From: Yishai Hadas yishaih@nvidia.com

Expose DMABUF functionality to userspace through the uverbs interface, enabling InfiniBand/RDMA devices to export PCI based memory regions (e.g. device memory) as DMABUF file descriptors. This allows zero-copy sharing of RDMA memory with other subsystems that support the dma-buf framework.

A new UVERBS_OBJECT_DMABUF object type and allocation method were introduced.

During allocation, uverbs invokes the driver to supply the rdma_user_mmap_entry associated with the given page offset (pgoff).

Based on the returned rdma_user_mmap_entry, uverbs requests the driver to provide the corresponding physical-memory details as well as the driver’s PCI provider information.

Using this information, dma_buf_export() is called; if it succeeds, uobj->object is set to the underlying file pointer returned by the dma-buf framework.

The file descriptor number follows the standard uverbs allocation flow, but the file pointer comes from the dma-buf subsystem, including its own fops and private data.

Because of this, alloc_begin_fd_uobject() must handle cases where fd_type->fops is NULL, and both alloc_commit_fd_uobject() and alloc_abort_fd_uobject() must account for whether filp->private_data exists, since it is only populated after a successful dma_buf_export().

When an mmap entry is removed, uverbs iterates over its associated DMABUFs, marks them as revoked, and calls dma_buf_move_notify() so that their importers are notified.

The same procedure applies during the disassociate flow; final cleanup occurs when the application closes the file.

Signed-off-by: Yishai Hadas yishaih@nvidia.com Signed-off-by: Edward Srouji edwards@nvidia.com --- drivers/infiniband/core/Makefile | 1 + drivers/infiniband/core/device.c | 2 + drivers/infiniband/core/ib_core_uverbs.c | 19 +++ drivers/infiniband/core/rdma_core.c | 63 ++++---- drivers/infiniband/core/rdma_core.h | 1 + drivers/infiniband/core/uverbs.h | 10 ++ drivers/infiniband/core/uverbs_std_types_dmabuf.c | 172 ++++++++++++++++++++++ drivers/infiniband/core/uverbs_uapi.c | 1 + include/rdma/ib_verbs.h | 9 ++ include/rdma/uverbs_types.h | 1 + include/uapi/rdma/ib_user_ioctl_cmds.h | 10 ++ 11 files changed, 263 insertions(+), 26 deletions(-)

diff --git a/drivers/infiniband/core/Makefile b/drivers/infiniband/core/Makefile index f483e0c12444..a2a7a9d2e0d3 100644 --- a/drivers/infiniband/core/Makefile +++ b/drivers/infiniband/core/Makefile @@ -33,6 +33,7 @@ ib_umad-y := user_mad.o ib_uverbs-y := uverbs_main.o uverbs_cmd.o uverbs_marshall.o \ rdma_core.o uverbs_std_types.o uverbs_ioctl.o \ uverbs_std_types_cq.o \ + uverbs_std_types_dmabuf.o \ uverbs_std_types_dmah.o \ uverbs_std_types_flow_action.o uverbs_std_types_dm.o \ uverbs_std_types_mr.o uverbs_std_types_counters.o \ diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c index 4e09f6e0995e..416242b9c158 100644 --- a/drivers/infiniband/core/device.c +++ b/drivers/infiniband/core/device.c @@ -2765,6 +2765,7 @@ void ib_set_device_ops(struct ib_device *dev, const struct ib_device_ops *ops) SET_DEVICE_OP(dev_ops, map_mr_sg); SET_DEVICE_OP(dev_ops, map_mr_sg_pi); SET_DEVICE_OP(dev_ops, mmap); + SET_DEVICE_OP(dev_ops, mmap_get_pfns); SET_DEVICE_OP(dev_ops, mmap_free); SET_DEVICE_OP(dev_ops, modify_ah); SET_DEVICE_OP(dev_ops, modify_cq); @@ -2775,6 +2776,7 @@ void ib_set_device_ops(struct ib_device *dev, const struct ib_device_ops *ops) SET_DEVICE_OP(dev_ops, modify_srq); SET_DEVICE_OP(dev_ops, modify_wq); SET_DEVICE_OP(dev_ops, peek_cq); + SET_DEVICE_OP(dev_ops, pgoff_to_mmap_entry); SET_DEVICE_OP(dev_ops, pre_destroy_cq); SET_DEVICE_OP(dev_ops, poll_cq); SET_DEVICE_OP(dev_ops, port_groups); diff --git a/drivers/infiniband/core/ib_core_uverbs.c b/drivers/infiniband/core/ib_core_uverbs.c index b51bd7087a88..1ff53b8a0e89 100644 --- a/drivers/infiniband/core/ib_core_uverbs.c +++ b/drivers/infiniband/core/ib_core_uverbs.c @@ -5,9 +5,13 @@ * Copyright 2019 Marvell. All rights reserved. */ #include <linux/xarray.h> +#include <linux/dma-buf.h> +#include <linux/dma-resv.h> #include "uverbs.h" #include "core_priv.h"

