[PATCH v14 00/11] io_uring zero copy rx

[PATCH v14 00/11] io_uring zero copy rx

[David Wei]

This patchset contains io_uring patches needed by a new io_uring request
implementing zero copy rx into userspace pages, eliminating a kernel to
user copy.

We configure a page pool that a driver uses to fill a hw rx queue to
hand out user pages instead of kernel pages. Any data that ends up
hitting this hw rx queue will thus be dma'd into userspace memory
directly, without needing to be bounced through kernel memory. 'Reading'
data out of a socket instead becomes a _notification_ mechanism, where
the kernel tells userspace where the data is. The overall approach is
similar to the devmem TCP proposal.

This relies on hw header/data split, flow steering and RSS to ensure
packet headers remain in kernel memory and only desired flows hit a hw
rx queue configured for zero copy. Configuring this is outside of the
scope of this patchset.

We share netdev core infra with devmem TCP. The main difference is that
io_uring is used for the uAPI and the lifetime of all objects are bound
to an io_uring instance. Data is 'read' using a new io_uring request
type. When done, data is returned via a new shared refill queue. A zero
copy page pool refills a hw rx queue from this refill queue directly. Of
course, the lifetime of these data buffers are managed by io_uring
rather than the networking stack, with different refcounting rules.

This patchset is the first step adding basic zero copy support. We will
extend this iteratively with new features e.g. dynamically allocated
zero copy areas, THP support, dmabuf support, improved copy fallback,
general optimisations and more.

In terms of netdev support, we're first targeting Broadcom bnxt. Patches
aren't included since Taehee Yoo has already sent a more comprehensive
patchset adding support in [1]. Google gve should already support this,
and Mellanox mlx5 support is WIP pending driver changes.

===========
Performance
===========

Note: Comparison with epoll + TCP_ZEROCOPY_RECEIVE isn't done yet.

Test setup:
* AMD EPYC 9454
* Broadcom BCM957508 200G
* Kernel v6.11 base [2]
* liburing fork [3]
* kperf fork [4]
* 4K MTU
* Single TCP flow

With application thread + net rx softirq pinned to _different_ cores:

+-------------------------------+
| epoll     | io_uring          |
|-----------|-------------------|
| 82.2 Gbps | 116.2 Gbps (+41%) |
+-------------------------------+

Pinned to _same_ core:

+-------------------------------+
| epoll     | io_uring          |
|-----------|-------------------|
| 62.6 Gbps | 80.9 Gbps (+29%)  |
+-------------------------------+

=====
Links
=====

Broadcom bnxt support:
[1]: https://lore.kernel.org/netdev/20241003160620.1521626-8-ap420073@gmail.com/

Linux kernel branch including io_uring bits:
[2]: https://github.com/isilence/linux.git zcrx/v13

liburing for testing:
[3]: https://github.com/isilence/liburing.git zcrx/next

kperf for testing:
[4]: https://git.kernel.dk/kperf.git

Changes in v14:
---------------
* Remove net-next in patch subjects
* Cast to struct sockaddr in selftest for bind() and connect()

Changes in v13:
---------------
io_uring
* Add missing ~IORING_ZCRX_AREA_MASK
* Update documentation
* Selftest changes
  * Remove ipv4 support
  * Use ethtool() instea dof cmd()

net
* Fix race between io_uring closing and netdev unregister
* Regenerate Netlink YAML

Changes in v12:
---------------
* Check nla_nest_start() errors
* Don't leak a netdev, add missing netdev_put()
* Warn on failed queue restart during close

Changes in v11:
---------------
* Add a shim provider helper for page_pool_set_dma_addr_netmem()
* Drop netdev in ->uninstall, pin struct device instead
* Add net_mp_open_rxq() and net_mp_close_rxq()
* Remove unneeded CFLAGS += -I/usr/include/ in selftest Makefile

Changes in v10:
---------------
* Fix !CONFIG_PAGE_POOL build
* Use acquire/release for RQ in examples
* Fix page_pool_ref_netmem for net_iov
* Move provider helpers / definitions into a new file
* Don’t export page_pool_{set,clear}_pp_info, introduce
  net_mp_niov_{set,clear}_page_pool() instead
* Remove devmem.h from net/core/page_pool_user.c
* Add Netdev yaml for io-uring attribute
* Add memory provider ops for filling in Netlink info

Changes in v9:
--------------
* Fail proof against multiple page pools running the same memory
  provider
  * Lock the consumer side of the refill queue.
  * Move scrub into io_uring exit.
  * Kill napi_execute.
  * Kill area init api and export finer grained net helpers as partial
    init now need to happen in ->alloc_netmems()
* Separate user refcounting.
  * Fix copy fallback path math.
* Add rodata check to page_pool_init()
* Fix incorrect path in documentation

Changes in v8:
--------------
* add documentation and selftest
* use io_uring regions for the refill ring

Changes in v7:
--------------
net:
* Use NAPI_F_PREFER_BUSY_POLL for napi_execute + stylistics changes.

Changes in v6:
--------------
Please note: Comparison with TCP_ZEROCOPY_RECEIVE isn't done yet.

net:
* Drop a devmem.h clean up patch.
* Migrate to netdev_get_by_index from deprecated API.
* Fix !CONFIG_NET_DEVMEM build.
* Don’t return into the page pool cache directly, use a new helper
* Refactor napi_execute

io_uring:
* Require IORING_RECV_MULTISHOT flag set.
* Add unselectable CONFIG_IO_URING_ZCRX.
* Pulled latest io_uring changes.
* Unexport io_uring_pp_zc_ops.

Changes in v5:
--------------
* Rebase on top of merged net_iov + netmem infra.
* Decouple net_iov from devmem TCP.
* Use netdev queue API to allocate an rx queue.
* Minor uAPI enhancements for future extensibility.
* QoS improvements with request throttling.

Changes in RFC v4:
------------------
* Rebased on top of Mina Almasry's TCP devmem patchset and latest
  net-next, now sharing common infra e.g.:
    * netmem_t and net_iovs
    * Page pool memory provider
* The registered buffer (rbuf) completion queue where completions from
  io_recvzc requests are posted is removed. Now these post into the main
  completion queue, using big (32-byte) CQEs. The first 16 bytes is an
  ordinary CQE, while the latter 16 bytes contain the io_uring_rbuf_cqe
  as before. This vastly simplifies the uAPI and removes a level of
  indirection in userspace when looking for payloads.
  * The rbuf refill queue is still needed for userspace to return
    buffers to kernel.
* Simplified code and uAPI on the io_uring side, particularly
  io_recvzc() and io_zc_rx_recv(). Many unnecessary lines were removed
  e.g. extra msg flags, readlen, etc.

Changes in RFC v3:
------------------
* Rebased on top of Jakub Kicinski's memory provider API RFC. The ZC
  pool added is now a backend for memory provider.
* We're also reusing ppiov infrastructure. The refcounting rules stay
  the same but it's shifted into ppiov->refcount. That lets us to
  flexibly manage buffer lifetimes without adding any extra code to the
  common networking paths. It'd also make it easier to support dmabufs
  and device memory in the future.
  * io_uring also knows about pages, and so ppiovs might unnecessarily
    break tools inspecting data, that can easily be solved later.

Many patches are not for upstream as they depend on work in progress,
namely from Mina:

* struct netmem_t
* Driver ndo commands for Rx queue configs
* struct page_pool_iov and shared pp infra

Changes in RFC v2:
------------------
* Added copy fallback support if userspace memory allocated for ZC Rx
  runs out, or if header splitting or flow steering fails.
* Added veth support for ZC Rx, for testing and demonstration. We will
  need to figure out what driver would be best for such testing
  functionality in the future. Perhaps netdevsim?
* Added socket registration API to io_uring to associate specific
  sockets with ifqs/Rx queues for ZC.
* Added multi-socket support, such that multiple connections can be
  steered into the same hardware Rx queue.
* Added Netbench server/client support.

David Wei (6):
  io_uring/zcrx: add interface queue and refill queue
  io_uring/zcrx: add io_zcrx_area
  io_uring/zcrx: add io_recvzc request
  io_uring/zcrx: set pp memory provider for an rx queue
  net: add documentation for io_uring zcrx
  io_uring/zcrx: add selftest

Pavel Begunkov (5):
  io_uring/zcrx: grab a net device
  io_uring/zcrx: implement zerocopy receive pp memory provider
  io_uring/zcrx: dma-map area for the device
  io_uring/zcrx: throttle receive requests
  io_uring/zcrx: add copy fallback

 Documentation/networking/index.rst            |   1 +
 Documentation/networking/iou-zcrx.rst         | 202 ++++
 Kconfig                                       |   2 +
 include/linux/io_uring_types.h                |   6 +
 include/uapi/linux/io_uring.h                 |  54 +-
 io_uring/KConfig                              |  10 +
 io_uring/Makefile                             |   1 +
 io_uring/io_uring.c                           |   7 +
 io_uring/io_uring.h                           |  10 +
 io_uring/memmap.h                             |   1 +
 io_uring/net.c                                |  74 ++
 io_uring/opdef.c                              |  16 +
 io_uring/register.c                           |   7 +
 io_uring/rsrc.c                               |   2 +-
 io_uring/rsrc.h                               |   1 +
 io_uring/zcrx.c                               | 954 ++++++++++++++++++
 io_uring/zcrx.h                               |  73 ++
 .../selftests/drivers/net/hw/.gitignore       |   2 +
 .../testing/selftests/drivers/net/hw/Makefile |   5 +
 .../selftests/drivers/net/hw/iou-zcrx.c       | 426 ++++++++
 .../selftests/drivers/net/hw/iou-zcrx.py      |  64 ++
 21 files changed, 1916 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/networking/iou-zcrx.rst
 create mode 100644 io_uring/KConfig
 create mode 100644 io_uring/zcrx.c
 create mode 100644 io_uring/zcrx.h
 create mode 100644 tools/testing/selftests/drivers/net/hw/iou-zcrx.c
 create mode 100755 tools/testing/selftests/drivers/net/hw/iou-zcrx.py

-- 
2.43.5

[PATCH v14 01/11] io_uring/zcrx: add interface queue and refill queue

[David Wei]

Add a new object called an interface queue (ifq) that represents a net
rx queue that has been configured for zero copy. Each ifq is registered
using a new registration opcode IORING_REGISTER_ZCRX_IFQ.

The refill queue is allocated by the kernel and mapped by userspace
using a new offset IORING_OFF_RQ_RING, in a similar fashion to the main
SQ/CQ. It is used by userspace to return buffers that it is done with,
which will then be re-used by the netdev again.

The main CQ ring is used to notify userspace of received data by using
the upper 16 bytes of a big CQE as a new struct io_uring_zcrx_cqe. Each
entry contains the offset + len to the data.

For now, each io_uring instance only has a single ifq.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 Kconfig                        |   2 +
 include/linux/io_uring_types.h |   6 ++
 include/uapi/linux/io_uring.h  |  43 +++++++++-
 io_uring/KConfig               |  10 +++
 io_uring/Makefile              |   1 +
 io_uring/io_uring.c            |   7 ++
 io_uring/memmap.h              |   1 +
 io_uring/register.c            |   7 ++
 io_uring/zcrx.c                | 149 +++++++++++++++++++++++++++++++++
 io_uring/zcrx.h                |  35 ++++++++
 10 files changed, 260 insertions(+), 1 deletion(-)
 create mode 100644 io_uring/KConfig
 create mode 100644 io_uring/zcrx.c
 create mode 100644 io_uring/zcrx.h

diff --git a/Kconfig b/Kconfig
index 745bc773f567..529ea7694ba9 100644
--- a/Kconfig
+++ b/Kconfig
@@ -30,3 +30,5 @@ source "lib/Kconfig"
 source "lib/Kconfig.debug"
 
 source "Documentation/Kconfig"
+
+source "io_uring/KConfig"
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index e2fef264ff8b..7bf478727a31 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -40,6 +40,8 @@ enum io_uring_cmd_flags {
 	IO_URING_F_TASK_DEAD		= (1 << 13),
 };
 
+struct io_zcrx_ifq;
+
 struct io_wq_work_node {
 	struct io_wq_work_node *next;
 };
@@ -382,6 +384,8 @@ struct io_ring_ctx {
 	struct wait_queue_head		poll_wq;
 	struct io_restriction		restrictions;
 
+	struct io_zcrx_ifq		*ifq;
+
 	u32			pers_next;
 	struct xarray		personalities;
 
@@ -434,6 +438,8 @@ struct io_ring_ctx {
 	struct io_mapped_region		ring_region;
 	/* used for optimised request parameter and wait argument passing  */
 	struct io_mapped_region		param_region;
+	/* just one zcrx per ring for now, will move to io_zcrx_ifq eventually */
+	struct io_mapped_region		zcrx_region;
 };
 
 struct io_tw_state {
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index e11c82638527..6a1632d0fba1 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -639,7 +639,8 @@ enum io_uring_register_op {
 	/* send MSG_RING without having a ring */
 	IORING_REGISTER_SEND_MSG_RING		= 31,
 
-	/* 32 reserved for zc rx */
+	/* register a netdev hw rx queue for zerocopy */
+	IORING_REGISTER_ZCRX_IFQ		= 32,
 
 	/* resize CQ ring */
 	IORING_REGISTER_RESIZE_RINGS		= 33,
@@ -956,6 +957,46 @@ enum io_uring_socket_op {
 	SOCKET_URING_OP_SETSOCKOPT,
 };
 
