Merge branch 'device-memory-tcp'

Mina Almasry says:

====================
Device Memory TCP

Device memory TCP (devmem TCP) is a proposal for transferring data
to and/or from device memory efficiently, without bouncing the data
to a host memory buffer.

* Problem:

A large amount of data transfers have device memory as the source
and/or destination. Accelerators drastically increased the volume
of such transfers. Some examples include:

- ML accelerators transferring large amounts of training data from storage
into GPU/TPU memory. In some cases ML training setup time can be as long
as 50% of TPU compute time, improving data transfer throughput &
efficiency can help improving GPU/TPU utilization.

- Distributed training, where ML accelerators, such as GPUs on different
hosts, exchange data among them.

- Distributed raw block storage applications transfer large amounts of
data with remote SSDs, much of this data does not require host
processing.

Today, the majority of the Device-to-Device data transfers the network
are implemented as the following low level operations: Device-to-Host
copy, Host-to-Host network transfer, and Host-to-Device copy.

The implementation is suboptimal, especially for bulk data transfers,
and can put significant strains on system resources, such as host memory
bandwidth, PCIe bandwidth, etc. One important reason behind the current
state is the kernel’s lack of semantics to express device to network
transfers.

* Proposal:

In this patch series we attempt to optimize this use case by implementing
socket APIs that enable the user to:

1. send device memory across the network directly, and
2. receive incoming network packets directly into device memory.

Packet _payloads_ go directly from the NIC to device memory for receive
and from device memory to NIC for transmit.
Packet _headers_ go to/from host memory and are processed by the TCP/IP
stack normally. The NIC _must_ support header split to achieve this.

Advantages:

- Alleviate host memory bandwidth pressure, compared to existing
network-transfer + device-copy semantics.

- Alleviate PCIe BW pressure, by limiting data transfer to the lowest level
of the PCIe tree, compared to traditional path which sends data through
the root complex.

* Patch overview:

** Part 1: netlink API

Gives user ability to bind dma-buf to an RX queue.

** Part 2: scatterlist support

Currently the standard for device memory sharing is DMABUF, which doesn't
generate struct pages. On the other hand, networking stack (skbs, drivers,
and page pool) operate on pages. We have 2 options:

1. Generate struct pages for dmabuf device memory, or,
2. Modify the networking stack to process scatterlist.

Approach #1 was attempted in RFC v1. RFC v2 implements approach #2.

** part 3: page pool support

We piggy back on page pool memory providers proposal:
https://github.com/kuba-moo/linux/tree/pp-providers

It allows the page pool to define a memory provider that provides the
page allocation and freeing. It helps abstract most of the device memory
TCP changes from the driver.

** part 4: support for unreadable skb frags

Page pool iovs are not accessible by the host; we implement changes
throughput the networking stack to correctly handle skbs with unreadable
frags.

** Part 5: recvmsg() APIs

We define user APIs for the user to send and receive device memory.

Not included with this series is the GVE devmem TCP support, just to
simplify the review. Code available here if desired:
https://github.com/mina/linux/tree/tcpdevmem

This series is built on top of net-next with Jakub's pp-providers changes
cherry-picked.

* NIC dependencies:

1. (strict) Devmem TCP require the NIC to support header split, i.e. the
capability to split incoming packets into a header + payload and to put
each into a separate buffer. Devmem TCP works by using device memory
for the packet payload, and host memory for the packet headers.

2. (optional) Devmem TCP works better with flow steering support & RSS
support, i.e. the NIC's ability to steer flows into certain rx queues.
This allows the sysadmin to enable devmem TCP on a subset of the rx
queues, and steer devmem TCP traffic onto these queues and non devmem
TCP elsewhere.

The NIC I have access to with these properties is the GVE with DQO support
running in Google Cloud, but any NIC that supports these features would
suffice. I may be able to help reviewers bring up devmem TCP on their NICs.

* Testing:

The series includes a udmabuf kselftest that show a simple use case of
devmem TCP and validates the entire data path end to end without
a dependency on a specific dmabuf provider.

** Test Setup

Kernel: net-next with this series and memory provider API cherry-picked
locally.

Hardware: Google Cloud A3 VMs.

NIC: GVE with header split & RSS & flow steering support.
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/netlink/specs/netdev.yaml

···
           "re-attached", they are just waiting to disappear.
           Attribute is absent if Page Pool has not been detached, and
           can still be used to allocate new memory.
+      -
+        name: dmabuf
+        doc: ID of the dmabuf this page-pool is attached to.
+        type: u32
   -
     name: page-pool-info
     subset-of: page-pool
···
       -
         name: napi-id
         doc: ID of the NAPI instance which services this queue.
+        type: u32
+      -
+        name: dmabuf
+        doc: ID of the dmabuf attached to this queue, if any.
         type: u32
 
