RE: [PATCH v13 1/4] RDMA/umem: Support importing dma-buf as user memory region

-----Original Message----- From: Leon Romanovsky leon@kernel.org Sent: Monday, December 07, 2020 11:06 PM To: Xiong, Jianxin jianxin.xiong@intel.com Cc: linux-rdma@vger.kernel.org; dri-devel@lists.freedesktop.org; Doug Ledford dledford@redhat.com; Jason Gunthorpe jgg@ziepe.ca; Sumit Semwal sumit.semwal@linaro.org; Christian Koenig christian.koenig@amd.com; Vetter, Daniel daniel.vetter@intel.com Subject: Re: [PATCH v13 1/4] RDMA/umem: Support importing dma-buf as user memory region

On Mon, Dec 07, 2020 at 02:15:50PM -0800, Jianxin Xiong wrote:

...

Dma-buf is a standard cross-driver buffer sharing mechanism that can be used to support peer-to-peer access from RDMA devices.

Device memory exported via dma-buf is associated with a file descriptor. This is passed to the user space as a property associated with the buffer allocation. When the buffer is registered as a memory region, the file descriptor is passed to the RDMA driver along with other parameters.

Implement the common code for importing dma-buf object and mapping dma-buf pages.

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

Conflicts: include/rdma/ib_umem.h

This probably leftover from rebase, am I right?

Right. Should have removed it.

...

---

drivers/infiniband/core/Makefile | 2 +- drivers/infiniband/core/umem.c | 3 + drivers/infiniband/core/umem_dmabuf.c | 173 ++++++++++++++++++++++++++++++++++ include/rdma/ib_umem.h | 43 ++++++++- 4 files changed, 219 insertions(+), 2 deletions(-) create mode 100644 drivers/infiniband/core/umem_dmabuf.c

diff --git a/drivers/infiniband/core/Makefile b/drivers/infiniband/core/Makefile index ccf2670..8ab4eea 100644 --- a/drivers/infiniband/core/Makefile +++ b/drivers/infiniband/core/Makefile @@ -40,5 +40,5 @@ ib_uverbs-y := uverbs_main.o uverbs_cmd.o uverbs_marshall.o \ uverbs_std_types_srq.o \ uverbs_std_types_wq.o \ uverbs_std_types_qp.o -ib_uverbs-$(CONFIG_INFINIBAND_USER_MEM) += umem.o +ib_uverbs-$(CONFIG_INFINIBAND_USER_MEM) += umem.o umem_dmabuf.o ib_uverbs-$(CONFIG_INFINIBAND_ON_DEMAND_PAGING) += umem_odp.o diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index 7ca4112..cc131f8 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -2,6 +2,7 @@

• Copyright (c) 2005 Topspin Communications. All rights reserved.
• Copyright (c) 2005 Cisco Systems. All rights reserved.
• Copyright (c) 2005 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 @@ -278,6 +279,8 @@ void ib_umem_release(struct ib_umem *umem) { if (!umem) return;

• if (umem->is_dmabuf)

• return ib_umem_dmabuf_release(to_ib_umem_dmabuf(umem));
  

  if (umem->is_odp) return ib_umem_odp_release(to_ib_umem_odp(umem));

diff --git a/drivers/infiniband/core/umem_dmabuf.c b/drivers/infiniband/core/umem_dmabuf.c new file mode 100644 index 0000000..e50b955 --- /dev/null +++ b/drivers/infiniband/core/umem_dmabuf.c @@ -0,0 +1,173 @@ +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) +/*

• • Copyright (c) 2020 Intel Corporation. All rights reserved.
• */

+#include <linux/dma-buf.h> +#include <linux/dma-resv.h> +#include <linux/dma-mapping.h>

+#include "uverbs.h"

+int ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf *umem_dmabuf) {

• struct sg_table *sgt;
• struct scatterlist *sg;
• struct dma_fence *fence;
• unsigned long start, end, cur;
• unsigned int nmap;
• int i;
• dma_resv_assert_held(umem_dmabuf->attach->dmabuf->resv);
• if (umem_dmabuf->sgt)

• return 0;
  

• sgt = dma_buf_map_attachment(umem_dmabuf->attach, DMA_BIDIRECTIONAL);
• if (IS_ERR(sgt))

• return PTR_ERR(sgt);
  

• /* modify the sg list in-place to match umem address and length */
• start = ALIGN_DOWN(umem_dmabuf->umem.address, PAGE_SIZE);
• end = ALIGN(umem_dmabuf->umem.address + umem_dmabuf->umem.length,

•     PAGE_SIZE);
  

• cur = 0;
• nmap = 0;

Better to put as part of variable initialization.