+MODULE_IMPORT_NS("DMA_BUF"); + /** * rdma_umap_priv_init() - Initialize the private data of a vma * @@ -229,12 +233,24 @@ EXPORT_SYMBOL(rdma_user_mmap_entry_put); */ void rdma_user_mmap_entry_remove(struct rdma_user_mmap_entry *entry) { + struct ib_uverbs_dmabuf_file *uverbs_dmabuf, *tmp; + if (!entry) return;

+ mutex_lock(&entry->dmabufs_lock); xa_lock(&entry->ucontext->mmap_xa); entry->driver_removed = true; xa_unlock(&entry->ucontext->mmap_xa); + list_for_each_entry_safe(uverbs_dmabuf, tmp, &entry->dmabufs, dmabufs_elm) { + dma_resv_lock(uverbs_dmabuf->dmabuf->resv, NULL); + list_del(&uverbs_dmabuf->dmabufs_elm); + uverbs_dmabuf->revoked = true; + dma_buf_move_notify(uverbs_dmabuf->dmabuf); + dma_resv_unlock(uverbs_dmabuf->dmabuf->resv); + } + mutex_unlock(&entry->dmabufs_lock); + kref_put(&entry->ref, rdma_user_mmap_entry_free); } EXPORT_SYMBOL(rdma_user_mmap_entry_remove); @@ -274,6 +290,9 @@ int rdma_user_mmap_entry_insert_range(struct ib_ucontext *ucontext, return -EINVAL;

kref_init(&entry->ref); + INIT_LIST_HEAD(&entry->dmabufs); + mutex_init(&entry->dmabufs_lock); + entry->ucontext = ucontext;

/* diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c index 18918f463361..3e0a8b9cd288 100644 --- a/drivers/infiniband/core/rdma_core.c +++ b/drivers/infiniband/core/rdma_core.c @@ -465,7 +465,7 @@ alloc_begin_fd_uobject(const struct uverbs_api_object *obj,

fd_type = container_of(obj->type_attrs, struct uverbs_obj_fd_type, type); - if (WARN_ON(fd_type->fops->release != &uverbs_uobject_fd_release && + if (WARN_ON(fd_type->fops && fd_type->fops->release != &uverbs_uobject_fd_release && fd_type->fops->release != &uverbs_async_event_release)) { ret = ERR_PTR(-EINVAL); goto err_fd; @@ -477,14 +477,16 @@ alloc_begin_fd_uobject(const struct uverbs_api_object *obj, goto err_fd; }

- /* Note that uverbs_uobject_fd_release() is called during abort */ - filp = anon_inode_getfile(fd_type->name, fd_type->fops, NULL, - fd_type->flags); - if (IS_ERR(filp)) { - ret = ERR_CAST(filp); - goto err_getfile; + if (fd_type->fops) { + /* Note that uverbs_uobject_fd_release() is called during abort */ + filp = anon_inode_getfile(fd_type->name, fd_type->fops, NULL, + fd_type->flags); + if (IS_ERR(filp)) { + ret = ERR_CAST(filp); + goto err_getfile; + } + uobj->object = filp; } - uobj->object = filp;

uobj->id = new_fd; return uobj; @@ -561,7 +563,9 @@ static void alloc_abort_fd_uobject(struct ib_uobject *uobj) { struct file *filp = uobj->object;