   -
···
           Number of times driver re-started accepting send
           requests to this queue from the stack.
         type: uint
+  -
+    name: queue-id
+    subset-of: queue
+    attributes:
+      -
+        name: id
+      -
+        name: type
+  -
+    name: dmabuf
+    attributes:
+      -
+        name: ifindex
+        doc: netdev ifindex to bind the dmabuf to.
+        type: u32
+        checks:
+          min: 1
+      -
+        name: queues
+        doc: receive queues to bind the dmabuf to.
+        type: nest
+        nested-attributes: queue-id
+        multi-attr: true
+      -
+        name: fd
+        doc: dmabuf file descriptor to bind.
+        type: u32
+      -
+        name: id
+        doc: id of the dmabuf binding
+        type: u32
+        checks:
+          min: 1
 
 operations:
   list:
···
             - inflight
             - inflight-mem
             - detach-time
+            - dmabuf
       dump:
         reply: *pp-reply
       config-cond: page-pool
···
             - type
             - napi-id
             - ifindex
+            - dmabuf
       dump:
         request:
           attributes:
···
             - rx-bytes
             - tx-packets
             - tx-bytes
+    -
+      name: bind-rx
+      doc: Bind dmabuf to netdev
+      attribute-set: dmabuf
+      flags: [ admin-perm ]
+      do:
+        request:
+          attributes:
+            - ifindex
+            - fd
+            - queues
+        reply:
+          attributes:
+            - id
+
+kernel-family:
+  headers: [ "linux/list.h"]
+  sock-priv: struct list_head
 
 mcast-groups:
   list:

