libibverbs: Add DMA-buf fd export for ibv_buf#1770
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July 14, 2026 16:41
Add ibv_export_buf_dmabuf_fd() so applications can obtain a caller-owned DMA-buf file descriptor from provider-aware buffers that are backed by DMA-buf memory. Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Allow Python users to retrieve a caller-owned DMA-buf file descriptor from a Buf's backing memory. Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Add buffer API checks for successful fd export on DMA-buf backed buffers and ENODATA on ordinary memory buffers. Signed-off-by: Jiri Pirko <jiri@nvidia.com>
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Jul 18, 2026
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| int ibv_export_buf_dmabuf_fd(struct ibv_buf *buf) | ||
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| if (buf->dmabuf_fd < 0) { |
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I wonder how do you feel about a potential view that this conflates (1) *buf is backed by VA, and (2) dmabuf *buf has a bad fd ?
Thinking of sth like enum ibv_buf_alloc_type alloc_type; as part of ibv_buf, so we return EOPNOTSUPP on .type != IBV_BUF_ALLOC_TYPE_DMABUF, and ENODATA on bad dmabuf fd.
But not having a .type within ibv_but does keep it simple, and distinguishing between (1) and (2) may not add much value.
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If buf is backed by VA, dmabuf_fd is -1. That case is covered.
not sure what you mean by "a bad fd".
Yeah, I agree. In some original internal implementation I actually had "type", but removed that as it really brought no value.
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Summary
Add
ibv_export_buf_dmabuf_fd()so applications can pass DMA-buf-backed provider allocations to APIs that import DMA-buf file descriptors.Expose it through pyverbs, document the API, and add test coverage.