+/* Zero copy receive refill queue entry */
+struct io_uring_zcrx_rqe {
+	__u64	off;
+	__u32	len;
+	__u32	__pad;
+};
+
+struct io_uring_zcrx_cqe {
+	__u64	off;
+	__u64	__pad;
+};
+
+/* The bit from which area id is encoded into offsets */
+#define IORING_ZCRX_AREA_SHIFT	48
+#define IORING_ZCRX_AREA_MASK	(~(((__u64)1 << IORING_ZCRX_AREA_SHIFT) - 1))
+
+struct io_uring_zcrx_offsets {
+	__u32	head;
+	__u32	tail;
+	__u32	rqes;
+	__u32	__resv2;
+	__u64	__resv[2];
+};
+
+/*
+ * Argument for IORING_REGISTER_ZCRX_IFQ
+ */
+struct io_uring_zcrx_ifq_reg {
+	__u32	if_idx;
+	__u32	if_rxq;
+	__u32	rq_entries;
+	__u32	flags;
+
+	__u64	area_ptr; /* pointer to struct io_uring_zcrx_area_reg */
+	__u64	region_ptr; /* struct io_uring_region_desc * */
+
+	struct io_uring_zcrx_offsets offsets;
+	__u64	__resv[4];
+};
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/io_uring/KConfig b/io_uring/KConfig
new file mode 100644
index 000000000000..9e2a4beba1ef
--- /dev/null
+++ b/io_uring/KConfig
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# io_uring configuration
+#
+
+config IO_URING_ZCRX
+	def_bool y
+	depends on PAGE_POOL
+	depends on INET
+	depends on NET_RX_BUSY_POLL
diff --git a/io_uring/Makefile b/io_uring/Makefile
index d695b60dba4f..98e48339d84d 100644
--- a/io_uring/Makefile
+++ b/io_uring/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_IO_URING)		+= io_uring.o opdef.o kbuf.o rsrc.o notif.o \
 					epoll.o statx.o timeout.o fdinfo.o \
 					cancel.o waitid.o register.o \
 					truncate.o memmap.o alloc_cache.o
+obj-$(CONFIG_IO_URING_ZCRX)	+= zcrx.o
 obj-$(CONFIG_IO_WQ)		+= io-wq.o
 obj-$(CONFIG_FUTEX)		+= futex.o
 obj-$(CONFIG_NET_RX_BUSY_POLL) += napi.o
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index ec98a0ec6f34..7c34b5459e2d 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -97,6 +97,7 @@
 #include "uring_cmd.h"
 #include "msg_ring.h"
 #include "memmap.h"
+#include "zcrx.h"
 
 #include "timeout.h"
 #include "poll.h"
@@ -2700,6 +2701,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	mutex_lock(&ctx->uring_lock);
 	io_sqe_buffers_unregister(ctx);
 	io_sqe_files_unregister(ctx);
+	io_unregister_zcrx_ifqs(ctx);
 	io_cqring_overflow_kill(ctx);
 	io_eventfd_unregister(ctx);
 	io_free_alloc_caches(ctx);
@@ -2859,6 +2861,11 @@ static __cold void io_ring_exit_work(struct work_struct *work)
 			io_cqring_overflow_kill(ctx);
 			mutex_unlock(&ctx->uring_lock);
 		}
+		if (ctx->ifq) {
+			mutex_lock(&ctx->uring_lock);
+			io_shutdown_zcrx_ifqs(ctx);
+			mutex_unlock(&ctx->uring_lock);
+		}
 
 		if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
 			io_move_task_work_from_local(ctx);
diff --git a/io_uring/memmap.h b/io_uring/memmap.h
index c898dcba2b4e..dad0aa5b1b45 100644
--- a/io_uring/memmap.h
+++ b/io_uring/memmap.h
@@ -2,6 +2,7 @@
 #define IO_URING_MEMMAP_H
 
 #define IORING_MAP_OFF_PARAM_REGION		0x20000000ULL
+#define IORING_MAP_OFF_ZCRX_REGION		0x30000000ULL
 
 struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages);
 
diff --git a/io_uring/register.c b/io_uring/register.c
index 9a4d2fbce4ae..cc23a4c205cd 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -30,6 +30,7 @@
 #include "eventfd.h"
 #include "msg_ring.h"
 #include "memmap.h"
+#include "zcrx.h"
 
 #define IORING_MAX_RESTRICTIONS	(IORING_RESTRICTION_LAST + \
 				 IORING_REGISTER_LAST + IORING_OP_LAST)
@@ -813,6 +814,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_register_clone_buffers(ctx, arg);
 		break;
+	case IORING_REGISTER_ZCRX_IFQ:
+		ret = -EINVAL;
+		if (!arg || nr_args != 1)
+			break;
+		ret = io_register_zcrx_ifq(ctx, arg);
+		break;
 	case IORING_REGISTER_RESIZE_RINGS:
 		ret = -EINVAL;
 		if (!arg || nr_args != 1)
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
new file mode 100644
index 000000000000..f3ace7e8264d
--- /dev/null
+++ b/io_uring/zcrx.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "kbuf.h"
+#include "memmap.h"
+#include "zcrx.h"
+
+#define IO_RQ_MAX_ENTRIES		32768
+
+static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
+				 struct io_uring_zcrx_ifq_reg *reg,
+				 struct io_uring_region_desc *rd)
+{
+	size_t off, size;
+	void *ptr;
+	int ret;
+
+	off = sizeof(struct io_uring);
+	size = off + sizeof(struct io_uring_zcrx_rqe) * reg->rq_entries;
+	if (size > rd->size)
+		return -EINVAL;
+
+	ret = io_create_region_mmap_safe(ifq->ctx, &ifq->ctx->zcrx_region, rd,
+					 IORING_MAP_OFF_ZCRX_REGION);
+	if (ret < 0)
+		return ret;
+
+	ptr = io_region_get_ptr(&ifq->ctx->zcrx_region);
+	ifq->rq_ring = (struct io_uring *)ptr;
+	ifq->rqes = (struct io_uring_zcrx_rqe *)(ptr + off);
+	return 0;
+}
+
+static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
+{
+	io_free_region(ifq->ctx, &ifq->ctx->zcrx_region);
+	ifq->rq_ring = NULL;
+	ifq->rqes = NULL;
+}
+
+static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
+{
+	struct io_zcrx_ifq *ifq;
+
+	ifq = kzalloc(sizeof(*ifq), GFP_KERNEL);
+	if (!ifq)
+		return NULL;
+
+	ifq->if_rxq = -1;
+	ifq->ctx = ctx;
+	return ifq;
+}
+
+static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
+{
+	io_free_rbuf_ring(ifq);
+	kfree(ifq);
+}
+
+int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
+			  struct io_uring_zcrx_ifq_reg __user *arg)
+{
+	struct io_uring_zcrx_ifq_reg reg;
+	struct io_uring_region_desc rd;
+	struct io_zcrx_ifq *ifq;
+	int ret;
+
+	/*
+	 * 1. Interface queue allocation.
+	 * 2. It can observe data destined for sockets of other tasks.
+	 */
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	/* mandatory io_uring features for zc rx */
+	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN &&
+	      ctx->flags & IORING_SETUP_CQE32))
+		return -EINVAL;
+	if (ctx->ifq)
+		return -EBUSY;
+	if (copy_from_user(&reg, arg, sizeof(reg)))
+		return -EFAULT;
+	if (copy_from_user(&rd, u64_to_user_ptr(reg.region_ptr), sizeof(rd)))
+		return -EFAULT;
+	if (memchr_inv(&reg.__resv, 0, sizeof(reg.__resv)))
+		return -EINVAL;
+	if (reg.if_rxq == -1 || !reg.rq_entries || reg.flags)
+		return -EINVAL;
+	if (reg.rq_entries > IO_RQ_MAX_ENTRIES) {
+		if (!(ctx->flags & IORING_SETUP_CLAMP))
+			return -EINVAL;
+		reg.rq_entries = IO_RQ_MAX_ENTRIES;
+	}
+	reg.rq_entries = roundup_pow_of_two(reg.rq_entries);
+
+	if (!reg.area_ptr)
+		return -EFAULT;
+
+	ifq = io_zcrx_ifq_alloc(ctx);
+	if (!ifq)
+		return -ENOMEM;
+
+	ret = io_allocate_rbuf_ring(ifq, &reg, &rd);
+	if (ret)
+		goto err;
+
+	ifq->rq_entries = reg.rq_entries;
+	ifq->if_rxq = reg.if_rxq;
+
+	reg.offsets.rqes = sizeof(struct io_uring);
+	reg.offsets.head = offsetof(struct io_uring, head);
+	reg.offsets.tail = offsetof(struct io_uring, tail);
+
+	if (copy_to_user(arg, &reg, sizeof(reg)) ||
+	    copy_to_user(u64_to_user_ptr(reg.region_ptr), &rd, sizeof(rd))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	ctx->ifq = ifq;
+	return 0;
+err:
+	io_zcrx_ifq_free(ifq);
+	return ret;
+}
+
+void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
+{
+	struct io_zcrx_ifq *ifq = ctx->ifq;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	if (!ifq)
+		return;
+
+	ctx->ifq = NULL;
+	io_zcrx_ifq_free(ifq);
+}
+
+void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
+{
+	lockdep_assert_held(&ctx->uring_lock);
+}
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
new file mode 100644
index 000000000000..58e4ab6c6083
--- /dev/null
+++ b/io_uring/zcrx.h
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_ZC_RX_H
+#define IOU_ZC_RX_H
+
+#include <linux/io_uring_types.h>
+
+struct io_zcrx_ifq {
+	struct io_ring_ctx		*ctx;
+	struct io_uring			*rq_ring;
+	struct io_uring_zcrx_rqe	*rqes;
+	u32				rq_entries;
+
+	u32				if_rxq;
+};
+
+#if defined(CONFIG_IO_URING_ZCRX)
+int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
+			 struct io_uring_zcrx_ifq_reg __user *arg);
+void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx);
+void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx);
+#else
+static inline int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
+					struct io_uring_zcrx_ifq_reg __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+static inline void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
+{
+}
+static inline void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
+{
+}
+#endif
+
+#endif
-- 
2.43.5

[PATCH v14 02/11] io_uring/zcrx: add io_zcrx_area

[David Wei]

Add io_zcrx_area that represents a region of userspace memory that is
used for zero copy. During ifq registration, userspace passes in the
uaddr and len of userspace memory, which is then pinned by the kernel.
Each net_iov is mapped to one of these pages.

The freelist is a spinlock protected list that keeps track of all the
net_iovs/pages that aren't used.

For now, there is only one area per ifq and area registration happens
implicitly as part of ifq registration. There is no API for
adding/removing areas yet. The struct for area registration is there for
future extensibility once we support multiple areas and TCP devmem.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 include/uapi/linux/io_uring.h |  9 ++++
 io_uring/rsrc.c               |  2 +-
 io_uring/rsrc.h               |  1 +
 io_uring/zcrx.c               | 89 ++++++++++++++++++++++++++++++++++-
 io_uring/zcrx.h               | 16 +++++++
 5 files changed, 114 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 6a1632d0fba1..44844707d327 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -981,6 +981,15 @@ struct io_uring_zcrx_offsets {
 	__u64	__resv[2];
 };
 
+struct io_uring_zcrx_area_reg {
+	__u64	addr;
+	__u64	len;
+	__u64	rq_area_token;
+	__u32	flags;
+	__u32	__resv1;
+	__u64	__resv2[2];
+};
+
 /*
  * Argument for IORING_REGISTER_ZCRX_IFQ
  */
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index af39b69eb4fd..20b884c84e55 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -77,7 +77,7 @@ static int io_account_mem(struct io_ring_ctx *ctx, unsigned long nr_pages)
 	return 0;
 }
 
-static int io_buffer_validate(struct iovec *iov)
+int io_buffer_validate(struct iovec *iov)
 {
 	unsigned long tmp, acct_len = iov->iov_len + (PAGE_SIZE - 1);
 
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 190f7ee45de9..0f8c20246a74 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -68,6 +68,7 @@ int io_register_rsrc_update(struct io_ring_ctx *ctx, void __user *arg,
 			    unsigned size, unsigned type);
 int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
 			unsigned int size, unsigned int type);
+int io_buffer_validate(struct iovec *iov);
 
 bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
 			      struct io_imu_folio_data *data);
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index f3ace7e8264d..04883a3ae80c 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -10,6 +10,7 @@
 #include "kbuf.h"
 #include "memmap.h"
 #include "zcrx.h"
+#include "rsrc.h"
 
 #define IO_RQ_MAX_ENTRIES		32768
 
@@ -44,6 +45,79 @@ static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
 	ifq->rqes = NULL;
 }
 
+static void io_zcrx_free_area(struct io_zcrx_area *area)
+{
+	kvfree(area->freelist);
+	kvfree(area->nia.niovs);
+	if (area->pages) {
+		unpin_user_pages(area->pages, area->nia.num_niovs);
+		kvfree(area->pages);
+	}
+	kfree(area);
+}
+
+static int io_zcrx_create_area(struct io_zcrx_ifq *ifq,
+			       struct io_zcrx_area **res,
+			       struct io_uring_zcrx_area_reg *area_reg)
+{
+	struct io_zcrx_area *area;
+	int i, ret, nr_pages;
+	struct iovec iov;
+
+	if (area_reg->flags || area_reg->rq_area_token)
+		return -EINVAL;
+	if (area_reg->__resv1 || area_reg->__resv2[0] || area_reg->__resv2[1])
+		return -EINVAL;
+	if (area_reg->addr & ~PAGE_MASK || area_reg->len & ~PAGE_MASK)
+		return -EINVAL;
+
+	iov.iov_base = u64_to_user_ptr(area_reg->addr);
+	iov.iov_len = area_reg->len;
+	ret = io_buffer_validate(&iov);
+	if (ret)
+		return ret;
+
+	ret = -ENOMEM;
+	area = kzalloc(sizeof(*area), GFP_KERNEL);
+	if (!area)
+		goto err;
+
+	area->pages = io_pin_pages((unsigned long)area_reg->addr, area_reg->len,
+				   &nr_pages);
+	if (IS_ERR(area->pages)) {
+		ret = PTR_ERR(area->pages);
+		area->pages = NULL;
+		goto err;
+	}
+	area->nia.num_niovs = nr_pages;
+
+	area->nia.niovs = kvmalloc_array(nr_pages, sizeof(area->nia.niovs[0]),
+					 GFP_KERNEL | __GFP_ZERO);
+	if (!area->nia.niovs)
+		goto err;
+
+	area->freelist = kvmalloc_array(nr_pages, sizeof(area->freelist[0]),
+					GFP_KERNEL | __GFP_ZERO);
+	if (!area->freelist)
+		goto err;
+
+	for (i = 0; i < nr_pages; i++)
+		area->freelist[i] = i;
+
+	area->free_count = nr_pages;
+	area->ifq = ifq;
+	/* we're only supporting one area per ifq for now */
+	area->area_id = 0;
+	area_reg->rq_area_token = (u64)area->area_id << IORING_ZCRX_AREA_SHIFT;
+	spin_lock_init(&area->freelist_lock);
+	*res = area;
+	return 0;
+err:
+	if (area)
+		io_zcrx_free_area(area);
+	return ret;
+}
+
 static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 {
 	struct io_zcrx_ifq *ifq;
@@ -59,6 +133,9 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	if (ifq->area)
+		io_zcrx_free_area(ifq->area);
+
 	io_free_rbuf_ring(ifq);
 	kfree(ifq);
 }
@@ -66,6 +143,7 @@ static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 			  struct io_uring_zcrx_ifq_reg __user *arg)
 {
+	struct io_uring_zcrx_area_reg area;
 	struct io_uring_zcrx_ifq_reg reg;
 	struct io_uring_region_desc rd;
 	struct io_zcrx_ifq *ifq;
@@ -99,7 +177,7 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	}
 	reg.rq_entries = roundup_pow_of_two(reg.rq_entries);
 