...

• for_each_sgtable_dma_sg(sgt, sg, i) {

• if (start < cur + sg_dma_len(sg) && cur < end)
  

• 	nmap++;
  

• if (cur <= start && start < cur + sg_dma_len(sg)) {
  

• 	unsigned long offset = start - cur;
  

• 	umem_dmabuf->first_sg = sg;
  

• 	umem_dmabuf->first_sg_offset = offset;
  

• 	sg_dma_address(sg) += offset;
  

• 	sg_dma_len(sg) -= offset;
  

• 	cur += offset;
  

• }
  

• if (cur < end && end <= cur + sg_dma_len(sg)) {
  

• 	unsigned long trim = cur + sg_dma_len(sg) - end;
  

• 	umem_dmabuf->last_sg = sg;
  

• 	umem_dmabuf->last_sg_trim = trim;
  

• 	sg_dma_len(sg) -= trim;
  

• 	break;
  

• }
  

• cur += sg_dma_len(sg);
  

• }
• umem_dmabuf->umem.sg_head.sgl = umem_dmabuf->first_sg;
• umem_dmabuf->umem.sg_head.nents = nmap;
• umem_dmabuf->umem.nmap = nmap;
• umem_dmabuf->sgt = sgt;
• /*

• * Although the sg list is valid now, the content of the pages
  

• * may be not up-to-date. Wait for the exporter to finish
  

• * the migration.
  

• */
  

• fence = dma_resv_get_excl(umem_dmabuf->attach->dmabuf->resv);
• if (fence)

• dma_fence_wait(fence, false);
  

Any reason do not check return result from dma_fence_wait()?

...

• return 0;

+} +EXPORT_SYMBOL(ib_umem_dmabuf_map_pages);

+void ib_umem_dmabuf_unmap_pages(struct ib_umem_dmabuf *umem_dmabuf) {

• dma_resv_assert_held(umem_dmabuf->attach->dmabuf->resv);
• if (!umem_dmabuf->sgt)

• return;
  

• /* retore the original sg list */
• if (umem_dmabuf->first_sg) {

• sg_dma_address(umem_dmabuf->first_sg) -=
  

• 	umem_dmabuf->first_sg_offset;
  

• sg_dma_len(umem_dmabuf->first_sg) +=
  

• 	umem_dmabuf->first_sg_offset;
  

• umem_dmabuf->first_sg = NULL;
  

• umem_dmabuf->first_sg_offset = 0;
  

• }
• if (umem_dmabuf->last_sg) {

• sg_dma_len(umem_dmabuf->last_sg) +=
  

• 	umem_dmabuf->last_sg_trim;
  

• umem_dmabuf->last_sg = NULL;
  

• umem_dmabuf->last_sg_trim = 0;
  

• }
• dma_buf_unmap_attachment(umem_dmabuf->attach, umem_dmabuf->sgt,

• 		 DMA_BIDIRECTIONAL);
  

• umem_dmabuf->sgt = NULL;

+} +EXPORT_SYMBOL(ib_umem_dmabuf_unmap_pages);

+struct ib_umem *ib_umem_dmabuf_get(struct ib_device *device,

• 		   unsigned long offset, size_t size,
  

• 		   int fd, int access,
  

• 		   const struct dma_buf_attach_ops *ops) {
  

• struct dma_buf *dmabuf;
• struct ib_umem_dmabuf *umem_dmabuf;
• struct ib_umem *umem;
• unsigned long end;
• long ret = -EINVAL;

It is wrong type for the returned value. One of the possible options is to declare "struct ib_umem *ret;" and set ret = ERR_PTR(-EINVAL) or ret = ERR_CAST(dmabuf);

...

• if (check_add_overflow(offset, (unsigned long)size, &end))

• return ERR_PTR(-EINVAL);
  

• if (unlikely(!ops || !ops->move_notify))

Let's not put likely/unlikely in control paths.

...

• return ERR_PTR(-EINVAL);
  

• dmabuf = dma_buf_get(fd);
• if (IS_ERR(dmabuf))

• return (void *)dmabuf;
  

return ERR_CAST(dmabuf);

...

• if (dmabuf->size < end)

• goto out_release_dmabuf;
  

• umem_dmabuf = kzalloc(sizeof(*umem_dmabuf), GFP_KERNEL);
• if (!umem_dmabuf)

• return ERR_PTR(-ENOMEM);
  

You are leaking dmabuf here, forgot to call to dma_buf_put();

...