Documentation/networking/devmem.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Device Memory TCP
+=================
+
+
+Intro
+=====
+
+Device memory TCP (devmem TCP) enables receiving data directly into device
+memory (dmabuf). The feature is currently implemented for TCP sockets.
+
+
+Opportunity
+-----------
+
+A large number of data transfers have device memory as the source and/or
+destination. Accelerators drastically increased the prevalence of such
+transfers.  Some examples include:
+
+- Distributed training, where ML accelerators, such as GPUs on different hosts,
+  exchange data.
+
+- Distributed raw block storage applications transfer large amounts of data with
+  remote SSDs. Much of this data does not require host processing.
+
+Typically the Device-to-Device data transfers in the network are implemented as
+the following low-level operations: Device-to-Host copy, Host-to-Host network
+transfer, and Host-to-Device copy.
+
+The flow involving host copies is suboptimal, especially for bulk data transfers,
+and can put significant strains on system resources such as host memory
+bandwidth and PCIe bandwidth.
+
+Devmem TCP optimizes this use case by implementing socket APIs that enable
+the user to receive incoming network packets directly into device memory.
+
+Packet payloads go directly from the NIC to device memory.
+
+Packet headers go to host memory and are processed by the TCP/IP stack
+normally. The NIC must support header split to achieve this.
+
+Advantages:
+
+- Alleviate host memory bandwidth pressure, compared to existing
+  network-transfer + device-copy semantics.
+
+- Alleviate PCIe bandwidth pressure, by limiting data transfer to the lowest
+  level of the PCIe tree, compared to the traditional path which sends data
+  through the root complex.
+
+
+More Info
+---------
+
+  slides, video
+    https://netdevconf.org/0x17/sessions/talk/device-memory-tcp.html
+
+  patchset
+    [PATCH net-next v24 00/13] Device Memory TCP
+    https://lore.kernel.org/netdev/[e-mail]/
+
+
+Interface
+=========
+
+
+Example
+-------
+
+tools/testing/selftests/net/ncdevmem.c:do_server shows an example of setting up
+the RX path of this API.
+
+
+NIC Setup
+---------
+
+Header split, flow steering, & RSS are required features for devmem TCP.
+
+Header split is used to split incoming packets into a header buffer in host
+memory, and a payload buffer in device memory.
+
+Flow steering & RSS are used to ensure that only flows targeting devmem land on
+an RX queue bound to devmem.
+
+Enable header split & flow steering::
+
+	# enable header split
+	ethtool -G eth1 tcp-data-split on
+
+
+	# enable flow steering
+	ethtool -K eth1 ntuple on
+
+Configure RSS to steer all traffic away from the target RX queue (queue 15 in
+this example)::
+
+	ethtool --set-rxfh-indir eth1 equal 15
+
+
+The user must bind a dmabuf to any number of RX queues on a given NIC using
+the netlink API::
+
+	/* Bind dmabuf to NIC RX queue 15 */
+	struct netdev_queue *queues;
+	queues = malloc(sizeof(*queues) * 1);
+
+	queues[0]._present.type = 1;
+	queues[0]._present.idx = 1;
+	queues[0].type = NETDEV_RX_QUEUE_TYPE_RX;
+	queues[0].idx = 15;
+
+	*ys = ynl_sock_create(&ynl_netdev_family, &yerr);
+
+	req = netdev_bind_rx_req_alloc();
+	netdev_bind_rx_req_set_ifindex(req, 1 /* ifindex */);
+	netdev_bind_rx_req_set_dmabuf_fd(req, dmabuf_fd);
+	__netdev_bind_rx_req_set_queues(req, queues, n_queue_index);
+
+	rsp = netdev_bind_rx(*ys, req);
+
+	dmabuf_id = rsp->dmabuf_id;
+
+
+The netlink API returns a dmabuf_id: a unique ID that refers to this dmabuf
+that has been bound.
+
+The user can unbind the dmabuf from the netdevice by closing the netlink socket
+that established the binding. We do this so that the binding is automatically
+unbound even if the userspace process crashes.
+
+Note that any reasonably well-behaved dmabuf from any exporter should work with
+devmem TCP, even if the dmabuf is not actually backed by devmem. An example of
+this is udmabuf, which wraps user memory (non-devmem) in a dmabuf.
+
+
+Socket Setup
+------------
+
+The socket must be flow steered to the dmabuf bound RX queue::
+
+	ethtool -N eth1 flow-type tcp4 ... queue 15
+
+
+Receiving data
+--------------
+
+The user application must signal to the kernel that it is capable of receiving
+devmem data by passing the MSG_SOCK_DEVMEM flag to recvmsg::
+
+	ret = recvmsg(fd, &msg, MSG_SOCK_DEVMEM);
+
+Applications that do not specify the MSG_SOCK_DEVMEM flag will receive an EFAULT
+on devmem data.
+
+Devmem data is received directly into the dmabuf bound to the NIC in 'NIC
+Setup', and the kernel signals such to the user via the SCM_DEVMEM_* cmsgs::
+
+		for (cm = CMSG_FIRSTHDR(&msg); cm; cm = CMSG_NXTHDR(&msg, cm)) {
+			if (cm->cmsg_level != SOL_SOCKET ||
+				(cm->cmsg_type != SCM_DEVMEM_DMABUF &&
+				 cm->cmsg_type != SCM_DEVMEM_LINEAR))
+				continue;
+
+			dmabuf_cmsg = (struct dmabuf_cmsg *)CMSG_DATA(cm);
+
+			if (cm->cmsg_type == SCM_DEVMEM_DMABUF) {
+				/* Frag landed in dmabuf.
+				 *
+				 * dmabuf_cmsg->dmabuf_id is the dmabuf the
+				 * frag landed on.
+				 *
+				 * dmabuf_cmsg->frag_offset is the offset into
+				 * the dmabuf where the frag starts.
+				 *
+				 * dmabuf_cmsg->frag_size is the size of the
+				 * frag.
+				 *
+				 * dmabuf_cmsg->frag_token is a token used to
+				 * refer to this frag for later freeing.
+				 */
+
+				struct dmabuf_token token;
+				token.token_start = dmabuf_cmsg->frag_token;
+				token.token_count = 1;
+				continue;
+			}
+
+			if (cm->cmsg_type == SCM_DEVMEM_LINEAR)
+				/* Frag landed in linear buffer.
+				 *
+				 * dmabuf_cmsg->frag_size is the size of the
+				 * frag.
+				 */
+				continue;
+
+		}
+
+Applications may receive 2 cmsgs:
+
+- SCM_DEVMEM_DMABUF: this indicates the fragment landed in the dmabuf indicated
+  by dmabuf_id.
+
+- SCM_DEVMEM_LINEAR: this indicates the fragment landed in the linear buffer.
+  This typically happens when the NIC is unable to split the packet at the
+  header boundary, such that part (or all) of the payload landed in host
+  memory.
+
+Applications may receive no SO_DEVMEM_* cmsgs. That indicates non-devmem,
+regular TCP data that landed on an RX queue not bound to a dmabuf.
+
+
+Freeing frags
+-------------
+
+Frags received via SCM_DEVMEM_DMABUF are pinned by the kernel while the user
+processes the frag. The user must return the frag to the kernel via
+SO_DEVMEM_DONTNEED::
+
+	ret = setsockopt(client_fd, SOL_SOCKET, SO_DEVMEM_DONTNEED, &token,
+			 sizeof(token));
+
+The user must ensure the tokens are returned to the kernel in a timely manner.
+Failure to do so will exhaust the limited dmabuf that is bound to the RX queue
+and will lead to packet drops.
+
+
+Implementation & Caveats
+========================
+
+Unreadable skbs
+---------------
+
+Devmem payloads are inaccessible to the kernel processing the packets. This
+results in a few quirks for payloads of devmem skbs:
+
+- Loopback is not functional. Loopback relies on copying the payload, which is
+  not possible with devmem skbs.
+
+- Software checksum calculation fails.
+
+- TCP Dump and bpf can't access devmem packet payloads.
+
+
+Testing
+=======
+
+More realistic example code can be found in the kernel source under
+``tools/testing/selftests/net/ncdevmem.c``
+
+ncdevmem is a devmem TCP netcat. It works very similarly to netcat, but
+receives data directly into a udmabuf.
+
+To run ncdevmem, you need to run it on a server on the machine under test, and
+you need to run netcat on a peer to provide the TX data.
+
+ncdevmem has a validation mode as well that expects a repeating pattern of
+incoming data and validates it as such. For example, you can launch
+ncdevmem on the server by::
+
+	ncdevmem -s <server IP> -c <client IP> -f eth1 -d 3 -n 0000:06:00.0 -l \
+		 -p 5201 -v 7
+
+On client side, use regular netcat to send TX data to ncdevmem process
+on the server::
+
+	yes $(echo -e \\x01\\x02\\x03\\x04\\x05\\x06) | \
+		tr \\n \\0 | head -c 5G | nc <server IP> 5201 -p 5201

