ibv_alloc_buf(3)

NAME
ibv_alloc_buf, ibv_free_buf, ibv_reg_buf_mr - allocate provider-aware buffers and register them as memory regions

SYNOPSIS

        #include <infiniband/verbs.h>
        void *ibv_alloc_buf(struct ibv_pd *pd, size_t size, struct ibv_buf **buf);
        void ibv_free_buf(struct ibv_buf *buf);
        struct ibv_mr *ibv_reg_buf_mr(struct ibv_pd *pd, struct ibv_buf *buf, void *addr,
                                      size_t length, int access);

DESCRIPTION
ibv_alloc_buf() allocates a buffer using the allocation method selected by the provider for the protection domain pd. On success it returns the mapped address and stores an opaque buffer handle in buf. The handle is used by ibv_free_buf(), ibv_reg_buf_mr(), and ibv_reg_mr_ex() with IBV_REG_MR_MASK_BUF, and must not be interpreted by applications.

ibv_free_buf() releases a buffer handle returned by ibv_alloc_buf(). The protection domain used for allocation must remain valid until the buffer is freed.

ibv_reg_buf_mr() registers a memory region for a buffer returned by ibv_alloc_buf(). Applications can register the same buffer through ibv_reg_mr_ex() by setting both IBV_REG_MR_MASK_BUF and IBV_REG_MR_MASK_ADDR, passing the buffer handle in mr_init_attr->buf and the address to register in mr_init_attr->addr. When IBV_REG_MR_MASK_BUF is set the caller must not set IBV_REG_MR_MASK_FD or IBV_REG_MR_MASK_FD_OFFSET, and, for a DMA-buf backed buffer, must not set IBV_REG_MR_MASK_IOVA; libibverbs derives these from the buffer handle and otherwise fails with EINVAL. The pd argument must be the same protection domain that was used to allocate the buffer. If a different protection domain is supplied, registration fails with EINVAL. For ordinary memory it behaves like ibv_reg_mr(). For provider allocations backed by a DMA-buf, it registers the corresponding DMA-buf range using the metadata stored in the opaque buf handle.

ARGUMENTS

pd  For ibv_alloc_buf(), the protection domain (or parent domain) to allocate from; its provider selects the buffer’s backing allocation method. It must remain valid until the buffer is freed with ibv_free_buf(). For ibv_reg_buf_mr(), the same protection domain that allocated buf (otherwise registration fails with EINVAL).

size
    Size of the buffer to allocate, in bytes (ibv_alloc_buf()).

buf For ibv_alloc_buf(), an output parameter set on success to an opaque buffer handle. For ibv_free_buf() and ibv_reg_buf_mr(), the buffer handle returned by ibv_alloc_buf() to be released or registered, respectively.

addr
    The start address to register (ibv_reg_buf_mr()): the buffer base returned by ibv_alloc_buf() or an address within that buffer.

length
    Length in bytes to register (ibv_reg_buf_mr()); addr + length must stay within the buffer.

access
    Access flags for the memory region (ibv_reg_buf_mr()), the same as for ibv_reg_mr().

RETURN VALUE
ibv_alloc_buf() returns the mapped buffer address on success, or NULL if the request fails.

ibv_reg_buf_mr() returns a pointer to the registered MR on success, or NULL if the request fails.

ibv_free_buf() does not return a value.

NOTES
Applications running in a CoCo guest that need unprotected/shared memory should first create a parent domain with IBV_PARENT_DOMAIN_INIT_ATTR_ALLOW_CC_UNPROTECTED_ALLOC, then use that parent domain as the pd argument to ibv_alloc_buf() and ibv_reg_buf_mr() (or ibv_reg_mr_ex() with IBV_REG_MR_MASK_BUF).

SEE ALSO
ibv_alloc_parent_domain(3), ibv_reg_mr(3), ibv_reg_mr_ex(3), ibv_reg_dmabuf_mr(3)