Re: [PATCH io_uring 0/5] Add dmabuf support for io_uring zcrx

[Alexey Charkov <alchark@gmail.com>]

On Tue, May 6, 2025 at 6:29 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> Currently, io_uring zcrx uses regular user pages to populate the
> area for page pools, this series allows the user to pass a dmabuf
> instead.
>
> Patches 1-4 are preparatory and do code shuffling. All dmabuf
> touching changes are in the last patch. A basic example can be
> found at:
>
> https://github.com/isilence/liburing/tree/zcrx-dmabuf
> https://github.com/isilence/liburing.git zcrx-dmabuf
>
> Pavel Begunkov (5):
>   io_uring/zcrx: improve area validation
>   io_uring/zcrx: resolve netdev before area creation
>   io_uring/zcrx: split out memory holders from area
>   io_uring/zcrx: split common area map/unmap parts
>   io_uring/zcrx: dmabuf backed zerocopy receive
>
>  include/uapi/linux/io_uring.h |   6 +-
>  io_uring/rsrc.c               |  27 ++--
>  io_uring/rsrc.h               |   2 +-
>  io_uring/zcrx.c               | 260 +++++++++++++++++++++++++++-------
>  io_uring/zcrx.h               |  18 ++-
>  5 files changed, 248 insertions(+), 65 deletions(-)

Hi Pavel,

Looks like another "depends" line might be needed in io_uring/Kconfig:

diff --git a/io_uring/Kconfig b/io_uring/Kconfig
index 4b949c42c0bf..9fa2cf502940 100644
--- a/io_uring/Kconfig
+++ b/io_uring/Kconfig
@@ -9,3 +9,4 @@ config IO_URING_ZCRX
        depends on PAGE_POOL
        depends on INET
        depends on NET_RX_BUSY_POLL
+       depends on DMA_SHARED_BUFFER

Otherwise I'm having trouble compiling the next-20250506 kernel for
VT8500, which doesn't select DMA_BUF by default. The following linking
error appears at the very end:

armv7a-unknown-linux-gnueabihf-ld: io_uring/zcrx.o: in function
`io_release_dmabuf':
zcrx.c:(.text+0x1c): undefined reference to `dma_buf_unmap_attachment_unlocked'
armv7a-unknown-linux-gnueabihf-ld: zcrx.c:(.text+0x30): undefined
reference to `dma_buf_detach'
armv7a-unknown-linux-gnueabihf-ld: zcrx.c:(.text+0x40): undefined
reference to `dma_buf_put'
armv7a-unknown-linux-gnueabihf-ld: io_uring/zcrx.o: in function
`io_register_zcrx_ifq':
zcrx.c:(.text+0x15cc): undefined reference to `dma_buf_get'
armv7a-unknown-linux-gnueabihf-ld: zcrx.c:(.text+0x15e8): undefined
reference to `dma_buf_attach'
armv7a-unknown-linux-gnueabihf-ld: zcrx.c:(.text+0x1604): undefined
reference to `dma_buf_map_attachment_unlocked'
make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux] Error 1
make[1]: *** [/home/alchark/linux/Makefile:1242: vmlinux] Error 2
make: *** [Makefile:248: __sub-make] Error 2

Best regards,
Alexey