Documentation/networking/index.rst

···
    cdc_mbim
    dccp
    dctcp
+   devmem
    dns_resolver
    driver
    eql

arch/alpha/include/uapi/asm/socket.h

···
 #define SO_PASSPIDFD		76
 #define SO_PEERPIDFD		77
 
+#define SO_DEVMEM_LINEAR	78
+#define SCM_DEVMEM_LINEAR	SO_DEVMEM_LINEAR
+#define SO_DEVMEM_DMABUF	79
+#define SCM_DEVMEM_DMABUF	SO_DEVMEM_DMABUF
+#define SO_DEVMEM_DONTNEED	80
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/mips/include/uapi/asm/socket.h

···
 #define SO_PASSPIDFD		76
 #define SO_PEERPIDFD		77
 
+#define SO_DEVMEM_LINEAR	78
+#define SCM_DEVMEM_LINEAR	SO_DEVMEM_LINEAR
+#define SO_DEVMEM_DMABUF	79
+#define SCM_DEVMEM_DMABUF	SO_DEVMEM_DMABUF
+#define SO_DEVMEM_DONTNEED	80
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/parisc/include/uapi/asm/socket.h

···
 #define SO_PASSPIDFD		0x404A
 #define SO_PEERPIDFD		0x404B
 
+#define SO_DEVMEM_LINEAR	78
+#define SCM_DEVMEM_LINEAR	SO_DEVMEM_LINEAR
+#define SO_DEVMEM_DMABUF	79
+#define SCM_DEVMEM_DMABUF	SO_DEVMEM_DMABUF
+#define SO_DEVMEM_DONTNEED	80
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64

arch/sparc/include/uapi/asm/socket.h

···
 #define SO_PASSPIDFD             0x0055
 #define SO_PEERPIDFD             0x0056
 
+#define SO_DEVMEM_LINEAR         0x0057
+#define SCM_DEVMEM_LINEAR        SO_DEVMEM_LINEAR
+#define SO_DEVMEM_DMABUF         0x0058
+#define SCM_DEVMEM_DMABUF        SO_DEVMEM_DMABUF
+#define SO_DEVMEM_DONTNEED       0x0059
+
 #if !defined(__KERNEL__)
 
 

include/linux/netdevice.h

···
 int dev_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf);
 u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode);
 
+u32 dev_get_min_mp_channel_count(const struct net_device *dev);
+
 int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
 int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
 int dev_forward_skb_nomtu(struct net_device *dev, struct sk_buff *skb);

include/linux/skbuff.h

···
  *	@csum_level: indicates the number of consecutive checksums found in
  *		the packet minus one that have been verified as
  *		CHECKSUM_UNNECESSARY (max 3)
+ *	@unreadable: indicates that at least 1 of the fragments in this skb is
+ *		unreadable.
  *	@dst_pending_confirm: need to confirm neighbour
  *	@decrypted: Decrypted SKB
  *	@slow_gro: state present at GRO time, slower prepare step required
···
 #if IS_ENABLED(CONFIG_IP_SCTP)
 	__u8			csum_not_inet:1;
 #endif
-
+	__u8			unreadable:1;
 #if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS)
 	__u16			tc_index;	/* traffic control index */
 #endif
···
 		__skb_zcopy_downgrade_managed(skb);
 }
 
+/* Return true if frags in this skb are readable by the host. */
+static inline bool skb_frags_readable(const struct sk_buff *skb)
+{
+	return !skb->unreadable;
+}
+
 static inline void skb_mark_not_on_list(struct sk_buff *skb)
 {
 	skb->next = NULL;
···
 static inline void __skb_fill_netmem_desc(struct sk_buff *skb, int i,
 					  netmem_ref netmem, int off, int size)
 {
-	struct page *page = netmem_to_page(netmem);
+	struct page *page;
 
 	__skb_fill_netmem_desc_noacc(skb_shinfo(skb), i, netmem, off, size);
+
+	if (netmem_is_net_iov(netmem)) {
+		skb->unreadable = true;
+		return;
+	}
+
+	page = netmem_to_page(netmem);
 
 	/* Propagate page pfmemalloc to the skb if we can. The problem is
 	 * that not all callers have unique ownership of the page but rely
···
 	fragto->offset = fragfrom->offset;
 }
 
