ib_fence_odp_mr(struct mlx5_ib_mr *mr)
 	dma_fence_odp_mr(mr);
 }
 
+/**
+ * mlx5_ib_fence_dmabuf_mr - Stop all access to the dmabuf MR
+ * @mr: to fence
+ *
+ * On return no parallel threads will be touching this MR and no DMA will be
+ * active.
+ */
+void mlx5_ib_fence_dmabuf_mr(struct mlx5_ib_mr *mr)
+{
+	struct ib_umem_dmabuf *umem_dmabuf = to_ib_umem_dmabuf(mr->umem);
+
+	/* Prevent new page faults and prefetch requests from succeeding */
+	xa_erase(&mr_to_mdev(mr)->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
+
+	/* Wait for all running page-fault handlers to finish. */
+	synchronize_srcu(&mr_to_mdev(mr)->odp_srcu);
+
+	wait_event(mr->q_deferred_work, !atomic_read(&mr->num_deferred_work));
+
+	dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
+	mlx5_mr_cache_invalidate(mr);
+	umem_dmabuf->private = NULL;
+	ib_umem_dmabuf_unmap_pages(umem_dmabuf);
+	dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
+
+	if (!mr->cache_ent) {
+		mlx5_core_destroy_mkey(mr_to_mdev(mr)->mdev, &mr->mmkey);
+		WARN_ON(mr->descs);
+	}
+}
+
 #define MLX5_PF_FLAGS_DOWNGRADE BIT(1)
 #define MLX5_PF_FLAGS_SNAPSHOT BIT(2)
 #define MLX5_PF_FLAGS_ENABLE BIT(3)
@@ -803,6 +836,44 @@ static int pagefault_implicit_mr(struct mlx5_ib_mr *imr,
 	return ret;
 }
 
+static int pagefault_dmabuf_mr(struct mlx5_ib_mr *mr, size_t bcnt,
+			       u32 *bytes_mapped, u32 flags)
+{
+	struct ib_umem_dmabuf *umem_dmabuf = to_ib_umem_dmabuf(mr->umem);
+	u32 xlt_flags = 0;
+	int err;
+	unsigned int page_size;
+
+	if (flags & MLX5_PF_FLAGS_ENABLE)
+		xlt_flags |= MLX5_IB_UPD_XLT_ENABLE;
+
+	dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
+	err = ib_umem_dmabuf_map_pages(umem_dmabuf);
+	if (err) {
+		dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
+		return err;
+	}
+
+	page_size = mlx5_umem_find_best_pgsz(&umem_dmabuf->umem, mkc,
+					     log_page_size, 0,
+					     umem_dmabuf->umem.iova);
+	if (unlikely(page_size < PAGE_SIZE)) {
+		ib_umem_dmabuf_unmap_pages(umem_dmabuf);
+		err = -EINVAL;
+	} else {
+		err = mlx5_ib_update_mr_pas(mr, xlt_flags);
+	}
+	dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
+
+	if (err)
+		return err;
+
+	if (bytes_mapped)
+		*bytes_mapped += bcnt;
+
+	return ib_umem_num_pages(mr->umem);
+}
+
 /*
  * Returns:
  *  -EFAULT: The io_virt->bcnt is not within the MR, it covers pages that are
@@ -821,6 +892,9 @@ static int pagefault_mr(struct mlx5_ib_mr *mr, u64 io_virt, size_t bcnt,
 	if (unlikely(io_virt < mr->mmkey.iova))
 		return -EFAULT;
 
+	if (mr->umem->is_dmabuf)
+		return pagefault_dmabuf_mr(mr, bcnt, bytes_mapped, flags);
+
 	if (!odp->is_implicit_odp) {
 		u64 user_va;
 
@@ -847,6 +921,16 @@ int mlx5_ib_init_odp_mr(struct mlx5_ib_mr *mr)
 	return ret >= 0 ? 0 : ret;
 }
 
+int mlx5_ib_init_dmabuf_mr(struct mlx5_ib_mr *mr)
+{
+	int ret;
+
+	ret = pagefault_dmabuf_mr(mr, mr->umem->length, NULL,
+				  MLX5_PF_FLAGS_ENABLE);
+
+	return ret >= 0 ? 0 : ret;
+}
+
 struct pf_frame {
 	struct pf_frame *next;
 	u32 key;
@@ -1749,7 +1833,6 @@ static void destroy_prefetch_work(struct prefetch_mr_work *work)
 {
 	struct mlx5_ib_dev *dev = to_mdev(pd->device);
 	struct mlx5_core_mkey *mmkey;
-	struct ib_umem_odp *odp;
 	struct mlx5_ib_mr *mr;
 
 	lockdep_assert_held(&dev->odp_srcu);
@@ -1763,11 +1846,9 @@ static void destroy_prefetch_work(struct prefetch_mr_work *work)
 	if (mr->ibmr.pd != pd)
 		return NULL;
 
-	odp = to_ib_umem_odp(mr->umem);
-
 	/* prefetch with write-access must be supported by the MR */
 	if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE &&
-	    !odp->umem.writable)
+	    !mr->umem->writable)
 		return NULL;
 
 	return mr;
-- 
1.8.3.1