-	if (!reg.area_ptr)
+	if (copy_from_user(&area, u64_to_user_ptr(reg.area_ptr), sizeof(area)))
 		return -EFAULT;
 
 	ifq = io_zcrx_ifq_alloc(ctx);
@@ -110,6 +188,10 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	if (ret)
 		goto err;
 
+	ret = io_zcrx_create_area(ifq, &ifq->area, &area);
+	if (ret)
+		goto err;
+
 	ifq->rq_entries = reg.rq_entries;
 	ifq->if_rxq = reg.if_rxq;
 
@@ -122,7 +204,10 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		ret = -EFAULT;
 		goto err;
 	}
-
+	if (copy_to_user(u64_to_user_ptr(reg.area_ptr), &area, sizeof(area))) {
+		ret = -EFAULT;
+		goto err;
+	}
 	ctx->ifq = ifq;
 	return 0;
 err:
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 58e4ab6c6083..53fd94b65b38 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -3,9 +3,25 @@
 #define IOU_ZC_RX_H
 
 #include <linux/io_uring_types.h>
+#include <net/page_pool/types.h>
+
+struct io_zcrx_area {
+	struct net_iov_area	nia;
+	struct io_zcrx_ifq	*ifq;
+
+	u16			area_id;
+	struct page		**pages;
+
+	/* freelist */
+	spinlock_t		freelist_lock ____cacheline_aligned_in_smp;
+	u32			free_count;
+	u32			*freelist;
+};
 
 struct io_zcrx_ifq {
 	struct io_ring_ctx		*ctx;
+	struct io_zcrx_area		*area;
+
 	struct io_uring			*rq_ring;
 	struct io_uring_zcrx_rqe	*rqes;
 	u32				rq_entries;
-- 
2.43.5

[PATCH v14 03/11] io_uring/zcrx: grab a net device

[David Wei]

From: Pavel Begunkov <asml.silence@gmail.com>

Zerocopy receive needs a net device to bind to its rx queue and dma map
buffers. As a preparation to following patches, resolve a net device
from the if_idx parameter with no functional changes otherwise.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 28 ++++++++++++++++++++++++++++
 io_uring/zcrx.h |  5 +++++
 2 files changed, 33 insertions(+)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 04883a3ae80c..435cd634f91c 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -3,6 +3,8 @@
 #include <linux/errno.h>
 #include <linux/mm.h>
 #include <linux/io_uring.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
 
 #include <uapi/linux/io_uring.h>
 
@@ -128,13 +130,28 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 
 	ifq->if_rxq = -1;
 	ifq->ctx = ctx;
+	spin_lock_init(&ifq->lock);
 	return ifq;
 }
 
+static void io_zcrx_drop_netdev(struct io_zcrx_ifq *ifq)
+{
+	spin_lock(&ifq->lock);
+	if (ifq->netdev) {
+		netdev_put(ifq->netdev, &ifq->netdev_tracker);
+		ifq->netdev = NULL;
+	}
+	spin_unlock(&ifq->lock);
+}
+
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	io_zcrx_drop_netdev(ifq);
+
 	if (ifq->area)
 		io_zcrx_free_area(ifq->area);
+	if (ifq->dev)
+		put_device(ifq->dev);
 
 	io_free_rbuf_ring(ifq);
 	kfree(ifq);
@@ -195,6 +212,17 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	ifq->rq_entries = reg.rq_entries;
 	ifq->if_rxq = reg.if_rxq;
 
+	ret = -ENODEV;
+	ifq->netdev = netdev_get_by_index(current->nsproxy->net_ns, reg.if_idx,
+					  &ifq->netdev_tracker, GFP_KERNEL);
+	if (!ifq->netdev)
+		goto err;
+
+	ifq->dev = ifq->netdev->dev.parent;
+	if (!ifq->dev)
+		return -EOPNOTSUPP;
+	get_device(ifq->dev);
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 53fd94b65b38..595bca0001d2 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -4,6 +4,7 @@
 
 #include <linux/io_uring_types.h>
 #include <net/page_pool/types.h>
+#include <net/net_trackers.h>
 
 struct io_zcrx_area {
 	struct net_iov_area	nia;
@@ -27,6 +28,10 @@ struct io_zcrx_ifq {
 	u32				rq_entries;
 
 	u32				if_rxq;
+	struct device			*dev;
+	struct net_device		*netdev;
+	netdevice_tracker		netdev_tracker;
+	spinlock_t			lock;
 };
 
 #if defined(CONFIG_IO_URING_ZCRX)
-- 
2.43.5

[PATCH v14 04/11] io_uring/zcrx: implement zerocopy receive pp memory provider

[David Wei]

From: Pavel Begunkov <asml.silence@gmail.com>

Implement a page pool memory provider for io_uring to receieve in a
zero copy fashion. For that, the provider allocates user pages wrapped
around into struct net_iovs, that are stored in a previously registered
struct net_iov_area.

Unlike the traditional receive, that frees pages and returns them back
to the page pool right after data was copied to the user, e.g. inside
recv(2), we extend the lifetime until the user space confirms that it's
done processing the data. That's done by taking a net_iov reference.
When the user is done with the buffer, it must return it back to the
kernel by posting an entry into the refill ring, which is usually polled
off the io_uring memory provider callback in the page pool's netmem
allocation path.

There is also a separate set of per net_iov "user" references accounting
whether a buffer is currently given to the user (including possible
fragmentation).

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 274 ++++++++++++++++++++++++++++++++++++++++++++++++
 io_uring/zcrx.h |   3 +
 2 files changed, 277 insertions(+)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 435cd634f91c..f9e924cfa829 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -2,10 +2,17 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
+#include <linux/nospec.h>
 #include <linux/io_uring.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
 
+#include <net/page_pool/helpers.h>
+#include <net/page_pool/memory_provider.h>
+#include <net/netlink.h>
+
+#include <trace/events/page_pool.h>
+
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
@@ -16,6 +23,33 @@
 
 #define IO_RQ_MAX_ENTRIES		32768
 
+__maybe_unused
+static const struct memory_provider_ops io_uring_pp_zc_ops;
+
+static inline struct io_zcrx_area *io_zcrx_iov_to_area(const struct net_iov *niov)
+{
+	struct net_iov_area *owner = net_iov_owner(niov);
+
+	return container_of(owner, struct io_zcrx_area, nia);
+}
+
+static inline atomic_t *io_get_user_counter(struct net_iov *niov)
+{
+	struct io_zcrx_area *area = io_zcrx_iov_to_area(niov);
+
+	return &area->user_refs[net_iov_idx(niov)];
+}
+
+static bool io_zcrx_put_niov_uref(struct net_iov *niov)
+{
+	atomic_t *uref = io_get_user_counter(niov);
+
+	if (unlikely(!atomic_read(uref)))
+		return false;
+	atomic_dec(uref);
+	return true;
+}
+
 static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 				 struct io_uring_zcrx_ifq_reg *reg,
 				 struct io_uring_region_desc *rd)
@@ -51,6 +85,7 @@ static void io_zcrx_free_area(struct io_zcrx_area *area)
 {
 	kvfree(area->freelist);
 	kvfree(area->nia.niovs);
+	kvfree(area->user_refs);
 	if (area->pages) {
 		unpin_user_pages(area->pages, area->nia.num_niovs);
 		kvfree(area->pages);
@@ -106,6 +141,19 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq,
 	for (i = 0; i < nr_pages; i++)
 		area->freelist[i] = i;
 
+	area->user_refs = kvmalloc_array(nr_pages, sizeof(area->user_refs[0]),
+					GFP_KERNEL | __GFP_ZERO);
+	if (!area->user_refs)
+		goto err;
+
+	for (i = 0; i < nr_pages; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+
+		niov->owner = &area->nia;
+		area->freelist[i] = i;
+		atomic_set(&area->user_refs[i], 0);
+	}
+
 	area->free_count = nr_pages;
 	area->ifq = ifq;
 	/* we're only supporting one area per ifq for now */
@@ -131,6 +179,7 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 	ifq->if_rxq = -1;
 	ifq->ctx = ctx;
 	spin_lock_init(&ifq->lock);
+	spin_lock_init(&ifq->rq_lock);
 	return ifq;
 }
 
@@ -256,7 +305,232 @@ void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
 	io_zcrx_ifq_free(ifq);
 }
 
+static struct net_iov *__io_zcrx_get_free_niov(struct io_zcrx_area *area)
+{
+	unsigned niov_idx;
+
+	lockdep_assert_held(&area->freelist_lock);
+
+	niov_idx = area->freelist[--area->free_count];
+	return &area->nia.niovs[niov_idx];
+}
+
+static void io_zcrx_return_niov_freelist(struct net_iov *niov)
+{
+	struct io_zcrx_area *area = io_zcrx_iov_to_area(niov);
+
+	spin_lock_bh(&area->freelist_lock);
+	area->freelist[area->free_count++] = net_iov_idx(niov);
+	spin_unlock_bh(&area->freelist_lock);
+}
+
+static void io_zcrx_return_niov(struct net_iov *niov)
+{
+	netmem_ref netmem = net_iov_to_netmem(niov);
+
+	page_pool_put_unrefed_netmem(niov->pp, netmem, -1, false);
+}
+
+static void io_zcrx_scrub(struct io_zcrx_ifq *ifq)
+{
+	struct io_zcrx_area *area = ifq->area;
+	int i;
+
+	if (!area)
+		return;
+
+	/* Reclaim back all buffers given to the user space. */
+	for (i = 0; i < area->nia.num_niovs; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+		int nr;
+
+		if (!atomic_read(io_get_user_counter(niov)))
+			continue;
+		nr = atomic_xchg(io_get_user_counter(niov), 0);
+		if (nr && !page_pool_unref_netmem(net_iov_to_netmem(niov), nr))
+			io_zcrx_return_niov(niov);
+	}
+}
+
 void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 {
 	lockdep_assert_held(&ctx->uring_lock);
+
+	if (ctx->ifq)
+		io_zcrx_scrub(ctx->ifq);
+}
+
+static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)
+{
+	u32 entries;
+
+	entries = smp_load_acquire(&ifq->rq_ring->tail) - ifq->cached_rq_head;
+	return min(entries, ifq->rq_entries);
 }
+
+static struct io_uring_zcrx_rqe *io_zcrx_get_rqe(struct io_zcrx_ifq *ifq,
+						 unsigned mask)
+{
+	unsigned int idx = ifq->cached_rq_head++ & mask;
+
+	return &ifq->rqes[idx];
+}
+
+static void io_zcrx_ring_refill(struct page_pool *pp,
+				struct io_zcrx_ifq *ifq)
+{
+	unsigned int mask = ifq->rq_entries - 1;
+	unsigned int entries;
+	netmem_ref netmem;
+
+	spin_lock_bh(&ifq->rq_lock);
+
+	entries = io_zcrx_rqring_entries(ifq);
+	entries = min_t(unsigned, entries, PP_ALLOC_CACHE_REFILL - pp->alloc.count);
+	if (unlikely(!entries)) {
+		spin_unlock_bh(&ifq->rq_lock);
+		return;
+	}
+
+	do {
+		struct io_uring_zcrx_rqe *rqe = io_zcrx_get_rqe(ifq, mask);
+		struct io_zcrx_area *area;
+		struct net_iov *niov;
+		unsigned niov_idx, area_idx;
+
+		area_idx = rqe->off >> IORING_ZCRX_AREA_SHIFT;
+		niov_idx = (rqe->off & ~IORING_ZCRX_AREA_MASK) >> PAGE_SHIFT;
+
+		if (unlikely(rqe->__pad || area_idx))
+			continue;
+		area = ifq->area;
+
+		if (unlikely(niov_idx >= area->nia.num_niovs))
+			continue;
+		niov_idx = array_index_nospec(niov_idx, area->nia.num_niovs);
+
+		niov = &area->nia.niovs[niov_idx];
+		if (!io_zcrx_put_niov_uref(niov))
+			continue;
+
+		netmem = net_iov_to_netmem(niov);
+		if (page_pool_unref_netmem(netmem, 1) != 0)
+			continue;
+
+		if (unlikely(niov->pp != pp)) {
+			io_zcrx_return_niov(niov);
+			continue;
+		}
+
+		net_mp_netmem_place_in_cache(pp, netmem);
+	} while (--entries);
+
+	smp_store_release(&ifq->rq_ring->head, ifq->cached_rq_head);
+	spin_unlock_bh(&ifq->rq_lock);
+}
+
+static void io_zcrx_refill_slow(struct page_pool *pp, struct io_zcrx_ifq *ifq)
+{
+	struct io_zcrx_area *area = ifq->area;
+
+	spin_lock_bh(&area->freelist_lock);
+	while (area->free_count && pp->alloc.count < PP_ALLOC_CACHE_REFILL) {
+		struct net_iov *niov = __io_zcrx_get_free_niov(area);
+		netmem_ref netmem = net_iov_to_netmem(niov);
+
+		net_mp_niov_set_page_pool(pp, niov);
+		net_mp_netmem_place_in_cache(pp, netmem);
+	}
+	spin_unlock_bh(&area->freelist_lock);
+}
+
+static netmem_ref io_pp_zc_alloc_netmems(struct page_pool *pp, gfp_t gfp)
+{
+	struct io_zcrx_ifq *ifq = pp->mp_priv;
+
+	/* pp should already be ensuring that */
+	if (unlikely(pp->alloc.count))
+		goto out_return;
+
+	io_zcrx_ring_refill(pp, ifq);
+	if (likely(pp->alloc.count))
+		goto out_return;
+
+	io_zcrx_refill_slow(pp, ifq);
+	if (!pp->alloc.count)
+		return 0;
+out_return:
+	return pp->alloc.cache[--pp->alloc.count];
+}
+
+static bool io_pp_zc_release_netmem(struct page_pool *pp, netmem_ref netmem)
+{
+	struct net_iov *niov;
+
+	if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))
+		return false;
+
+	niov = netmem_to_net_iov(netmem);
+	net_mp_niov_clear_page_pool(niov);
+	io_zcrx_return_niov_freelist(niov);
+	return false;
+}
+
+static int io_pp_zc_init(struct page_pool *pp)
+{
+	struct io_zcrx_ifq *ifq = pp->mp_priv;
+
+	if (WARN_ON_ONCE(!ifq))
+		return -EINVAL;
+	if (pp->dma_map)
+		return -EOPNOTSUPP;
+	if (pp->p.order != 0)
+		return -EOPNOTSUPP;
+
+	percpu_ref_get(&ifq->ctx->refs);
+	return 0;
+}
+
+static void io_pp_zc_destroy(struct page_pool *pp)
+{
+	struct io_zcrx_ifq *ifq = pp->mp_priv;
+	struct io_zcrx_area *area = ifq->area;
+
+	if (WARN_ON_ONCE(area->free_count != area->nia.num_niovs))
+		return;
+	percpu_ref_put(&ifq->ctx->refs);
+}
+
+static int io_pp_nl_fill(void *mp_priv, struct sk_buff *rsp,
+			 struct netdev_rx_queue *rxq)
+{
+	struct nlattr *nest;
+	int type;
+
+	type = rxq ? NETDEV_A_QUEUE_IO_URING : NETDEV_A_PAGE_POOL_IO_URING;
+	nest = nla_nest_start(rsp, type);
+	if (!nest)
+		return -EMSGSIZE;
+	nla_nest_end(rsp, nest);
+
+	return 0;
+}
+
+static void io_pp_uninstall(void *mp_priv, struct netdev_rx_queue *rxq)
+{
+	struct pp_memory_provider_params *p = &rxq->mp_params;
+	struct io_zcrx_ifq *ifq = mp_priv;
+
+	io_zcrx_drop_netdev(ifq);
+	p->mp_ops = NULL;
+	p->mp_priv = NULL;
+}
+
+static const struct memory_provider_ops io_uring_pp_zc_ops = {
+	.alloc_netmems		= io_pp_zc_alloc_netmems,
+	.release_netmem		= io_pp_zc_release_netmem,
+	.init			= io_pp_zc_init,
+	.destroy		= io_pp_zc_destroy,
+	.nl_fill		= io_pp_nl_fill,
+	.uninstall		= io_pp_uninstall,
+};
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 595bca0001d2..6c808240ac91 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -9,6 +9,7 @@
 struct io_zcrx_area {
 	struct net_iov_area	nia;
 	struct io_zcrx_ifq	*ifq;
+	atomic_t		*user_refs;
 
