[PATCH io_uring-7.1 05/16] io_uring/zcrx: implement device-less mode for zcrx
From: Pavel Begunkov <asml.silence@gmail.com>
Date: 2026-03-23 12:44:10
Also in:
io-uring
Subsystem:
io_uring, io_uring zcrx, the rest · Maintainers:
Jens Axboe, Pavel Begunkov, Linus Torvalds
Allow creating a zcrx instance without attaching it to a net device. All data will be copied through the fallback path. The user is also expected to use ZCRX_CTRL_FLUSH_RQ to handle overflows as it normally should even with a netdev, but it becomes even more relevant as there will likely be no one to automatically pick up buffers. Apart from that, it follows the zcrx uapi for the I/O path, and is useful for testing, experimentation, and potentially for the copy recieve path in the future if improved. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> --- include/uapi/linux/io_uring/zcrx.h | 9 ++++++- io_uring/zcrx.c | 41 ++++++++++++++++++++---------- io_uring/zcrx.h | 2 +- 3 files changed, 36 insertions(+), 16 deletions(-)
diff --git a/include/uapi/linux/io_uring/zcrx.h b/include/uapi/linux/io_uring/zcrx.h
index 3163a4b8aeb0..103d65e690eb 100644
--- a/include/uapi/linux/io_uring/zcrx.h
+++ b/include/uapi/linux/io_uring/zcrx.h@@ -49,7 +49,14 @@ struct io_uring_zcrx_area_reg { }; enum zcrx_reg_flags { - ZCRX_REG_IMPORT = 1, + ZCRX_REG_IMPORT = 1, + + /* + * Register a zcrx instance without a net device. All data will be + * copied. The refill queue entries might not be automatically + * consmumed and need to be flushed, see ZCRX_CTRL_FLUSH_RQ. + */ + ZCRX_REG_NODEV = 2, }; enum zcrx_features {
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index d2798a82c678..d772e1609c4b 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c@@ -127,10 +127,10 @@ static int io_import_dmabuf(struct io_zcrx_ifq *ifq, int dmabuf_fd = area_reg->dmabuf_fd; int i, ret; + if (!ifq->dev) + return -EINVAL; if (off) return -EINVAL; - if (WARN_ON_ONCE(!ifq->dev)) - return -EFAULT; if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER)) return -EINVAL;
@@ -211,11 +211,13 @@ static int io_import_umem(struct io_zcrx_ifq *ifq, if (ret) goto out_err; - ret = dma_map_sgtable(ifq->dev, &mem->page_sg_table, - DMA_FROM_DEVICE, IO_DMA_ATTR); - if (ret < 0) - goto out_err; - mapped = true; + if (ifq->dev) { + ret = dma_map_sgtable(ifq->dev, &mem->page_sg_table, + DMA_FROM_DEVICE, IO_DMA_ATTR); + if (ret < 0) + goto out_err; + mapped = true; + } mem->account_pages = io_count_account_pages(pages, nr_pages); ret = io_account_mem(ifq->user, ifq->mm_account, mem->account_pages);
@@ -450,7 +452,8 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq, ret = io_import_area(ifq, &area->mem, area_reg); if (ret) goto err; - area->is_mapped = true; + if (ifq->dev) + area->is_mapped = true; if (buf_size_shift > io_area_max_shift(&area->mem)) { ret = -ERANGE;
@@ -486,9 +489,11 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq, niov->type = NET_IOV_IOURING; } - ret = io_populate_area_dma(ifq, area); - if (ret) - goto err; + if (ifq->dev) { + ret = io_populate_area_dma(ifq, area); + if (ret) + goto err; + } area->free_count = nr_iovs; /* we're only supporting one area per ifq for now */
@@ -826,6 +831,8 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx, return -EFAULT; if (reg.if_rxq == -1 || !reg.rq_entries) return -EINVAL; + if ((reg.if_rxq || reg.if_idx) && (reg.flags & ZCRX_REG_NODEV)) + return -EINVAL; if (reg.rq_entries > IO_RQ_MAX_ENTRIES) { if (!(ctx->flags & IORING_SETUP_CLAMP)) return -EINVAL;
@@ -861,9 +868,15 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx, if (ret) goto err; - ret = zcrx_register_netdev(ifq, ®, &area); - if (ret) - goto err; + if (!(reg.flags & ZCRX_REG_NODEV)) { + ret = zcrx_register_netdev(ifq, ®, &area); + if (ret) + goto err; + } else { + ret = io_zcrx_create_area(ifq, &area, ®); + if (ret) + goto err; + } reg.zcrx_id = id;
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 0316a41a3561..f395656c3160 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h@@ -8,7 +8,7 @@ #include <net/page_pool/types.h> #include <net/net_trackers.h> -#define ZCRX_SUPPORTED_REG_FLAGS (ZCRX_REG_IMPORT) +#define ZCRX_SUPPORTED_REG_FLAGS (ZCRX_REG_IMPORT | ZCRX_REG_NODEV) #define ZCRX_FEATURES (ZCRX_FEATURE_RX_PAGE_SIZE) struct io_zcrx_mem {
--
2.53.0