+/* Return: true if the skb_frag contains a net_iov. */
+static inline bool skb_frag_is_net_iov(const skb_frag_t *frag)
+{
+	return netmem_is_net_iov(frag->netmem);
+}
+
+/**
+ * skb_frag_net_iov - retrieve the net_iov referred to by fragment
+ * @frag: the fragment
+ *
+ * Return: the &struct net_iov associated with @frag. Returns NULL if this
+ * frag has no associated net_iov.
+ */
+static inline struct net_iov *skb_frag_net_iov(const skb_frag_t *frag)
+{
+	if (!skb_frag_is_net_iov(frag))
+		return NULL;
+
+	return netmem_to_net_iov(frag->netmem);
+}
+
 /**
  * skb_frag_page - retrieve the page referred to by a paged fragment
  * @frag: the paged fragment
  *
- * Returns the &struct page associated with @frag.
+ * Return: the &struct page associated with @frag. Returns NULL if this frag
+ * has no associated page.
  */
 static inline struct page *skb_frag_page(const skb_frag_t *frag)
 {
+	if (skb_frag_is_net_iov(frag))
+		return NULL;
+
 	return netmem_to_page(frag->netmem);
+}
+
+/**
+ * skb_frag_netmem - retrieve the netmem referred to by a fragment
+ * @frag: the fragment
+ *
+ * Return: the &netmem_ref associated with @frag.
+ */
+static inline netmem_ref skb_frag_netmem(const skb_frag_t *frag)
+{
+	return frag->netmem;
 }
 
 int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
 		    unsigned int headroom);
 int skb_cow_data_for_xdp(struct page_pool *pool, struct sk_buff **pskb,
 			 struct bpf_prog *prog);
+
 /**
  * skb_frag_address - gets the address of the data contained in a paged fragment
  * @frag: the paged fragment buffer
···
  */
 static inline void *skb_frag_address(const skb_frag_t *frag)
 {
+	if (!skb_frag_page(frag))
+		return NULL;
+
 	return page_address(skb_frag_page(frag)) + skb_frag_off(frag);
 }
 

include/linux/skbuff_ref.h

···
 
 bool napi_pp_put_page(netmem_ref netmem);
 
-static inline void
-skb_page_unref(struct page *page, bool recycle)
+static inline void skb_page_unref(netmem_ref netmem, bool recycle)
 {
 #ifdef CONFIG_PAGE_POOL
-	if (recycle && napi_pp_put_page(page_to_netmem(page)))
+	if (recycle && napi_pp_put_page(netmem))
 		return;
 #endif
-	put_page(page);
+	put_page(netmem_to_page(netmem));
 }
 
 /**
···
  */
 static inline void __skb_frag_unref(skb_frag_t *frag, bool recycle)
 {
-	skb_page_unref(skb_frag_page(frag), recycle);
+	skb_page_unref(skb_frag_netmem(frag), recycle);
 }
 
 /**

include/linux/socket.h

···
 					  * plain text and require encryption
 					  */
 
+#define MSG_SOCK_DEVMEM 0x2000000	/* Receive devmem skbs as cmsg */
 #define MSG_ZEROCOPY	0x4000000	/* Use user data in kernel path */
 #define MSG_SPLICE_PAGES 0x8000000	/* Splice the pages from the iterator in sendmsg() */
 #define MSG_FASTOPEN	0x20000000	/* Send data in TCP SYN */

include/net/netdev_rx_queue.h

···
 #include <linux/netdevice.h>
 #include <linux/sysfs.h>
 #include <net/xdp.h>
+#include <net/page_pool/types.h>
 
 /* This structure contains an instance of an RX queue. */
 struct netdev_rx_queue {
···
 	 * Readers and writers must hold RTNL
 	 */
 	struct napi_struct		*napi;
+	struct pp_memory_provider_params mp_params;
 } ____cacheline_aligned_in_smp;
 
 /*
···
 	return index;
 }
 #endif
+
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+
 #endif

include/net/netmem.h

···
 #ifndef _NET_NETMEM_H
 #define _NET_NETMEM_H
 
+#include <linux/mm.h>
+#include <net/net_debug.h>
+
+/* net_iov */
+
+DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
+
+/*  We overload the LSB of the struct page pointer to indicate whether it's
+ *  a page or net_iov.
+ */
+#define NET_IOV 0x01UL
+
+struct net_iov {
+	unsigned long __unused_padding;
+	unsigned long pp_magic;
+	struct page_pool *pp;
+	struct dmabuf_genpool_chunk_owner *owner;
+	unsigned long dma_addr;
+	atomic_long_t pp_ref_count;
+};
+
+/* These fields in struct page are used by the page_pool and net stack:
+ *
+ *        struct {
+ *                unsigned long pp_magic;
+ *                struct page_pool *pp;
+ *                unsigned long _pp_mapping_pad;
+ *                unsigned long dma_addr;
+ *                atomic_long_t pp_ref_count;
+ *        };
+ *
+ * We mirror the page_pool fields here so the page_pool can access these fields
+ * without worrying whether the underlying fields belong to a page or net_iov.
+ *
+ * The non-net stack fields of struct page are private to the mm stack and must
+ * never be mirrored to net_iov.
+ */
+#define NET_IOV_ASSERT_OFFSET(pg, iov)             \
+	static_assert(offsetof(struct page, pg) == \
+		      offsetof(struct net_iov, iov))
+NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);
+NET_IOV_ASSERT_OFFSET(pp, pp);
+NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);
+NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
+#undef NET_IOV_ASSERT_OFFSET
+
+/* netmem */
+
 /**
  * typedef netmem_ref - a nonexistent type marking a reference to generic
  * network memory.
···
  */
 typedef unsigned long __bitwise netmem_ref;
 