 	u16			area_id;
 	struct page		**pages;
@@ -26,6 +27,8 @@ struct io_zcrx_ifq {
 	struct io_uring			*rq_ring;
 	struct io_uring_zcrx_rqe	*rqes;
 	u32				rq_entries;
+	u32				cached_rq_head;
+	spinlock_t			rq_lock;
 
 	u32				if_rxq;
 	struct device			*dev;
-- 
2.43.5

[PATCH v14 05/11] io_uring/zcrx: dma-map area for the device

[David Wei]

From: Pavel Begunkov <asml.silence@gmail.com>

Setup DMA mappings for the area into which we intend to receive data
later on. We know the device we want to attach to even before we get a
page pool and can pre-map in advance. All net_iov are synchronised for
device when allocated, see page_pool_mp_return_in_cache().

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++-
 io_uring/zcrx.h |  1 +
 2 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index f9e924cfa829..9d14fdf7a568 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/dma-map-ops.h>
 #include <linux/mm.h>
 #include <linux/nospec.h>
 #include <linux/io_uring.h>
@@ -21,6 +22,73 @@
 #include "zcrx.h"
 #include "rsrc.h"
 
+#define IO_DMA_ATTR (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING)
+
+static void __io_zcrx_unmap_area(struct io_zcrx_ifq *ifq,
+				 struct io_zcrx_area *area, int nr_mapped)
+{
+	int i;
+
+	for (i = 0; i < nr_mapped; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+		dma_addr_t dma;
+
+		dma = page_pool_get_dma_addr_netmem(net_iov_to_netmem(niov));
+		dma_unmap_page_attrs(ifq->dev, dma, PAGE_SIZE,
+				     DMA_FROM_DEVICE, IO_DMA_ATTR);
+		net_mp_niov_set_dma_addr(niov, 0);
+	}
+}
+
+static void io_zcrx_unmap_area(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
+{
+	if (area->is_mapped)
+		__io_zcrx_unmap_area(ifq, area, area->nia.num_niovs);
+}
+
+static int io_zcrx_map_area(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
+{
+	int i;
+
+	for (i = 0; i < area->nia.num_niovs; i++) {
+		struct net_iov *niov = &area->nia.niovs[i];
+		dma_addr_t dma;
+
+		dma = dma_map_page_attrs(ifq->dev, area->pages[i], 0, PAGE_SIZE,
+					 DMA_FROM_DEVICE, IO_DMA_ATTR);
+		if (dma_mapping_error(ifq->dev, dma))
+			break;
+		if (net_mp_niov_set_dma_addr(niov, dma)) {
+			dma_unmap_page_attrs(ifq->dev, dma, PAGE_SIZE,
+					     DMA_FROM_DEVICE, IO_DMA_ATTR);
+			break;
+		}
+	}
+
+	if (i != area->nia.num_niovs) {
+		__io_zcrx_unmap_area(ifq, area, i);
+		return -EINVAL;
+	}
+
+	area->is_mapped = true;
+	return 0;
+}
+
+static void io_zcrx_sync_for_device(const struct page_pool *pool,
+				    struct net_iov *niov)
+{
+#if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
+	dma_addr_t dma_addr;
+
+	if (!dma_dev_need_sync(pool->p.dev))
+		return;
+
+	dma_addr = page_pool_get_dma_addr_netmem(net_iov_to_netmem(niov));
+	__dma_sync_single_for_device(pool->p.dev, dma_addr + pool->p.offset,
+				     PAGE_SIZE, pool->p.dma_dir);
+#endif
+}
+
 #define IO_RQ_MAX_ENTRIES		32768
 
 __maybe_unused
@@ -83,6 +151,8 @@ static void io_free_rbuf_ring(struct io_zcrx_ifq *ifq)
 
 static void io_zcrx_free_area(struct io_zcrx_area *area)
 {
+	io_zcrx_unmap_area(area->ifq, area);
+
 	kvfree(area->freelist);
 	kvfree(area->nia.niovs);
 	kvfree(area->user_refs);
@@ -272,6 +342,10 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		return -EOPNOTSUPP;
 	get_device(ifq->dev);
 
+	ret = io_zcrx_map_area(ifq, ifq->area);
+	if (ret)
+		goto err;
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);
@@ -422,6 +496,7 @@ static void io_zcrx_ring_refill(struct page_pool *pp,
 			continue;
 		}
 
+		io_zcrx_sync_for_device(pp, niov);
 		net_mp_netmem_place_in_cache(pp, netmem);
 	} while (--entries);
 
@@ -439,6 +514,7 @@ static void io_zcrx_refill_slow(struct page_pool *pp, struct io_zcrx_ifq *ifq)
 		netmem_ref netmem = net_iov_to_netmem(niov);
 
 		net_mp_niov_set_page_pool(pp, niov);
+		io_zcrx_sync_for_device(pp, niov);
 		net_mp_netmem_place_in_cache(pp, netmem);
 	}
 	spin_unlock_bh(&area->freelist_lock);
@@ -482,10 +558,14 @@ static int io_pp_zc_init(struct page_pool *pp)
 
 	if (WARN_ON_ONCE(!ifq))
 		return -EINVAL;
-	if (pp->dma_map)
+	if (WARN_ON_ONCE(ifq->dev != pp->p.dev))
+		return -EINVAL;
+	if (WARN_ON_ONCE(!pp->dma_map))
 		return -EOPNOTSUPP;
 	if (pp->p.order != 0)
 		return -EOPNOTSUPP;
+	if (pp->p.dma_dir != DMA_FROM_DEVICE)
+		return -EOPNOTSUPP;
 
 	percpu_ref_get(&ifq->ctx->refs);
 	return 0;
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 6c808240ac91..1b6363591f72 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -11,6 +11,7 @@ struct io_zcrx_area {
 	struct io_zcrx_ifq	*ifq;
 	atomic_t		*user_refs;
 
+	bool			is_mapped;
 	u16			area_id;
 	struct page		**pages;
 
-- 
2.43.5

[PATCH v14 06/11] io_uring/zcrx: add io_recvzc request

[David Wei]

Add io_uring opcode OP_RECV_ZC for doing zero copy reads out of a
socket. Only the connection should be land on the specific rx queue set
up for zero copy, and the socket must be handled by the io_uring
instance that the rx queue was registered for zero copy with. That's
because neither net_iovs / buffers from our queue can be read by outside
applications, nor zero copy is possible if traffic for the zero copy
connection goes to another queue. This coordination is outside of the
scope of this patch series. Also, any traffic directed to the zero copy
enabled queue is immediately visible to the application, which is why
CAP_NET_ADMIN is required at the registration step.

Of course, no data is actually read out of the socket, it has already
been copied by the netdev into userspace memory via DMA. OP_RECV_ZC
reads skbs out of the socket and checks that its frags are indeed
net_iovs that belong to io_uring. A cqe is queued for each one of these
frags.

Recall that each cqe is a big cqe, with the top half being an
io_uring_zcrx_cqe. The cqe res field contains the len or error. The
lower IORING_ZCRX_AREA_SHIFT bits of the struct io_uring_zcrx_cqe::off
field contain the offset relative to the start of the zero copy area.
The upper part of the off field is trivially zero, and will be used
to carry the area id.

For now, there is no limit as to how much work each OP_RECV_ZC request
does. It will attempt to drain a socket of all available data. This
request always operates in multishot mode.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 include/uapi/linux/io_uring.h |   2 +
 io_uring/io_uring.h           |  10 ++
 io_uring/net.c                |  72 +++++++++++++
 io_uring/opdef.c              |  16 +++
 io_uring/zcrx.c               | 190 +++++++++++++++++++++++++++++++++-
 io_uring/zcrx.h               |  13 +++
 6 files changed, 302 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 44844707d327..05d6255b0f6a 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -87,6 +87,7 @@ struct io_uring_sqe {
 	union {
 		__s32	splice_fd_in;
 		__u32	file_index;
+		__u32	zcrx_ifq_idx;
 		__u32	optlen;
 		struct {
 			__u16	addr_len;
@@ -278,6 +279,7 @@ enum io_uring_op {
 	IORING_OP_FTRUNCATE,
 	IORING_OP_BIND,
 	IORING_OP_LISTEN,
+	IORING_OP_RECV_ZC,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 85bc8f76ca19..fd0dbe7b0c9a 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -185,6 +185,16 @@ static inline bool io_get_cqe(struct io_ring_ctx *ctx, struct io_uring_cqe **ret
 	return io_get_cqe_overflow(ctx, ret, false);
 }
 
+static inline bool io_defer_get_uncommited_cqe(struct io_ring_ctx *ctx,
+					       struct io_uring_cqe **cqe_ret)
+{
+	io_lockdep_assert_cq_locked(ctx);
+
+	ctx->cq_extra++;
+	ctx->submit_state.cq_flush = true;
+	return io_get_cqe(ctx, cqe_ret);
+}
+
 static __always_inline bool io_fill_cqe_req(struct io_ring_ctx *ctx,
 					    struct io_kiocb *req)
 {
diff --git a/io_uring/net.c b/io_uring/net.c
index 10344b3a6d89..260eb73a5854 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -16,6 +16,7 @@
 #include "net.h"
 #include "notif.h"
 #include "rsrc.h"
+#include "zcrx.h"
 
 #if defined(CONFIG_NET)
 struct io_shutdown {
@@ -89,6 +90,13 @@ struct io_sr_msg {
  */
 #define MULTISHOT_MAX_RETRY	32
 
+struct io_recvzc {
+	struct file			*file;
+	unsigned			msg_flags;
+	u16				flags;
+	struct io_zcrx_ifq		*ifq;
+};
+
 int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_shutdown *shutdown = io_kiocb_to_cmd(req, struct io_shutdown);
@@ -1227,6 +1235,70 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	return ret;
 }
 