- fput(filp); + if (filp) + fput(filp); + put_unused_fd(uobj->id); }

@@ -628,11 +632,14 @@ static void alloc_commit_fd_uobject(struct ib_uobject *uobj) /* This shouldn't be used anymore. Use the file object instead */ uobj->id = 0;

- /* - * NOTE: Once we install the file we loose ownership of our kref on - * uobj. It will be put by uverbs_uobject_fd_release() - */ - filp->private_data = uobj; + if (!filp->private_data) { + /* + * NOTE: Once we install the file we loose ownership of our kref on + * uobj. It will be put by uverbs_uobject_fd_release() + */ + filp->private_data = uobj; + } + fd_install(fd, filp); }

@@ -802,21 +809,10 @@ const struct uverbs_obj_type_class uverbs_idr_class = { }; EXPORT_SYMBOL(uverbs_idr_class);

-/* - * Users of UVERBS_TYPE_ALLOC_FD should set this function as the struct - * file_operations release method. - */ -int uverbs_uobject_fd_release(struct inode *inode, struct file *filp) +int uverbs_uobject_release(struct ib_uobject *uobj) { struct ib_uverbs_file *ufile; - struct ib_uobject *uobj;

- /* - * This can only happen if the fput came from alloc_abort_fd_uobject() - */ - if (!filp->private_data) - return 0; - uobj = filp->private_data; ufile = uobj->ufile;

if (down_read_trylock(&ufile->hw_destroy_rwsem)) { @@ -843,6 +839,21 @@ int uverbs_uobject_fd_release(struct inode *inode, struct file *filp) uverbs_uobject_put(uobj); return 0; } + +/* + * Users of UVERBS_TYPE_ALLOC_FD should set this function as the struct + * file_operations release method. + */ +int uverbs_uobject_fd_release(struct inode *inode, struct file *filp) +{ + /* + * This can only happen if the fput came from alloc_abort_fd_uobject() + */ + if (!filp->private_data) + return 0; + + return uverbs_uobject_release(filp->private_data); +} EXPORT_SYMBOL(uverbs_uobject_fd_release);

/* diff --git a/drivers/infiniband/core/rdma_core.h b/drivers/infiniband/core/rdma_core.h index a59b087611cb..55f1e3558856 100644 --- a/drivers/infiniband/core/rdma_core.h +++ b/drivers/infiniband/core/rdma_core.h @@ -156,6 +156,7 @@ extern const struct uapi_definition uverbs_def_obj_counters[]; extern const struct uapi_definition uverbs_def_obj_cq[]; extern const struct uapi_definition uverbs_def_obj_device[]; extern const struct uapi_definition uverbs_def_obj_dm[]; +extern const struct uapi_definition uverbs_def_obj_dmabuf[]; extern const struct uapi_definition uverbs_def_obj_dmah[]; extern const struct uapi_definition uverbs_def_obj_flow_action[]; extern const struct uapi_definition uverbs_def_obj_intf[]; diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h index 797e2fcc8072..66287e8e7ad7 100644 --- a/drivers/infiniband/core/uverbs.h +++ b/drivers/infiniband/core/uverbs.h @@ -133,6 +133,16 @@ struct ib_uverbs_completion_event_file { struct ib_uverbs_event_queue ev_queue; };