+static inline bool netmem_is_net_iov(const netmem_ref netmem)
+{
+	return (__force unsigned long)netmem & NET_IOV;
+}
+
 /* This conversion fails (returns NULL) if the netmem_ref is not struct page
  * backed.
- *
- * Currently struct page is the only possible netmem, and this helper never
- * fails.
  */
 static inline struct page *netmem_to_page(netmem_ref netmem)
 {
+	if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
+		return NULL;
+
 	return (__force struct page *)netmem;
 }
 
-/* Converting from page to netmem is always safe, because a page can always be
- * a netmem.
- */
+static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
+{
+	if (netmem_is_net_iov(netmem))
+		return (struct net_iov *)((__force unsigned long)netmem &
+					  ~NET_IOV);
+
+	DEBUG_NET_WARN_ON_ONCE(true);
+	return NULL;
+}
+
+static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
+{
+	return (__force netmem_ref)((unsigned long)niov | NET_IOV);
+}
+
 static inline netmem_ref page_to_netmem(struct page *page)
 {
 	return (__force netmem_ref)page;
···
 
 static inline int netmem_ref_count(netmem_ref netmem)
 {
+	/* The non-pp refcount of net_iov is always 1. On net_iov, we only
+	 * support pp refcounting which uses the pp_ref_count field.
+	 */
+	if (netmem_is_net_iov(netmem))
+		return 1;
+
 	return page_ref_count(netmem_to_page(netmem));
 }
 
-static inline unsigned long netmem_to_pfn(netmem_ref netmem)
+static inline unsigned long netmem_pfn_trace(netmem_ref netmem)
 {
+	if (netmem_is_net_iov(netmem))
+		return 0;
+
 	return page_to_pfn(netmem_to_page(netmem));
+}
+
+static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
+{
+	return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);
+}
+
+static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
+{
+	return __netmem_clear_lsb(netmem)->pp;
+}
+
+static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
+{
+	return &__netmem_clear_lsb(netmem)->pp_ref_count;
+}
+
+static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
+{
+	/* NUMA node preference only makes sense if we're allocating
+	 * system memory. Memory providers (which give us net_iovs)
+	 * choose for us.
+	 */
+	if (netmem_is_net_iov(netmem))
+		return true;
+
+	return page_to_nid(netmem_to_page(netmem)) == pref_nid;
 }
 
 static inline netmem_ref netmem_compound_head(netmem_ref netmem)
 {
+	/* niov are never compounded */
+	if (netmem_is_net_iov(netmem))
+		return netmem;
+
 	return page_to_netmem(compound_head(netmem_to_page(netmem)));
+}
+
+static inline void *netmem_address(netmem_ref netmem)
+{
+	if (netmem_is_net_iov(netmem))
+		return NULL;
+
+	return page_address(netmem_to_page(netmem));
+}
+
+static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
+{
+	return __netmem_clear_lsb(netmem)->dma_addr;
 }
 
 #endif /* _NET_NETMEM_H */

include/net/page_pool/helpers.h

···
 
 static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
 {
-	atomic_long_set(&netmem_to_page(netmem)->pp_ref_count, nr);
+	atomic_long_set(netmem_get_pp_ref_count_ref(netmem), nr);
 }
 
 /**
···
 
 static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
 {
-	struct page *page = netmem_to_page(netmem);
+	atomic_long_t *pp_ref_count = netmem_get_pp_ref_count_ref(netmem);
 	long ret;
 
 	/* If nr == pp_ref_count then we have cleared all remaining
···
 	 * initially, and only overwrite it when the page is partitioned into
 	 * more than one piece.
 	 */
-	if (atomic_long_read(&page->pp_ref_count) == nr) {
+	if (atomic_long_read(pp_ref_count) == nr) {
 		/* As we have ensured nr is always one for constant case using
 		 * the BUILD_BUG_ON(), only need to handle the non-constant case
 		 * here for pp_ref_count draining, which is a rare case.
 		 */
 		BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
 		if (!__builtin_constant_p(nr))
-			atomic_long_set(&page->pp_ref_count, 1);
+			atomic_long_set(pp_ref_count, 1);
 
 		return 0;
 	}
 
-	ret = atomic_long_sub_return(nr, &page->pp_ref_count);
+	ret = atomic_long_sub_return(nr, pp_ref_count);
 	WARN_ON(ret < 0);
 
 	/* We are the last user here too, reset pp_ref_count back to 1 to
···
 	 * page_pool_unref_page() currently.
 	 */
 	if (unlikely(!ret))
-		atomic_long_set(&page->pp_ref_count, 1);
+		atomic_long_set(pp_ref_count, 1);
 
 	return ret;
 }
···
 
 static inline dma_addr_t page_pool_get_dma_addr_netmem(netmem_ref netmem)
 {
-	struct page *page = netmem_to_page(netmem);
-
-	dma_addr_t ret = page->dma_addr;
+	dma_addr_t ret = netmem_get_dma_addr(netmem);
 
 	if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
 		ret <<= PAGE_SHIFT;
···
 static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
 {
 	return page_pool_get_dma_addr_netmem(page_to_netmem((struct page *)page));
-}
-
-static inline bool page_pool_set_dma_addr_netmem(netmem_ref netmem,
-						 dma_addr_t addr)
-{
-	struct page *page = netmem_to_page(netmem);
-
-	if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
-		page->dma_addr = addr >> PAGE_SHIFT;
-
-		/* We assume page alignment to shave off bottom bits,
-		 * if this "compression" doesn't work we need to drop.
-		 */
-		return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
-	}
-
-	page->dma_addr = addr;
-	return false;
 }
 