+int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_recvzc *zc = io_kiocb_to_cmd(req, struct io_recvzc);
+	unsigned ifq_idx;
+
+	if (unlikely(sqe->file_index || sqe->addr2 || sqe->addr ||
+		     sqe->len || sqe->addr3))
+		return -EINVAL;
+
+	ifq_idx = READ_ONCE(sqe->zcrx_ifq_idx);
+	if (ifq_idx != 0)
+		return -EINVAL;
+	zc->ifq = req->ctx->ifq;
+	if (!zc->ifq)
+		return -EINVAL;
+
+	zc->flags = READ_ONCE(sqe->ioprio);
+	zc->msg_flags = READ_ONCE(sqe->msg_flags);
+	if (zc->msg_flags)
+		return -EINVAL;
+	if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST | IORING_RECV_MULTISHOT))
+		return -EINVAL;
+	/* multishot required */
+	if (!(zc->flags & IORING_RECV_MULTISHOT))
+		return -EINVAL;
+	/* All data completions are posted as aux CQEs. */
+	req->flags |= REQ_F_APOLL_MULTISHOT;
+
+	return 0;
+}
+
+int io_recvzc(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_recvzc *zc = io_kiocb_to_cmd(req, struct io_recvzc);
+	struct socket *sock;
+	int ret;
+
+	if (!(req->flags & REQ_F_POLLED) &&
+	    (zc->flags & IORING_RECVSEND_POLL_FIRST))
+		return -EAGAIN;
+
+	sock = sock_from_file(req->file);
+	if (unlikely(!sock))
+		return -ENOTSOCK;
+
+	ret = io_zcrx_recv(req, zc->ifq, sock, zc->msg_flags | MSG_DONTWAIT,
+			   issue_flags);
+	if (unlikely(ret <= 0) && ret != -EAGAIN) {
+		if (ret == -ERESTARTSYS)
+			ret = -EINTR;
+
+		req_set_fail(req);
+		io_req_set_res(req, ret, 0);
+
+		if (issue_flags & IO_URING_F_MULTISHOT)
+			return IOU_STOP_MULTISHOT;
+		return IOU_OK;
+	}
+
+	if (issue_flags & IO_URING_F_MULTISHOT)
+		return IOU_ISSUE_SKIP_COMPLETE;
+	return -EAGAIN;
+}
+
 void io_send_zc_cleanup(struct io_kiocb *req)
 {
 	struct io_sr_msg *zc = io_kiocb_to_cmd(req, struct io_sr_msg);
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index e8baef4e5146..89f50ecadeaf 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -37,6 +37,7 @@
 #include "waitid.h"
 #include "futex.h"
 #include "truncate.h"
+#include "zcrx.h"
 
 static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
 {
@@ -514,6 +515,18 @@ const struct io_issue_def io_issue_defs[] = {
 		.async_size		= sizeof(struct io_async_msghdr),
 #else
 		.prep			= io_eopnotsupp_prep,
+#endif
+	},
+	[IORING_OP_RECV_ZC] = {
+		.needs_file		= 1,
+		.unbound_nonreg_file	= 1,
+		.pollin			= 1,
+		.ioprio			= 1,
+#if defined(CONFIG_NET)
+		.prep			= io_recvzc_prep,
+		.issue			= io_recvzc,
+#else
+		.prep			= io_eopnotsupp_prep,
 #endif
 	},
 };
@@ -745,6 +758,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_LISTEN] = {
 		.name			= "LISTEN",
 	},
+	[IORING_OP_RECV_ZC] = {
+		.name			= "RECV_ZC",
+	},
 };
 
 const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 9d14fdf7a568..8833879d94ba 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -13,6 +13,8 @@
 #include <net/netlink.h>
 
 #include <trace/events/page_pool.h>
+#include <net/tcp.h>
+#include <net/rps.h>
 
 #include <uapi/linux/io_uring.h>
 
@@ -91,7 +93,12 @@ static void io_zcrx_sync_for_device(const struct page_pool *pool,
 
 #define IO_RQ_MAX_ENTRIES		32768
 
-__maybe_unused
+struct io_zcrx_args {
+	struct io_kiocb		*req;
+	struct io_zcrx_ifq	*ifq;
+	struct socket		*sock;
+};
+
 static const struct memory_provider_ops io_uring_pp_zc_ops;
 
 static inline struct io_zcrx_area *io_zcrx_iov_to_area(const struct net_iov *niov)
@@ -118,6 +125,11 @@ static bool io_zcrx_put_niov_uref(struct net_iov *niov)
 	return true;
 }
 
+static void io_zcrx_get_niov_uref(struct net_iov *niov)
+{
+	atomic_inc(io_get_user_counter(niov));
+}
+
 static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 				 struct io_uring_zcrx_ifq_reg *reg,
 				 struct io_uring_region_desc *rd)
@@ -614,3 +626,179 @@ static const struct memory_provider_ops io_uring_pp_zc_ops = {
 	.nl_fill		= io_pp_nl_fill,
 	.uninstall		= io_pp_uninstall,
 };
+
+static bool io_zcrx_queue_cqe(struct io_kiocb *req, struct net_iov *niov,
+			      struct io_zcrx_ifq *ifq, int off, int len)
+{
+	struct io_uring_zcrx_cqe *rcqe;
+	struct io_zcrx_area *area;
+	struct io_uring_cqe *cqe;
+	u64 offset;
+
+	if (!io_defer_get_uncommited_cqe(req->ctx, &cqe))
+		return false;
+
+	cqe->user_data = req->cqe.user_data;
+	cqe->res = len;
+	cqe->flags = IORING_CQE_F_MORE;
+
+	area = io_zcrx_iov_to_area(niov);
+	offset = off + (net_iov_idx(niov) << PAGE_SHIFT);
+	rcqe = (struct io_uring_zcrx_cqe *)(cqe + 1);
+	rcqe->off = offset + ((u64)area->area_id << IORING_ZCRX_AREA_SHIFT);
+	rcqe->__pad = 0;
+	return true;
+}
+
+static int io_zcrx_recv_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+			     const skb_frag_t *frag, int off, int len)
+{
+	struct net_iov *niov;
+
+	if (unlikely(!skb_frag_is_net_iov(frag)))
+		return -EOPNOTSUPP;
+
+	niov = netmem_to_net_iov(frag->netmem);
+	if (niov->pp->mp_ops != &io_uring_pp_zc_ops ||
+	    niov->pp->mp_priv != ifq)
+		return -EFAULT;
+
+	if (!io_zcrx_queue_cqe(req, niov, ifq, off + skb_frag_off(frag), len))
+		return -ENOSPC;
+
+	/*
+	 * Prevent it from being recycled while user is accessing it.
+	 * It has to be done before grabbing a user reference.
+	 */
+	page_pool_ref_netmem(net_iov_to_netmem(niov));
+	io_zcrx_get_niov_uref(niov);
+	return len;
+}
+
+static int
+io_zcrx_recv_skb(read_descriptor_t *desc, struct sk_buff *skb,
+		 unsigned int offset, size_t len)
+{
+	struct io_zcrx_args *args = desc->arg.data;
+	struct io_zcrx_ifq *ifq = args->ifq;
+	struct io_kiocb *req = args->req;
+	struct sk_buff *frag_iter;
+	unsigned start, start_off;
+	int i, copy, end, off;
+	int ret = 0;
+
+	start = skb_headlen(skb);
+	start_off = offset;
+
+	if (offset < start)
+		return -EOPNOTSUPP;
+
+	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+		const skb_frag_t *frag;
+
+		if (WARN_ON(start > offset + len))
+			return -EFAULT;
+
+		frag = &skb_shinfo(skb)->frags[i];
+		end = start + skb_frag_size(frag);
+
+		if (offset < end) {
+			copy = end - offset;
+			if (copy > len)
+				copy = len;
+
+			off = offset - start;
+			ret = io_zcrx_recv_frag(req, ifq, frag, off, copy);
+			if (ret < 0)
+				goto out;
+
+			offset += ret;
+			len -= ret;
+			if (len == 0 || ret != copy)
+				goto out;
+		}
+		start = end;
+	}
+
+	skb_walk_frags(skb, frag_iter) {
+		if (WARN_ON(start > offset + len))
+			return -EFAULT;
+
+		end = start + frag_iter->len;
+		if (offset < end) {
+			copy = end - offset;
+			if (copy > len)
+				copy = len;
+
+			off = offset - start;
+			ret = io_zcrx_recv_skb(desc, frag_iter, off, copy);
+			if (ret < 0)
+				goto out;
+
+			offset += ret;
+			len -= ret;
+			if (len == 0 || ret != copy)
+				goto out;
+		}
+		start = end;
+	}
+
+out:
+	if (offset == start_off)
+		return ret;
+	return offset - start_off;
+}
+
+static int io_zcrx_tcp_recvmsg(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+				struct sock *sk, int flags,
+				unsigned issue_flags)
+{
+	struct io_zcrx_args args = {
+		.req = req,
+		.ifq = ifq,
+		.sock = sk->sk_socket,
+	};
+	read_descriptor_t rd_desc = {
+		.count = 1,
+		.arg.data = &args,
+	};
+	int ret;
+
+	lock_sock(sk);
+	ret = tcp_read_sock(sk, &rd_desc, io_zcrx_recv_skb);
+	if (ret <= 0) {
+		if (ret < 0 || sock_flag(sk, SOCK_DONE))
+			goto out;
+		if (sk->sk_err)
+			ret = sock_error(sk);
+		else if (sk->sk_shutdown & RCV_SHUTDOWN)
+			goto out;
+		else if (sk->sk_state == TCP_CLOSE)
+			ret = -ENOTCONN;
+		else
+			ret = -EAGAIN;
+	} else if (sock_flag(sk, SOCK_DONE)) {
+		/* Make it to retry until it finally gets 0. */
+		if (issue_flags & IO_URING_F_MULTISHOT)
+			ret = IOU_REQUEUE;
+		else
+			ret = -EAGAIN;
+	}
+out:
+	release_sock(sk);
+	return ret;
+}
+
+int io_zcrx_recv(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+		 struct socket *sock, unsigned int flags,
+		 unsigned issue_flags)
+{
+	struct sock *sk = sock->sk;
+	const struct proto *prot = READ_ONCE(sk->sk_prot);
+
+	if (prot->recvmsg != tcp_recvmsg)
+		return -EPROTONOSUPPORT;
+
+	sock_rps_record_flow(sk);
+	return io_zcrx_tcp_recvmsg(req, ifq, sk, flags, issue_flags);
+}
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index 1b6363591f72..a16bdd921f03 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -3,6 +3,7 @@
 #define IOU_ZC_RX_H
 
 #include <linux/io_uring_types.h>
+#include <linux/socket.h>
 #include <net/page_pool/types.h>
 #include <net/net_trackers.h>
 
@@ -43,6 +44,9 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 			 struct io_uring_zcrx_ifq_reg __user *arg);
 void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx);
 void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx);
+int io_zcrx_recv(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+		 struct socket *sock, unsigned int flags,
+		 unsigned issue_flags);
 #else
 static inline int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 					struct io_uring_zcrx_ifq_reg __user *arg)
@@ -55,6 +59,15 @@ static inline void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
 static inline void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 {
 }
+static inline int io_zcrx_recv(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+			       struct socket *sock, unsigned int flags,
+			       unsigned issue_flags)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
+int io_recvzc(struct io_kiocb *req, unsigned int issue_flags);
+int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+
 #endif
-- 
2.43.5

[PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx queue

[David Wei]

Set the page pool memory provider for the rx queue configured for zero
copy to io_uring. Then the rx queue is reset using
netdev_rx_queue_restart() and netdev core + page pool will take care of
filling the rx queue from the io_uring zero copy memory provider.

For now, there is only one ifq so its destruction happens implicitly
during io_uring cleanup.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 41 insertions(+), 8 deletions(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 8833879d94ba..7d24fc98b306 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -11,11 +11,12 @@
 #include <net/page_pool/helpers.h>
 #include <net/page_pool/memory_provider.h>
 #include <net/netlink.h>
-
-#include <trace/events/page_pool.h>
+#include <net/netdev_rx_queue.h>
 #include <net/tcp.h>
 #include <net/rps.h>
 
+#include <trace/events/page_pool.h>
+
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
@@ -275,8 +276,34 @@ static void io_zcrx_drop_netdev(struct io_zcrx_ifq *ifq)
 	spin_unlock(&ifq->lock);
 }
 
+static void io_close_queue(struct io_zcrx_ifq *ifq)
+{
+	struct net_device *netdev;
+	netdevice_tracker netdev_tracker;
+	struct pp_memory_provider_params p = {
+		.mp_ops = &io_uring_pp_zc_ops,
+		.mp_priv = ifq,
+	};
+
+	if (ifq->if_rxq == -1)
+		return;
+
+	spin_lock(&ifq->lock);
+	netdev = ifq->netdev;
+	netdev_tracker = ifq->netdev_tracker;
+	ifq->netdev = NULL;
+	spin_unlock(&ifq->lock);
+
+	if (netdev) {
+		net_mp_close_rxq(netdev, ifq->if_rxq, &p);
+		netdev_put(netdev, &netdev_tracker);
+	}
+	ifq->if_rxq = -1;
+}
+
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	io_close_queue(ifq);
 	io_zcrx_drop_netdev(ifq);
 
 	if (ifq->area)
@@ -291,6 +318,7 @@ static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 			  struct io_uring_zcrx_ifq_reg __user *arg)
 {
+	struct pp_memory_provider_params mp_param = {};
 	struct io_uring_zcrx_area_reg area;
 	struct io_uring_zcrx_ifq_reg reg;
 	struct io_uring_region_desc rd;
@@ -341,7 +369,6 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		goto err;
 
 	ifq->rq_entries = reg.rq_entries;
-	ifq->if_rxq = reg.if_rxq;
 
 	ret = -ENODEV;
 	ifq->netdev = netdev_get_by_index(current->nsproxy->net_ns, reg.if_idx,
@@ -358,16 +385,20 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	if (ret)
 		goto err;
 
+	mp_param.mp_ops = &io_uring_pp_zc_ops;
+	mp_param.mp_priv = ifq;
+	ret = net_mp_open_rxq(ifq->netdev, reg.if_rxq, &mp_param);
+	if (ret)
+		goto err;
+	ifq->if_rxq = reg.if_rxq;
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);
 
 	if (copy_to_user(arg, &reg, sizeof(reg)) ||
-	    copy_to_user(u64_to_user_ptr(reg.region_ptr), &rd, sizeof(rd))) {
-		ret = -EFAULT;
-		goto err;
-	}
-	if (copy_to_user(u64_to_user_ptr(reg.area_ptr), &area, sizeof(area))) {
+	    copy_to_user(u64_to_user_ptr(reg.region_ptr), &rd, sizeof(rd)) ||
+	    copy_to_user(u64_to_user_ptr(reg.area_ptr), &area, sizeof(area))) {
 		ret = -EFAULT;
 		goto err;
 	}
@@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 
 	if (ctx->ifq)
 		io_zcrx_scrub(ctx->ifq);
+
+	io_close_queue(ctx->ifq);
 }
 
 static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)
-- 
2.43.5

[PATCH v14 08/11] io_uring/zcrx: throttle receive requests

[David Wei]

From: Pavel Begunkov <asml.silence@gmail.com>

io_zc_rx_tcp_recvmsg() continues until it fails or there is nothing to
receive. If the other side sends fast enough, we might get stuck in
io_zc_rx_tcp_recvmsg() producing more and more CQEs but not letting the
user to handle them leading to unbound latencies.