+struct ib_uverbs_dmabuf_file { + struct ib_uobject uobj; + struct dma_buf *dmabuf; + struct list_head dmabufs_elm; + struct rdma_user_mmap_entry *mmap_entry; + struct dma_buf_phys_vec phys_vec; + struct p2pdma_provider *provider; + u8 revoked :1; +}; + struct ib_uverbs_event { union { struct ib_uverbs_async_event_desc async; diff --git a/drivers/infiniband/core/uverbs_std_types_dmabuf.c b/drivers/infiniband/core/uverbs_std_types_dmabuf.c new file mode 100644 index 000000000000..ef5484022e77 --- /dev/null +++ b/drivers/infiniband/core/uverbs_std_types_dmabuf.c @@ -0,0 +1,172 @@ +// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB +/* + * Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved + */ + +#include <linux/dma-buf-mapping.h> +#include <linux/pci-p2pdma.h> +#include <linux/dma-resv.h> +#include <rdma/uverbs_std_types.h> +#include "rdma_core.h" +#include "uverbs.h" + +static int uverbs_dmabuf_attach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attachment) +{ + struct ib_uverbs_dmabuf_file *priv = dmabuf->priv; + + if (!attachment->peer2peer) + return -EOPNOTSUPP; + + if (priv->revoked) + return -ENODEV; + + return 0; +} + +static struct sg_table * +uverbs_dmabuf_map(struct dma_buf_attachment *attachment, + enum dma_data_direction dir) +{ + struct ib_uverbs_dmabuf_file *priv = attachment->dmabuf->priv; + + dma_resv_assert_held(priv->dmabuf->resv); + + if (priv->revoked) + return ERR_PTR(-ENODEV); + + return dma_buf_phys_vec_to_sgt(attachment, priv->provider, + &priv->phys_vec, 1, priv->phys_vec.len, + dir); +} + +static void uverbs_dmabuf_unmap(struct dma_buf_attachment *attachment, + struct sg_table *sgt, + enum dma_data_direction dir) +{ + dma_buf_free_sgt(attachment, sgt, dir); +} + +static void uverbs_dmabuf_release(struct dma_buf *dmabuf) +{ + struct ib_uverbs_dmabuf_file *priv = dmabuf->priv; + + /* + * This can only happen if the fput came from alloc_abort_fd_uobject() + */ + if (!priv->uobj.context) + return; + + uverbs_uobject_release(&priv->uobj); +} + +static const struct dma_buf_ops uverbs_dmabuf_ops = { + .attach = uverbs_dmabuf_attach, + .map_dma_buf = uverbs_dmabuf_map, + .unmap_dma_buf = uverbs_dmabuf_unmap, + .release = uverbs_dmabuf_release, +}; + +static int UVERBS_HANDLER(UVERBS_METHOD_DMABUF_ALLOC)( + struct uverbs_attr_bundle *attrs) +{ + struct ib_uobject *uobj = + uverbs_attr_get(attrs, UVERBS_ATTR_ALLOC_DMABUF_HANDLE) + ->obj_attr.uobject; + struct ib_uverbs_dmabuf_file *uverbs_dmabuf = + container_of(uobj, struct ib_uverbs_dmabuf_file, uobj); + struct ib_device *ib_dev = attrs->context->device; + struct rdma_user_mmap_entry *mmap_entry; + DEFINE_DMA_BUF_EXPORT_INFO(exp_info); + off_t pg_off; + int ret; + + ret = uverbs_get_const(&pg_off, attrs, UVERBS_ATTR_ALLOC_DMABUF_PGOFF); + if (ret) + return ret; + + mmap_entry = ib_dev->ops.pgoff_to_mmap_entry(attrs->context, pg_off); + if (!mmap_entry) + return -EINVAL; + + ret = ib_dev->ops.mmap_get_pfns(mmap_entry, &uverbs_dmabuf->phys_vec, + &uverbs_dmabuf->provider); + if (ret) + goto err; + + exp_info.ops = &uverbs_dmabuf_ops; + exp_info.size = uverbs_dmabuf->phys_vec.len; + exp_info.flags = O_CLOEXEC; + exp_info.priv = uverbs_dmabuf; + + uverbs_dmabuf->dmabuf = dma_buf_export(&exp_info); + if (IS_ERR(uverbs_dmabuf->dmabuf)) { + ret = PTR_ERR(uverbs_dmabuf->dmabuf); + goto err; + } + + INIT_LIST_HEAD(&uverbs_dmabuf->dmabufs_elm); + mutex_lock(&mmap_entry->dmabufs_lock); + if (mmap_entry->driver_removed) + ret = -EIO; + else + list_add_tail(&uverbs_dmabuf->dmabufs_elm, &mmap_entry->dmabufs); + mutex_unlock(&mmap_entry->dmabufs_lock); + if (ret) + goto err_revoked; + + uobj->object = uverbs_dmabuf->dmabuf->file; + uverbs_dmabuf->mmap_entry = mmap_entry; + uverbs_finalize_uobj_create(attrs, UVERBS_ATTR_ALLOC_DMABUF_HANDLE); + return 0; + +err_revoked: + dma_buf_put(uverbs_dmabuf->dmabuf); +err: + rdma_user_mmap_entry_put(mmap_entry); + return ret; +} + +DECLARE_UVERBS_NAMED_METHOD( + UVERBS_METHOD_DMABUF_ALLOC, + UVERBS_ATTR_FD(UVERBS_ATTR_ALLOC_DMABUF_HANDLE, + UVERBS_OBJECT_DMABUF, + UVERBS_ACCESS_NEW, + UA_MANDATORY), + UVERBS_ATTR_PTR_IN(UVERBS_ATTR_ALLOC_DMABUF_PGOFF, + UVERBS_ATTR_TYPE(u64), + UA_MANDATORY)); + +static void uverbs_dmabuf_fd_destroy_uobj(struct ib_uobject *uobj, + enum rdma_remove_reason why) +{ + struct ib_uverbs_dmabuf_file *uverbs_dmabuf = + container_of(uobj, struct ib_uverbs_dmabuf_file, uobj); + + mutex_lock(&uverbs_dmabuf->mmap_entry->dmabufs_lock); + dma_resv_lock(uverbs_dmabuf->dmabuf->resv, NULL); + if (!uverbs_dmabuf->revoked) { + uverbs_dmabuf->revoked = true; + list_del(&uverbs_dmabuf->dmabufs_elm); + dma_buf_move_notify(uverbs_dmabuf->dmabuf); + } + dma_resv_unlock(uverbs_dmabuf->dmabuf->resv); + mutex_unlock(&uverbs_dmabuf->mmap_entry->dmabufs_lock); + + /* Matches the get done as part of pgoff_to_mmap_entry() */ + rdma_user_mmap_entry_put(uverbs_dmabuf->mmap_entry); +}; + +DECLARE_UVERBS_NAMED_OBJECT( + UVERBS_OBJECT_DMABUF, + UVERBS_TYPE_ALLOC_FD(sizeof(struct ib_uverbs_dmabuf_file), + uverbs_dmabuf_fd_destroy_uobj, + NULL, NULL, O_RDONLY), + &UVERBS_METHOD(UVERBS_METHOD_DMABUF_ALLOC)); + +const struct uapi_definition uverbs_def_obj_dmabuf[] = { + UAPI_DEF_CHAIN_OBJ_TREE_NAMED(UVERBS_OBJECT_DMABUF), + UAPI_DEF_OBJ_NEEDS_FN(mmap_get_pfns), + UAPI_DEF_OBJ_NEEDS_FN(pgoff_to_mmap_entry), + {} +}; diff --git a/drivers/infiniband/core/uverbs_uapi.c b/drivers/infiniband/core/uverbs_uapi.c index e00ea63175bd..38d0bbbee796 100644 --- a/drivers/infiniband/core/uverbs_uapi.c +++ b/drivers/infiniband/core/uverbs_uapi.c @@ -631,6 +631,7 @@ static const struct uapi_definition uverbs_core_api[] = { UAPI_DEF_CHAIN(uverbs_def_obj_cq), UAPI_DEF_CHAIN(uverbs_def_obj_device), UAPI_DEF_CHAIN(uverbs_def_obj_dm), + UAPI_DEF_CHAIN(uverbs_def_obj_dmabuf), UAPI_DEF_CHAIN(uverbs_def_obj_dmah), UAPI_DEF_CHAIN(uverbs_def_obj_flow_action), UAPI_DEF_CHAIN(uverbs_def_obj_intf), diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index 6c372a37c482..5be67013c8ae 100644 --- a/include/rdma/ib_verbs.h +++ b/include/rdma/ib_verbs.h @@ -43,6 +43,7 @@ #include <uapi/rdma/rdma_user_ioctl.h> #include <uapi/rdma/ib_user_ioctl_verbs.h> #include <linux/pci-tph.h> +#include <linux/dma-buf.h>