• umem = &umem_dmabuf->umem;
• umem->ibdev = device;
• umem->length = size;
• umem->address = offset;
• umem->writable = ib_access_writable(access);
• umem->is_dmabuf = 1;
• if (unlikely(!ib_umem_num_pages(umem)))

There is no advantage in "unlikely" here.

...

• goto out_free_umem;
  

• umem_dmabuf->attach = dma_buf_dynamic_attach(

• 			dmabuf,
  

• 			device->dma_device,
  

• 			ops,
  

• 			umem_dmabuf);
  

• if (IS_ERR(umem_dmabuf->attach)) {

• ret = PTR_ERR(umem_dmabuf->attach);
  

• goto out_free_umem;
  

• }
• return umem;

+out_free_umem:

• kfree(umem_dmabuf);

+out_release_dmabuf:

• dma_buf_put(dmabuf);
• return ERR_PTR(ret);

+} +EXPORT_SYMBOL(ib_umem_dmabuf_get);

+void ib_umem_dmabuf_release(struct ib_umem_dmabuf *umem_dmabuf) {

• struct dma_buf *dmabuf = umem_dmabuf->attach->dmabuf;
• dma_buf_detach(dmabuf, umem_dmabuf->attach);
• dma_buf_put(dmabuf);
• kfree(umem_dmabuf);

+} diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h index 7752211..b49a96d 100644 --- a/include/rdma/ib_umem.h +++ b/include/rdma/ib_umem.h @@ -1,6 +1,7 @@ /* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */ /*

• Copyright (c) 2007 Cisco Systems. All rights reserved.

• • Copyright (c) 2020 Intel Corporation. All rights reserved.
  */

#ifndef IB_UMEM_H @@ -13,6 +14,7 @@

struct ib_ucontext; struct ib_umem_odp; +struct dma_buf_attach_ops;

struct ib_umem { struct ib_device *ibdev; @@ -22,12 +24,29 @@ struct ib_umem { unsigned long address; u32 writable : 1; u32 is_odp : 1;

• u32 is_dmabuf : 1; struct work_struct work; struct sg_table sg_head; int nmap; unsigned int sg_nents;

};

+struct ib_umem_dmabuf {

• struct ib_umem umem;
• struct dma_buf_attachment *attach;
• struct sg_table *sgt;
• struct scatterlist *first_sg;
• struct scatterlist *last_sg;
• unsigned long first_sg_offset;
• unsigned long last_sg_trim;
• void *private;

+};

+static inline struct ib_umem_dmabuf *to_ib_umem_dmabuf(struct ib_umem +*umem) {

• return container_of(umem, struct ib_umem_dmabuf, umem); }

/* Returns the offset of the umem start relative to the first page. */ static inline int ib_umem_offset(struct ib_umem *umem) { @@ -86,6 +105,7 @@ int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset, unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem, unsigned long pgsz_bitmap, unsigned long virt);

/**

• ib_umem_find_best_pgoff - Find best HW page size

@@ -116,6 +136,14 @@ static inline unsigned long ib_umem_find_best_pgoff(struct ib_umem *umem, dma_addr & pgoff_bitmask); }

+struct ib_umem *ib_umem_dmabuf_get(struct ib_device *device,

• 		   unsigned long offset, size_t size,
  

• 		   int fd, int access,
  

• 		   const struct dma_buf_attach_ops *ops); int
  

+ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf *umem_dmabuf); void +ib_umem_dmabuf_unmap_pages(struct ib_umem_dmabuf *umem_dmabuf); void +ib_umem_dmabuf_release(struct ib_umem_dmabuf *umem_dmabuf);

#else /* CONFIG_INFINIBAND_USER_MEM */

#include <linux/err.h> @@ -143,7 +171,20 @@ static inline unsigned long ib_umem_find_best_pgoff(struct ib_umem *umem, { return 0; } +static inline struct ib_umem *ib_umem_dmabuf_get(struct ib_device *device,

• 				 unsigned long offset,
  

• 				 size_t size, int fd,
  

• 				 int access,
  

• 				 struct dma_buf_attach_ops *ops) {
  

• return ERR_PTR(-EINVAL);

Probably, It should be EOPNOTSUPP and not EINVAL.

...

+} +static inline int ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf +*umem_dmabuf) {

• return -EINVAL;

+} +static inline void ib_umem_dmabuf_unmap_pages(struct ib_umem_dmabuf +*umem_dmabuf) { } static inline void ib_umem_dmabuf_release(struct +ib_umem_dmabuf *umem_dmabuf) { }

#endif /* CONFIG_INFINIBAND_USER_MEM */

#endif /* IB_UMEM_H */

1.8.3.1