Break out of it based on an arbitrarily chosen limit, the upper layer
will either return to userspace or requeue the request.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/net.c  | 2 ++
 io_uring/zcrx.c | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/io_uring/net.c b/io_uring/net.c
index 260eb73a5854..000dc70d08d0 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1285,6 +1285,8 @@ int io_recvzc(struct io_kiocb *req, unsigned int issue_flags)
 	if (unlikely(ret <= 0) && ret != -EAGAIN) {
 		if (ret == -ERESTARTSYS)
 			ret = -EINTR;
+		if (ret == IOU_REQUEUE)
+			return IOU_REQUEUE;
 
 		req_set_fail(req);
 		io_req_set_res(req, ret, 0);
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 7d24fc98b306..7e0cba1e0f39 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -94,10 +94,13 @@ static void io_zcrx_sync_for_device(const struct page_pool *pool,
 
 #define IO_RQ_MAX_ENTRIES		32768
 
+#define IO_SKBS_PER_CALL_LIMIT	20
+
 struct io_zcrx_args {
 	struct io_kiocb		*req;
 	struct io_zcrx_ifq	*ifq;
 	struct socket		*sock;
+	unsigned		nr_skbs;
 };
 
 static const struct memory_provider_ops io_uring_pp_zc_ops;
@@ -720,6 +723,9 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct sk_buff *skb,
 	int i, copy, end, off;
 	int ret = 0;
 
+	if (unlikely(args->nr_skbs++ > IO_SKBS_PER_CALL_LIMIT))
+		return -EAGAIN;
+
 	start = skb_headlen(skb);
 	start_off = offset;
 
@@ -810,6 +816,9 @@ static int io_zcrx_tcp_recvmsg(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
 			ret = -ENOTCONN;
 		else
 			ret = -EAGAIN;
+	} else if (unlikely(args.nr_skbs > IO_SKBS_PER_CALL_LIMIT) &&
+		   (issue_flags & IO_URING_F_MULTISHOT)) {
+		ret = IOU_REQUEUE;
 	} else if (sock_flag(sk, SOCK_DONE)) {
 		/* Make it to retry until it finally gets 0. */
 		if (issue_flags & IO_URING_F_MULTISHOT)
-- 
2.43.5

[PATCH v14 09/11] io_uring/zcrx: add copy fallback

[David Wei]

From: Pavel Begunkov <asml.silence@gmail.com>

There are scenarios in which the zerocopy path can get a kernel buffer
instead of a net_iov and needs to copy it to the user, whether it is
because of mis-steering or simply getting an skb with the linear part.
In this case, grab a net_iov, copy into it and return it to the user as
normally.

At the moment the user doesn't get any indication whether there was a
copy or not, which is left for follow up work.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 120 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 114 insertions(+), 6 deletions(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 7e0cba1e0f39..026efb8dd381 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -7,6 +7,7 @@
 #include <linux/io_uring.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
+#include <linux/skbuff_ref.h>
 
 #include <net/page_pool/helpers.h>
 #include <net/page_pool/memory_provider.h>
@@ -134,6 +135,13 @@ static void io_zcrx_get_niov_uref(struct net_iov *niov)
 	atomic_inc(io_get_user_counter(niov));
 }
 
+static inline struct page *io_zcrx_iov_page(const struct net_iov *niov)
+{
+	struct io_zcrx_area *area = io_zcrx_iov_to_area(niov);
+
+	return area->pages[net_iov_idx(niov)];
+}
+
 static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 				 struct io_uring_zcrx_ifq_reg *reg,
 				 struct io_uring_region_desc *rd)
@@ -448,6 +456,11 @@ static void io_zcrx_return_niov(struct net_iov *niov)
 {
 	netmem_ref netmem = net_iov_to_netmem(niov);
 
+	if (!niov->pp) {
+		/* copy fallback allocated niovs */
+		io_zcrx_return_niov_freelist(niov);
+		return;
+	}
 	page_pool_put_unrefed_netmem(niov->pp, netmem, -1, false);
 }
 
@@ -686,13 +699,93 @@ static bool io_zcrx_queue_cqe(struct io_kiocb *req, struct net_iov *niov,
 	return true;
 }
 
+static struct net_iov *io_zcrx_alloc_fallback(struct io_zcrx_area *area)
+{
+	struct net_iov *niov = NULL;
+
+	spin_lock_bh(&area->freelist_lock);
+	if (area->free_count)
+		niov = __io_zcrx_get_free_niov(area);
+	spin_unlock_bh(&area->freelist_lock);
+
+	if (niov)
+		page_pool_fragment_netmem(net_iov_to_netmem(niov), 1);
+	return niov;
+}
+
+static ssize_t io_zcrx_copy_chunk(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+				  void *src_base, struct page *src_page,
+				  unsigned int src_offset, size_t len)
+{
+	struct io_zcrx_area *area = ifq->area;
+	size_t copied = 0;
+	int ret = 0;
+
+	while (len) {
+		size_t copy_size = min_t(size_t, PAGE_SIZE, len);
+		const int dst_off = 0;
+		struct net_iov *niov;
+		struct page *dst_page;
+		void *dst_addr;
+
+		niov = io_zcrx_alloc_fallback(area);
+		if (!niov) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		dst_page = io_zcrx_iov_page(niov);
+		dst_addr = kmap_local_page(dst_page);
+		if (src_page)
+			src_base = kmap_local_page(src_page);
+
+		memcpy(dst_addr, src_base + src_offset, copy_size);
+
+		if (src_page)
+			kunmap_local(src_base);
+		kunmap_local(dst_addr);
+
+		if (!io_zcrx_queue_cqe(req, niov, ifq, dst_off, copy_size)) {
+			io_zcrx_return_niov(niov);
+			ret = -ENOSPC;
+			break;
+		}
+
+		io_zcrx_get_niov_uref(niov);
+		src_offset += copy_size;
+		len -= copy_size;
+		copied += copy_size;
+	}
+
+	return copied ? copied : ret;
+}
+
+static int io_zcrx_copy_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
+			     const skb_frag_t *frag, int off, int len)
+{
+	struct page *page = skb_frag_page(frag);
+	u32 p_off, p_len, t, copied = 0;
+	int ret = 0;
+
+	off += skb_frag_off(frag);
+
+	skb_frag_foreach_page(frag, off, len,
+			      page, p_off, p_len, t) {
+		ret = io_zcrx_copy_chunk(req, ifq, NULL, page, p_off, p_len);
+		if (ret < 0)
+			return copied ? copied : ret;
+		copied += ret;
+	}
+	return copied;
+}
+
 static int io_zcrx_recv_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
 			     const skb_frag_t *frag, int off, int len)
 {
 	struct net_iov *niov;
 
 	if (unlikely(!skb_frag_is_net_iov(frag)))
-		return -EOPNOTSUPP;
+		return io_zcrx_copy_frag(req, ifq, frag, off, len);
 
 	niov = netmem_to_net_iov(frag->netmem);
 	if (niov->pp->mp_ops != &io_uring_pp_zc_ops ||
@@ -719,18 +812,33 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct sk_buff *skb,
 	struct io_zcrx_ifq *ifq = args->ifq;
 	struct io_kiocb *req = args->req;
 	struct sk_buff *frag_iter;
-	unsigned start, start_off;
+	unsigned start, start_off = offset;
 	int i, copy, end, off;
 	int ret = 0;
 
 	if (unlikely(args->nr_skbs++ > IO_SKBS_PER_CALL_LIMIT))
 		return -EAGAIN;
 
-	start = skb_headlen(skb);
-	start_off = offset;
+	if (unlikely(offset < skb_headlen(skb))) {
+		ssize_t copied;
+		size_t to_copy;
 
-	if (offset < start)
-		return -EOPNOTSUPP;
+		to_copy = min_t(size_t, skb_headlen(skb) - offset, len);
+		copied = io_zcrx_copy_chunk(req, ifq, skb->data, NULL,
+					    offset, to_copy);
+		if (copied < 0) {
+			ret = copied;
+			goto out;
+		}
+		offset += copied;
+		len -= copied;
+		if (!len)
+			goto out;
+		if (offset != skb_headlen(skb))
+			goto out;
+	}
+
+	start = skb_headlen(skb);
 
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		const skb_frag_t *frag;
-- 
2.43.5

[PATCH v14 10/11] net: add documentation for io_uring zcrx

[David Wei]

Add documentation for io_uring zero copy Rx that explains requirements
and the user API.

Signed-off-by: David Wei <dw@davidwei.uk>
---
 Documentation/networking/index.rst    |   1 +
 Documentation/networking/iou-zcrx.rst | 202 ++++++++++++++++++++++++++
 2 files changed, 203 insertions(+)
 create mode 100644 Documentation/networking/iou-zcrx.rst

diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst
index 058193ed2eeb..c64133d309bf 100644
--- a/Documentation/networking/index.rst
+++ b/Documentation/networking/index.rst
@@ -63,6 +63,7 @@ Contents:
    gtp
    ila
    ioam6-sysctl
+   iou-zcrx
    ip_dynaddr
    ipsec
    ip-sysctl
diff --git a/Documentation/networking/iou-zcrx.rst b/Documentation/networking/iou-zcrx.rst
new file mode 100644
index 000000000000..0127319b30bb
--- /dev/null
+++ b/Documentation/networking/iou-zcrx.rst
@@ -0,0 +1,202 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+io_uring zero copy Rx
+=====================
+
+Introduction
+============
+
+io_uring zero copy Rx (ZC Rx) is a feature that removes kernel-to-user copy on
+the network receive path, allowing packet data to be received directly into
+userspace memory. This feature is different to TCP_ZEROCOPY_RECEIVE in that
+there are no strict alignment requirements and no need to mmap()/munmap().
+Compared to kernel bypass solutions such as e.g. DPDK, the packet headers are
+processed by the kernel TCP stack as normal.
+
+NIC HW Requirements
+===================
+
+Several NIC HW features are required for io_uring ZC Rx to work. For now the
+kernel API does not configure the NIC and it must be done by the user.
+
+Header/data split
+-----------------
+
+Required to split packets at the L4 boundary into a header and a payload.
+Headers are received into kernel memory as normal and processed by the TCP
+stack as normal. Payloads are received into userspace memory directly.
+
+Flow steering
+-------------
+
+Specific HW Rx queues are configured for this feature, but modern NICs
+typically distribute flows across all HW Rx queues. Flow steering is required
+to ensure that only desired flows are directed towards HW queues that are
+configured for io_uring ZC Rx.
+
+RSS
+---
+
+In addition to flow steering above, RSS is required to steer all other non-zero
+copy flows away from queues that are configured for io_uring ZC Rx.
+
+Usage
+=====
+
+Setup NIC
+---------
+
+Must be done out of band for now.
+
+Ensure there are at least two queues::
+
+  ethtool -L eth0 combined 2
+
+Enable header/data split::
+
+  ethtool -G eth0 tcp-data-split on
+
+Carve out half of the HW Rx queues for zero copy using RSS::
+
+  ethtool -X eth0 equal 1
+
+Set up flow steering, bearing in mind that queues are 0-indexed::
+
+  ethtool -N eth0 flow-type tcp6 ... action 1
+
+Setup io_uring
+--------------
+
+This section describes the low level io_uring kernel API. Please refer to
+liburing documentation for how to use the higher level API.
+
+Create an io_uring instance with the following required setup flags::
+
+  IORING_SETUP_SINGLE_ISSUER
+  IORING_SETUP_DEFER_TASKRUN
+  IORING_SETUP_CQE32
+
+Create memory area
+------------------
+
+Allocate userspace memory area for receiving zero copy data::
+
+  void *area_ptr = mmap(NULL, area_size,
+                        PROT_READ | PROT_WRITE,
+                        MAP_ANONYMOUS | MAP_PRIVATE,
+                        0, 0);
+
+Create refill ring
+------------------
+
+Allocate memory for a shared ringbuf used for returning consumed buffers::
+
+  void *ring_ptr = mmap(NULL, ring_size,
+                        PROT_READ | PROT_WRITE,
+                        MAP_ANONYMOUS | MAP_PRIVATE,
+                        0, 0);
+
+This refill ring consists of some space for the header, followed by an array of
+``struct io_uring_zcrx_rqe``::
+
+  size_t rq_entries = 4096;
+  size_t ring_size = rq_entries * sizeof(struct io_uring_zcrx_rqe) + PAGE_SIZE;
+  /* align to page size */
+  ring_size = (ring_size + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
+
+Register ZC Rx
+--------------
+
+Fill in registration structs::
+
+  struct io_uring_zcrx_area_reg area_reg = {
+    .addr = (__u64)(unsigned long)area_ptr,
+    .len = area_size,
+    .flags = 0,
+  };
+
+  struct io_uring_region_desc region_reg = {
+    .user_addr = (__u64)(unsigned long)ring_ptr,
+    .size = ring_size,
+    .flags = IORING_MEM_REGION_TYPE_USER,
+  };
+
+  struct io_uring_zcrx_ifq_reg reg = {
+    .if_idx = if_nametoindex("eth0"),
+    /* this is the HW queue with desired flow steered into it */
+    .if_rxq = 1,
+    .rq_entries = rq_entries,
+    .area_ptr = (__u64)(unsigned long)&area_reg,
+    .region_ptr = (__u64)(unsigned long)&region_reg,
+  };
+
+Register with kernel::
+
+  io_uring_register_ifq(ring, &reg);
+
+Map refill ring
+---------------
+
+The kernel fills in fields for the refill ring in the registration ``struct
+io_uring_zcrx_ifq_reg``. Map it into userspace::
+
+  struct io_uring_zcrx_rq refill_ring;
+
+  refill_ring.khead = (unsigned *)((char *)ring_ptr + reg.offsets.head);
+  refill_ring.khead = (unsigned *)((char *)ring_ptr + reg.offsets.tail);
+  refill_ring.rqes =
+    (struct io_uring_zcrx_rqe *)((char *)ring_ptr + reg.offsets.rqes);
+  refill_ring.rq_tail = 0;
+  refill_ring.ring_ptr = ring_ptr;
+
+Receiving data
+--------------
+
+Prepare a zero copy recv request::
+
+  struct io_uring_sqe *sqe;
+
+  sqe = io_uring_get_sqe(ring);
+  io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, fd, NULL, 0, 0);
+  sqe->ioprio |= IORING_RECV_MULTISHOT;
+
+Now, submit and wait::
+
+  io_uring_submit_and_wait(ring, 1);
+
+Finally, process completions::
+
+  struct io_uring_cqe *cqe;
+  unsigned int count = 0;
+  unsigned int head;
+
+  io_uring_for_each_cqe(ring, head, cqe) {
+    struct io_uring_zcrx_cqe *rcqe = (struct io_uring_zcrx_cqe *)(cqe + 1);
+
+    unsigned long mask = (1ULL << IORING_ZCRX_AREA_SHIFT) - 1;
+    unsigned char *data = area_ptr + (rcqe->off & mask);
+    /* do something with the data */
+
+    count++;
+  }
+  io_uring_cq_advance(ring, count);
+
+Recycling buffers
+-----------------
+
+Return buffers back to the kernel to be used again::
+
+  struct io_uring_zcrx_rqe *rqe;
+  unsigned mask = refill_ring.ring_entries - 1;
+  rqe = &refill_ring.rqes[refill_ring.rq_tail & mask];
+
+  unsigned long area_offset = rcqe->off & ~IORING_ZCRX_AREA_MASK;
+  rqe->off = area_offset | area_reg.rq_area_token;
+  rqe->len = cqe->res;
+  IO_URING_WRITE_ONCE(*refill_ring.ktail, ++refill_ring.rq_tail);
+
+Testing
+=======
+
+See ``tools/testing/selftests/drivers/net/hw/iou-zcrx.c``
-- 
2.43.5