 /**
···
 				      page_pool_get_dma_addr(page),
 				      offset + pool->p.offset, dma_sync_size,
 				      page_pool_get_dma_dir(pool));
-}
-
-static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
-{
-	return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
 }
 
 static inline bool page_pool_put(struct page_pool *pool)

include/net/page_pool/types.h

···
 					* device driver responsibility
 					*/
 #define PP_FLAG_SYSTEM_POOL	BIT(2) /* Global system page_pool */
+
+/* Allow unreadable (net_iov backed) netmem in this page_pool. Drivers setting
+ * this must be able to support unreadable netmem, where netmem_address() would
+ * return NULL. This flag should not be set for header page_pools.
+ *
+ * If the driver sets PP_FLAG_ALLOW_UNREADABLE_NETMEM, it should also set
+ * page_pool_params.slow.queue_idx.
+ */
+#define PP_FLAG_ALLOW_UNREADABLE_NETMEM BIT(3)
+
 #define PP_FLAG_ALL		(PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | \
-				 PP_FLAG_SYSTEM_POOL)
+				 PP_FLAG_SYSTEM_POOL | PP_FLAG_ALLOW_UNREADABLE_NETMEM)
 
 /*
  * Fast allocation side cache array/stack
···
  * @offset:	DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
  * @slow:	params with slowpath access only (initialization and Netlink)
  * @netdev:	netdev this pool will serve (leave as NULL if none or multiple)
- * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL
+ * @queue_idx:	queue idx this page_pool is being created for.
+ * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_SYSTEM_POOL,
+ *		PP_FLAG_ALLOW_UNREADABLE_NETMEM.
  */
 struct page_pool_params {
 	struct_group_tagged(page_pool_params_fast, fast,
···
 	);
 	struct_group_tagged(page_pool_params_slow, slow,
 		struct net_device *netdev;
+		unsigned int queue_idx;
 		unsigned int	flags;
 /* private: used by test code only */
 		void (*init_callback)(netmem_ref netmem, void *arg);
···
  */
 #define PAGE_POOL_FRAG_GROUP_ALIGN	(4 * sizeof(long))
 
+struct pp_memory_provider_params {
+	void *mp_priv;
+};
+
 struct page_pool {
 	struct page_pool_params_fast p;
 
···
 	 * TODO: Implement bulk return pages into this structure.
 	 */
 	struct ptr_ring ring;
+
+	void *mp_priv;
 
 #ifdef CONFIG_PAGE_POOL_STATS
 	/* recycle stats are per-cpu to avoid locking */

include/net/sock.h

···
   *	@sk_txtime_report_errors: set report errors mode for SO_TXTIME
   *	@sk_txtime_unused: unused txtime flags
   *	@ns_tracker: tracker for netns reference
+  *	@sk_user_frags: xarray of pages the user is holding a reference on.
   */
 struct sock {
 	/*
···
 #endif
 	struct rcu_head		sk_rcu;
 	netns_tracker		ns_tracker;
+	struct xarray		sk_user_frags;
 };
 
 struct sock_bh_locked {

include/net/tcp.h

···
 	/* skb_cmp_decrypted() not needed, use tcp_write_collapse_fence() */
 	return likely(tcp_skb_can_collapse_to(to) &&
 		      mptcp_skb_can_collapse(to, from) &&
-		      skb_pure_zcopy_same(to, from));
+		      skb_pure_zcopy_same(to, from) &&
+		      skb_frags_readable(to) == skb_frags_readable(from));
 }
 
 static inline bool tcp_skb_can_collapse_rx(const struct sk_buff *to,

include/trace/events/page_pool.h

···
 		__entry->pool		= pool;
 		__entry->netmem		= (__force unsigned long)netmem;
 		__entry->release	= release;
-		__entry->pfn		= netmem_to_pfn(netmem);
+		__entry->pfn		= netmem_pfn_trace(netmem);
 	),
 
-	TP_printk("page_pool=%p netmem=%p pfn=0x%lx release=%u",
+	TP_printk("page_pool=%p netmem=%p is_net_iov=%lu pfn=0x%lx release=%u",
 		  __entry->pool, (void *)__entry->netmem,
-		  __entry->pfn, __entry->release)
+		  __entry->netmem & NET_IOV, __entry->pfn, __entry->release)
 );
 
 TRACE_EVENT(page_pool_state_hold,
···
 		__entry->pool	= pool;
 		__entry->netmem	= (__force unsigned long)netmem;
 		__entry->hold	= hold;
-		__entry->pfn	= netmem_to_pfn(netmem);
+		__entry->pfn	= netmem_pfn_trace(netmem);
 	),
 