#define IB_FW_VERSION_NAME_MAX ETHTOOL_FWVERS_LEN

@@ -2363,6 +2364,9 @@ struct rdma_user_mmap_entry { unsigned long start_pgoff; size_t npages; bool driver_removed; + /* protects access to dmabufs */ + struct mutex dmabufs_lock; + struct list_head dmabufs; };

/* Return the offset (in bytes) the user should pass to libc's mmap() */ @@ -2500,6 +2504,11 @@ struct ib_device_ops { * Therefore needs to be implemented by the driver in mmap_free. */ void (*mmap_free)(struct rdma_user_mmap_entry *entry); + int (*mmap_get_pfns)(struct rdma_user_mmap_entry *entry, + struct dma_buf_phys_vec *phys_vec, + struct p2pdma_provider **provider); + struct rdma_user_mmap_entry *(*pgoff_to_mmap_entry)(struct ib_ucontext *ucontext, + off_t pg_off); void (*disassociate_ucontext)(struct ib_ucontext *ibcontext); int (*alloc_pd)(struct ib_pd *pd, struct ib_udata *udata); int (*dealloc_pd)(struct ib_pd *pd, struct ib_udata *udata); diff --git a/include/rdma/uverbs_types.h b/include/rdma/uverbs_types.h index 26ba919ac245..6a253b7dc5ea 100644 --- a/include/rdma/uverbs_types.h +++ b/include/rdma/uverbs_types.h @@ -186,6 +186,7 @@ struct ib_uverbs_file { extern const struct uverbs_obj_type_class uverbs_idr_class; extern const struct uverbs_obj_type_class uverbs_fd_class; int uverbs_uobject_fd_release(struct inode *inode, struct file *filp); +int uverbs_uobject_release(struct ib_uobject *uobj);

#define UVERBS_BUILD_BUG_ON(cond) (sizeof(char[1 - 2 * !!(cond)]) - \ sizeof(char)) diff --git a/include/uapi/rdma/ib_user_ioctl_cmds.h b/include/uapi/rdma/ib_user_ioctl_cmds.h index 35da4026f452..72041c1b0ea5 100644 --- a/include/uapi/rdma/ib_user_ioctl_cmds.h +++ b/include/uapi/rdma/ib_user_ioctl_cmds.h @@ -56,6 +56,7 @@ enum uverbs_default_objects { UVERBS_OBJECT_COUNTERS, UVERBS_OBJECT_ASYNC_EVENT, UVERBS_OBJECT_DMAH, + UVERBS_OBJECT_DMABUF, };

enum { @@ -263,6 +264,15 @@ enum uverbs_methods_dmah { UVERBS_METHOD_DMAH_FREE, };

+enum uverbs_attrs_alloc_dmabuf_cmd_attr_ids { + UVERBS_ATTR_ALLOC_DMABUF_HANDLE, + UVERBS_ATTR_ALLOC_DMABUF_PGOFF, +}; + +enum uverbs_methods_dmabuf { + UVERBS_METHOD_DMABUF_ALLOC, +}; + enum uverbs_attrs_reg_dm_mr_cmd_attr_ids { UVERBS_ATTR_REG_DM_MR_HANDLE, UVERBS_ATTR_REG_DM_MR_OFFSET,