[PATCH v14 11/11] io_uring/zcrx: add selftest

[David Wei]

Add a selftest for io_uring zero copy Rx. This test cannot run locally
and requires a remote host to be configured in net.config. The remote
host must have hardware support for zero copy Rx as listed in the
documentation page. The test will restore the NIC config back to before
the test and is idempotent.

liburing is required to compile the test and be installed on the remote
host running the test.

Signed-off-by: David Wei <dw@davidwei.uk>
---
 .../selftests/drivers/net/hw/.gitignore       |   2 +
 .../testing/selftests/drivers/net/hw/Makefile |   5 +
 .../selftests/drivers/net/hw/iou-zcrx.c       | 426 ++++++++++++++++++
 .../selftests/drivers/net/hw/iou-zcrx.py      |  64 +++
 4 files changed, 497 insertions(+)
 create mode 100644 tools/testing/selftests/drivers/net/hw/iou-zcrx.c
 create mode 100755 tools/testing/selftests/drivers/net/hw/iou-zcrx.py

diff --git a/tools/testing/selftests/drivers/net/hw/.gitignore b/tools/testing/selftests/drivers/net/hw/.gitignore
index e9fe6ede681a..6942bf575497 100644
--- a/tools/testing/selftests/drivers/net/hw/.gitignore
+++ b/tools/testing/selftests/drivers/net/hw/.gitignore
@@ -1 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+iou-zcrx
 ncdevmem
diff --git a/tools/testing/selftests/drivers/net/hw/Makefile b/tools/testing/selftests/drivers/net/hw/Makefile
index 21ba64ce1e34..7efc47c89463 100644
--- a/tools/testing/selftests/drivers/net/hw/Makefile
+++ b/tools/testing/selftests/drivers/net/hw/Makefile
@@ -1,5 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0+ OR MIT
 
+TEST_GEN_FILES = iou-zcrx
+
 TEST_PROGS = \
 	csum.py \
 	devlink_port_split.py \
@@ -10,6 +12,7 @@ TEST_PROGS = \
 	ethtool_rmon.sh \
 	hw_stats_l3.sh \
 	hw_stats_l3_gre.sh \
+	iou-zcrx.py \
 	loopback.sh \
 	nic_link_layer.py \
 	nic_performance.py \
@@ -38,3 +41,5 @@ include ../../../lib.mk
 # YNL build
 YNL_GENS := ethtool netdev
 include ../../../net/ynl.mk
+
+$(OUTPUT)/iou-zcrx: LDLIBS += -luring
diff --git a/tools/testing/selftests/drivers/net/hw/iou-zcrx.c b/tools/testing/selftests/drivers/net/hw/iou-zcrx.c
new file mode 100644
index 000000000000..5d04dd55ae55
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/hw/iou-zcrx.c
@@ -0,0 +1,426 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <assert.h>
+#include <errno.h>
+#include <error.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+#include <linux/errqueue.h>
+#include <linux/if_packet.h>
+#include <linux/ipv6.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+#include <sys/epoll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+
+#include <liburing.h>
+
+#define PAGE_SIZE (4096)
+#define AREA_SIZE (8192 * PAGE_SIZE)
+#define SEND_SIZE (512 * 4096)
+#define min(a, b) \
+	({ \
+		typeof(a) _a = (a); \
+		typeof(b) _b = (b); \
+		_a < _b ? _a : _b; \
+	})
+#define min_t(t, a, b) \
+	({ \
+		t _ta = (a); \
+		t _tb = (b); \
+		min(_ta, _tb); \
+	})
+
+#define ALIGN_UP(v, align) (((v) + (align) - 1) & ~((align) - 1))
+
+static int cfg_server;
+static int cfg_client;
+static int cfg_port = 8000;
+static int cfg_payload_len;
+static const char *cfg_ifname;
+static int cfg_queue_id = -1;
+static struct sockaddr_in6 cfg_addr;
+
+static char payload[SEND_SIZE] __attribute__((aligned(PAGE_SIZE)));
+static void *area_ptr;
+static void *ring_ptr;
+static size_t ring_size;
+static struct io_uring_zcrx_rq rq_ring;
+static unsigned long area_token;
+static int connfd;
+static bool stop;
+static size_t received;
+
+static unsigned long gettimeofday_ms(void)
+{
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL);
+	return (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
+}
+
+static int parse_address(const char *str, int port, struct sockaddr_in6 *sin6)
+{
+	int ret;
+
+	sin6->sin6_family = AF_INET6;
+	sin6->sin6_port = htons(port);
+
+	ret = inet_pton(sin6->sin6_family, str, &sin6->sin6_addr);
+	if (ret != 1) {
+		/* fallback to plain IPv4 */
+		ret = inet_pton(AF_INET, str, &sin6->sin6_addr.s6_addr32[3]);
+		if (ret != 1)
+			return -1;
+
+		/* add ::ffff prefix */
+		sin6->sin6_addr.s6_addr32[0] = 0;
+		sin6->sin6_addr.s6_addr32[1] = 0;
+		sin6->sin6_addr.s6_addr16[4] = 0;
+		sin6->sin6_addr.s6_addr16[5] = 0xffff;
+	}
+
+	return 0;
+}
+
+static inline size_t get_refill_ring_size(unsigned int rq_entries)
+{
+	size_t size;
+
+	ring_size = rq_entries * sizeof(struct io_uring_zcrx_rqe);
+	/* add space for the header (head/tail/etc.) */
+	ring_size += PAGE_SIZE;
+	return ALIGN_UP(ring_size, 4096);
+}
+
+static void setup_zcrx(struct io_uring *ring)
+{
+	unsigned int ifindex;
+	unsigned int rq_entries = 4096;
+	int ret;
+
+	ifindex = if_nametoindex(cfg_ifname);
+	if (!ifindex)
+		error(1, 0, "bad interface name: %s", cfg_ifname);
+
+	area_ptr = mmap(NULL,
+			AREA_SIZE,
+			PROT_READ | PROT_WRITE,
+			MAP_ANONYMOUS | MAP_PRIVATE,
+			0,
+			0);
+	if (area_ptr == MAP_FAILED)
+		error(1, 0, "mmap(): zero copy area");
+
+	ring_size = get_refill_ring_size(rq_entries);
+	ring_ptr = mmap(NULL,
+			ring_size,
+			PROT_READ | PROT_WRITE,
+			MAP_ANONYMOUS | MAP_PRIVATE,
+			0,
+			0);
+
+	struct io_uring_region_desc region_reg = {
+		.size = ring_size,
+		.user_addr = (__u64)(unsigned long)ring_ptr,
+		.flags = IORING_MEM_REGION_TYPE_USER,
+	};
+
+	struct io_uring_zcrx_area_reg area_reg = {
+		.addr = (__u64)(unsigned long)area_ptr,
+		.len = AREA_SIZE,
+		.flags = 0,
+	};
+
+	struct io_uring_zcrx_ifq_reg reg = {
+		.if_idx = ifindex,
+		.if_rxq = cfg_queue_id,
+		.rq_entries = rq_entries,
+		.area_ptr = (__u64)(unsigned long)&area_reg,
+		.region_ptr = (__u64)(unsigned long)&region_reg,
+	};
+
+	ret = io_uring_register_ifq(ring, &reg);
+	if (ret)
+		error(1, 0, "io_uring_register_ifq(): %d", ret);
+
+	rq_ring.khead = (unsigned int *)((char *)ring_ptr + reg.offsets.head);
+	rq_ring.ktail = (unsigned int *)((char *)ring_ptr + reg.offsets.tail);
+	rq_ring.rqes = (struct io_uring_zcrx_rqe *)((char *)ring_ptr + reg.offsets.rqes);
+	rq_ring.rq_tail = 0;
+	rq_ring.ring_entries = reg.rq_entries;
+
+	area_token = area_reg.rq_area_token;
+}
+
+static void add_accept(struct io_uring *ring, int sockfd)
+{
+	struct io_uring_sqe *sqe;
+
+	sqe = io_uring_get_sqe(ring);
+
+	io_uring_prep_accept(sqe, sockfd, NULL, NULL, 0);
+	sqe->user_data = 1;
+}
+
+static void add_recvzc(struct io_uring *ring, int sockfd)
+{
+	struct io_uring_sqe *sqe;
+
+	sqe = io_uring_get_sqe(ring);
+
+	io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, sockfd, NULL, 0, 0);
+	sqe->ioprio |= IORING_RECV_MULTISHOT;
+	sqe->user_data = 2;
+}
+
+static void process_accept(struct io_uring *ring, struct io_uring_cqe *cqe)
+{
+	if (cqe->res < 0)
+		error(1, 0, "accept()");
+	if (connfd)
+		error(1, 0, "Unexpected second connection");
+
+	connfd = cqe->res;
+	add_recvzc(ring, connfd);
+}
+
+static void process_recvzc(struct io_uring *ring, struct io_uring_cqe *cqe)
+{
+	unsigned rq_mask = rq_ring.ring_entries - 1;
+	struct io_uring_zcrx_cqe *rcqe;
+	struct io_uring_zcrx_rqe *rqe;
+	struct io_uring_sqe *sqe;
+	uint64_t mask;
+	char *data;
+	ssize_t n;
+	int i;
+
+	if (cqe->res == 0 && cqe->flags == 0) {
+		stop = true;
+		return;
+	}
+
+	if (cqe->res < 0)
+		error(1, 0, "recvzc(): %d", cqe->res);
+
+	if (!(cqe->flags & IORING_CQE_F_MORE))
+		add_recvzc(ring, connfd);
+
+	rcqe = (struct io_uring_zcrx_cqe *)(cqe + 1);
+
+	n = cqe->res;
+	mask = (1ULL << IORING_ZCRX_AREA_SHIFT) - 1;
+	data = (char *)area_ptr + (rcqe->off & mask);
+
+	for (i = 0; i < n; i++) {
+		if (*(data + i) != payload[(received + i)])
+			error(1, 0, "payload mismatch");
+	}
+	received += n;
+
+	rqe = &rq_ring.rqes[(rq_ring.rq_tail & rq_mask)];
+	rqe->off = (rcqe->off & ~IORING_ZCRX_AREA_MASK) | area_token;
+	rqe->len = cqe->res;
+	io_uring_smp_store_release(rq_ring.ktail, ++rq_ring.rq_tail);
+}
+
+static void server_loop(struct io_uring *ring)
+{
+	struct io_uring_cqe *cqe;
+	unsigned int count = 0;
+	unsigned int head;
+	int i, ret;
+
+	io_uring_submit_and_wait(ring, 1);
+
+	io_uring_for_each_cqe(ring, head, cqe) {
+		if (cqe->user_data == 1)
+			process_accept(ring, cqe);
+		else if (cqe->user_data == 2)
+			process_recvzc(ring, cqe);
+		else
+			error(1, 0, "unknown cqe");
+		count++;
+	}
+	io_uring_cq_advance(ring, count);
+}
+
+static void run_server(void)
+{
+	unsigned int flags = 0;
+	struct io_uring ring;
+	int fd, enable, ret;
+	uint64_t tstop;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1)
+		error(1, 0, "socket()");
+
+	enable = 1;
+	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
+	if (ret < 0)
+		error(1, 0, "setsockopt(SO_REUSEADDR)");
+
+	ret = bind(fd, (struct sockaddr *)&cfg_addr, sizeof(cfg_addr));
+	if (ret < 0)
+		error(1, 0, "bind()");
+
+	if (listen(fd, 1024) < 0)
+		error(1, 0, "listen()");
+
+	flags |= IORING_SETUP_COOP_TASKRUN;
+	flags |= IORING_SETUP_SINGLE_ISSUER;
+	flags |= IORING_SETUP_DEFER_TASKRUN;
+	flags |= IORING_SETUP_SUBMIT_ALL;
+	flags |= IORING_SETUP_CQE32;
+
+	io_uring_queue_init(512, &ring, flags);
+
+	setup_zcrx(&ring);
+
+	add_accept(&ring, fd);
+
+	tstop = gettimeofday_ms() + 5000;
+	while (!stop && gettimeofday_ms() < tstop)
+		server_loop(&ring);
+
+	if (!stop)
+		error(1, 0, "test failed\n");
+}
+
+static void run_client(void)
+{
+	ssize_t to_send = SEND_SIZE;
+	ssize_t sent = 0;
+	ssize_t chunk, res;
+	int fd;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1)
+		error(1, 0, "socket()");
+
+	if (connect(fd, (struct sockaddr *)&cfg_addr, sizeof(cfg_addr)))
+		error(1, 0, "connect()");
+
+	while (to_send) {
+		void *src = &payload[sent];
+
+		chunk = min_t(ssize_t, cfg_payload_len, to_send);
+		res = send(fd, src, chunk, 0);
+		if (res < 0)
+			error(1, 0, "send(): %d", sent);
+		sent += res;
+		to_send -= res;
+	}
+
+	close(fd);
+}
+
+static void usage(const char *filepath)
+{
+	error(1, 0, "Usage: %s (-4|-6) (-s|-c) -h<server_ip> -p<port> "
+		    "-l<payload_size> -i<ifname> -q<rxq_id>", filepath);
+}
+
+static void parse_opts(int argc, char **argv)
+{
+	const int max_payload_len = sizeof(payload) -
+				    sizeof(struct ipv6hdr) -
+				    sizeof(struct tcphdr) -
+				    40 /* max tcp options */;
+	struct sockaddr_in6 *addr6 = (void *) &cfg_addr;
+	char *addr = NULL;
+	int ret;
+	int c;
+
+	if (argc <= 1)
+		usage(argv[0]);
+	cfg_payload_len = max_payload_len;
+
+	while ((c = getopt(argc, argv, "46sch:p:l:i:q:")) != -1) {
+		switch (c) {
+		case 's':
+			if (cfg_client)
+				error(1, 0, "Pass one of -s or -c");
+			cfg_server = 1;
+			break;
+		case 'c':
+			if (cfg_server)
+				error(1, 0, "Pass one of -s or -c");
+			cfg_client = 1;
+			break;
+		case 'h':
+			addr = optarg;
+			break;
+		case 'p':
+			cfg_port = strtoul(optarg, NULL, 0);
+			break;
+		case 'l':
+			cfg_payload_len = strtoul(optarg, NULL, 0);
+			break;
+		case 'i':
+			cfg_ifname = optarg;
+			break;
+		case 'q':
+			cfg_queue_id = strtoul(optarg, NULL, 0);
+			break;
+		}
+	}
+
+	if (cfg_server && addr)
+		error(1, 0, "Receiver cannot have -h specified");
+
+	memset(addr6, 0, sizeof(*addr6));
+	addr6->sin6_family = AF_INET6;
+	addr6->sin6_port = htons(cfg_port);
+	addr6->sin6_addr = in6addr_any;
+	if (addr) {
+		ret = parse_address(addr, cfg_port, addr6);
+		if (ret)
+			error(1, 0, "receiver address parse error: %s", addr);
+	}
+
+	if (cfg_payload_len > max_payload_len)
+		error(1, 0, "-l: payload exceeds max (%d)", max_payload_len);
+}
+
+int main(int argc, char **argv)
+{
+	const char *cfg_test = argv[argc - 1];
+	int i;
+
+	parse_opts(argc, argv);
+
+	for (i = 0; i < SEND_SIZE; i++)
+		payload[i] = 'a' + (i % 26);
+
+	if (cfg_server)
+		run_server();
+	else if (cfg_client)
+		run_client();
+
+	return 0;
+}
diff --git a/tools/testing/selftests/drivers/net/hw/iou-zcrx.py b/tools/testing/selftests/drivers/net/hw/iou-zcrx.py
new file mode 100755
index 000000000000..ea0a346c3eff
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/hw/iou-zcrx.py
@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import re
+from os import path
+from lib.py import ksft_run, ksft_exit
+from lib.py import NetDrvEpEnv
+from lib.py import bkg, cmd, ethtool, wait_port_listen
+
+
+def _get_rx_ring_entries(cfg):
+    output = ethtool(f"-g {cfg.ifname}", host=cfg.remote).stdout
+    values = re.findall(r'RX:\s+(\d+)', output)
+    return int(values[1])
+
+
+def _get_combined_channels(cfg):
+    output = ethtool(f"-l {cfg.ifname}", host=cfg.remote).stdout
+    values = re.findall(r'Combined:\s+(\d+)', output)
+    return int(values[1])
+
+
+def _set_flow_rule(cfg, chan):
+    output = ethtool(f"-N {cfg.ifname} flow-type tcp6 dst-port 9999 action {chan}", host=cfg.remote).stdout
+    values = re.search(r'ID (\d+)', output).group(1)
+    return int(values)
+
+
+def test_zcrx(cfg) -> None:
+    cfg.require_v6()
+
+    combined_chans = _get_combined_channels(cfg)
+    if combined_chans < 2:
+        raise KsftSkipEx('at least 2 combined channels required')
+    rx_ring = _get_rx_ring_entries(cfg)
+
+    rx_cmd = f"{cfg.bin_remote} -s -p 9999 -i {cfg.ifname} -q {combined_chans - 1}"
+    tx_cmd = f"{cfg.bin_local} -c -h {cfg.remote_v6} -p 9999 -l 12840"
+
+    try:
+        ethtool(f"-G {cfg.ifname} rx 64", host=cfg.remote)
+        ethtool(f"-X {cfg.ifname} equal {combined_chans - 1}", host=cfg.remote)
+        flow_rule_id = _set_flow_rule(cfg, combined_chans - 1)
+
+        with bkg(rx_cmd, host=cfg.remote, exit_wait=True):
+            wait_port_listen(9999, proto="tcp", host=cfg.remote)
+            cmd(tx_cmd)
+    finally:
+        ethtool(f"-N {cfg.ifname} delete {flow_rule_id}", host=cfg.remote)
+        ethtool(f"-X {cfg.ifname} default", host=cfg.remote)
+        ethtool(f"-G {cfg.ifname} rx {rx_ring}", host=cfg.remote)
+
+
+def main() -> None:
+    with NetDrvEpEnv(__file__) as cfg:
+        cfg.bin_local = path.abspath(path.dirname(__file__) + "/../../../drivers/net/hw/iou-zcrx")
+        cfg.bin_remote = cfg.remote.deploy(cfg.bin_local)
+
+        ksft_run(globs=globals(), case_pfx={"test_"}, args=(cfg, ))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()
-- 
2.43.5

Re: [PATCH v14 00/11] io_uring zero copy rx

[Jakub Kicinski]

On Fri, 14 Feb 2025 16:09:35 -0800 David Wei wrote:
> This patchset contains io_uring patches needed by a new io_uring request
> implementing zero copy rx into userspace pages, eliminating a kernel to
> user copy.

Acked-by: Jakub Kicinski <kuba@kernel.org>

Re: [PATCH v14 00/11] io_uring zero copy rx

[Jens Axboe]

On Fri, 14 Feb 2025 16:09:35 -0800, David Wei wrote:
> This patchset contains io_uring patches needed by a new io_uring request
> implementing zero copy rx into userspace pages, eliminating a kernel to
> user copy.
> 
> We configure a page pool that a driver uses to fill a hw rx queue to
> hand out user pages instead of kernel pages. Any data that ends up
> hitting this hw rx queue will thus be dma'd into userspace memory
> directly, without needing to be bounced through kernel memory. 'Reading'
> data out of a socket instead becomes a _notification_ mechanism, where
> the kernel tells userspace where the data is. The overall approach is
> similar to the devmem TCP proposal.
> 
> [...]

Applied, thanks!

[01/11] io_uring/zcrx: add interface queue and refill queue
        commit: 6f377873cb23905009759b7366b9fe85c2a6ff37
[02/11] io_uring/zcrx: add io_zcrx_area
        commit: cf96310c5f9a0d542db99c887742811425ba2ec0
[03/11] io_uring/zcrx: grab a net device
        commit: 035af94b39fd13751abf5f0a2948c9eddede55d0
[04/11] io_uring/zcrx: implement zerocopy receive pp memory provider
        commit: 34a3e60821ab9f335a58d43a88cccdbefdebdec3
[05/11] io_uring/zcrx: dma-map area for the device
        commit: db070446f5af8c7a384b89367a10cddbf5498717
[06/11] io_uring/zcrx: add io_recvzc request
        commit: 11ed914bbf948c4a37248f2876973ac18014056d
[07/11] io_uring/zcrx: set pp memory provider for an rx queue
        commit: e0793de24a9f610bd8ce106f7033b3966e7fca0e
[08/11] io_uring/zcrx: throttle receive requests
        commit: 931dfae19032d13266cf1fac080cec66469a2042
[09/11] io_uring/zcrx: add copy fallback
        commit: bc57c7d36c4c9c352ed13d98a4f1e4dc27919d6a
[10/11] net: add documentation for io_uring zcrx
        commit: d9ac1d5fc9510a170eb43e8c129b8e1cd5e1c3e1
[11/11] io_uring/zcrx: add selftest
        commit: 71082faa2c648a2adc1167b37565e195a8df1bc7

Best regards,
-- 
Jens Axboe

Re: [PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx queue

[Kees Bakker]

Op 15-02-2025 om 01:09 schreef David Wei:
> Set the page pool memory provider for the rx queue configured for zero
> copy to io_uring. Then the rx queue is reset using
> netdev_rx_queue_restart() and netdev core + page pool will take care of
> filling the rx queue from the io_uring zero copy memory provider.
>
> For now, there is only one ifq so its destruction happens implicitly
> during io_uring cleanup.
>
> Reviewed-by: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: David Wei <dw@davidwei.uk>
> ---
>   io_uring/zcrx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
>   1 file changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> index 8833879d94ba..7d24fc98b306 100644
> --- a/io_uring/zcrx.c
> +++ b/io_uring/zcrx.c
> [...]
> @@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
>   
>   	if (ctx->ifq)
>   		io_zcrx_scrub(ctx->ifq);
> +
> +	io_close_queue(ctx->ifq);
If ctx->ifq is NULL (which seems to be not unlikely given the if 
statement above)
then you'll get a NULL pointer dereference in io_close_queue().
>   }
>   
>   static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)

Re: [PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx queue

[David Wei]

On 2025-02-18 11:40, Kees Bakker wrote:
> Op 15-02-2025 om 01:09 schreef David Wei:
>> Set the page pool memory provider for the rx queue configured for zero
>> copy to io_uring. Then the rx queue is reset using
>> netdev_rx_queue_restart() and netdev core + page pool will take care of
>> filling the rx queue from the io_uring zero copy memory provider.
>>
>> For now, there is only one ifq so its destruction happens implicitly
>> during io_uring cleanup.
>>
>> Reviewed-by: Jens Axboe <axboe@kernel.dk>
>> Signed-off-by: David Wei <dw@davidwei.uk>
>> ---
>>   io_uring/zcrx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
>>   1 file changed, 41 insertions(+), 8 deletions(-)
>>
>> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
>> index 8833879d94ba..7d24fc98b306 100644
>> --- a/io_uring/zcrx.c
>> +++ b/io_uring/zcrx.c
>> [...]
>> @@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
>>         if (ctx->ifq)
>>           io_zcrx_scrub(ctx->ifq);
>> +
>> +    io_close_queue(ctx->ifq);
> If ctx->ifq is NULL (which seems to be not unlikely given the if statement above)
> then you'll get a NULL pointer dereference in io_close_queue().

The only caller of io_shutdown_zcrx_ifqs() is io_ring_exit_work() which
checks for ctx->ifq first. That does mean the ctx->ifq check is
redundant in this function though.

>>   }
>>     static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)
> 

Re: [PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx queue

[Pavel Begunkov]

On 2/18/25 22:06, David Wei wrote:
> On 2025-02-18 11:40, Kees Bakker wrote:
>> Op 15-02-2025 om 01:09 schreef David Wei:
>>> Set the page pool memory provider for the rx queue configured for zero
>>> copy to io_uring. Then the rx queue is reset using
>>> netdev_rx_queue_restart() and netdev core + page pool will take care of
>>> filling the rx queue from the io_uring zero copy memory provider.
>>>
>>> For now, there is only one ifq so its destruction happens implicitly
>>> during io_uring cleanup.
>>>
>>> Reviewed-by: Jens Axboe <axboe@kernel.dk>
>>> Signed-off-by: David Wei <dw@davidwei.uk>
>>> ---
>>>    io_uring/zcrx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
>>>    1 file changed, 41 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
>>> index 8833879d94ba..7d24fc98b306 100644
>>> --- a/io_uring/zcrx.c
>>> +++ b/io_uring/zcrx.c
>>> [...]
>>> @@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
>>>          if (ctx->ifq)
>>>            io_zcrx_scrub(ctx->ifq);
>>> +
>>> +    io_close_queue(ctx->ifq);
>> If ctx->ifq is NULL (which seems to be not unlikely given the if statement above)
>> then you'll get a NULL pointer dereference in io_close_queue().
> 
> The only caller of io_shutdown_zcrx_ifqs() is io_ring_exit_work() which
> checks for ctx->ifq first. That does mean the ctx->ifq check is
> redundant in this function though.

And despite the check being outside of the lock, it's even well
synchronised, but in any case we should just make it saner. Thanks
for letting know

-- 
Pavel Begunkov