-	TP_printk("page_pool=%p netmem=%p pfn=0x%lx hold=%u",
+	TP_printk("page_pool=%p netmem=%p is_net_iov=%lu, pfn=0x%lx hold=%u",
 		  __entry->pool, (void *)__entry->netmem,
-		  __entry->pfn, __entry->hold)
+		  __entry->netmem & NET_IOV, __entry->pfn, __entry->hold)
 );
 
 TRACE_EVENT(page_pool_update_nid,

include/uapi/asm-generic/socket.h

···
 #define SO_PASSPIDFD		76
 #define SO_PEERPIDFD		77
 
+#define SO_DEVMEM_LINEAR	78
+#define SCM_DEVMEM_LINEAR	SO_DEVMEM_LINEAR
+#define SO_DEVMEM_DMABUF	79
+#define SCM_DEVMEM_DMABUF	SO_DEVMEM_DMABUF
+#define SO_DEVMEM_DONTNEED	80
+
 #if !defined(__KERNEL__)
 
 #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))

include/uapi/linux/netdev.h

···
 	NETDEV_A_PAGE_POOL_INFLIGHT,
 	NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
 	NETDEV_A_PAGE_POOL_DETACH_TIME,
+	NETDEV_A_PAGE_POOL_DMABUF,
 
 	__NETDEV_A_PAGE_POOL_MAX,
 	NETDEV_A_PAGE_POOL_MAX = (__NETDEV_A_PAGE_POOL_MAX - 1)
···
 	NETDEV_A_QUEUE_IFINDEX,
 	NETDEV_A_QUEUE_TYPE,
 	NETDEV_A_QUEUE_NAPI_ID,
+	NETDEV_A_QUEUE_DMABUF,
 
 	__NETDEV_A_QUEUE_MAX,
 	NETDEV_A_QUEUE_MAX = (__NETDEV_A_QUEUE_MAX - 1)
···
 };
 
 enum {
+	NETDEV_A_DMABUF_IFINDEX = 1,
+	NETDEV_A_DMABUF_QUEUES,
+	NETDEV_A_DMABUF_FD,
+	NETDEV_A_DMABUF_ID,
+
+	__NETDEV_A_DMABUF_MAX,
+	NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
+};
+
+enum {
 	NETDEV_CMD_DEV_GET = 1,
 	NETDEV_CMD_DEV_ADD_NTF,
 	NETDEV_CMD_DEV_DEL_NTF,
···
 	NETDEV_CMD_QUEUE_GET,
 	NETDEV_CMD_NAPI_GET,
 	NETDEV_CMD_QSTATS_GET,
+	NETDEV_CMD_BIND_RX,
 
 	__NETDEV_CMD_MAX,
 	NETDEV_CMD_MAX = (__NETDEV_CMD_MAX - 1)

include/uapi/linux/uio.h

···
 	__kernel_size_t iov_len; /* Must be size_t (1003.1g) */
 };
 
+struct dmabuf_cmsg {
+	__u64 frag_offset;	/* offset into the dmabuf where the frag starts.
+				 */
+	__u32 frag_size;	/* size of the frag. */
+	__u32 frag_token;	/* token representing this frag for
+				 * DEVMEM_DONTNEED.
+				 */
+	__u32  dmabuf_id;	/* dmabuf id this frag belongs to. */
+	__u32 flags;		/* Currently unused. Reserved for future
+				 * uses.
+				 */
+};
+
+struct dmabuf_token {
+	__u32 token_start;
+	__u32 token_count;
+};
+
 /*
  *	UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
  */

net/Kconfig

···
 config SKB_EXTENSIONS
 	bool
 
+config NET_DEVMEM
+	def_bool y
+	depends on DMA_SHARED_BUFFER
+	depends on GENERIC_ALLOCATOR
+
 menu "Networking options"
 
 source "net/packet/Kconfig"

net/core/Makefile

···
 
 obj-y += net-sysfs.o
 obj-y += hotdata.o
+obj-y += netdev_rx_queue.o
 obj-$(CONFIG_PAGE_POOL) += page_pool.o page_pool_user.o
 obj-$(CONFIG_PROC_FS) += net-procfs.o
 obj-$(CONFIG_NET_PKTGEN) += pktgen.o
···
 obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o
 obj-$(CONFIG_OF)	+= of_net.o
 obj-$(CONFIG_NET_TEST) += net_test.o
+obj-$(CONFIG_NET_DEVMEM) += devmem.o

net/core/datagram.c

···
 			return 0;
 	}
 
+	if (!skb_frags_readable(skb))
+		goto short_copy;
+
 	/* Copy paged appendix. Hmm... why does this look so complicated? */
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
···
 				struct iov_iter *from, size_t length)
 {
 	int frag = skb_shinfo(skb)->nr_frags;
+
+	if (!skb_frags_readable(skb))
+		return -EFAULT;
 
 	while (length && iov_iter_count(from)) {
 		struct page *head, *last_head = NULL;

net/core/dev.c

···
 #include <linux/phy_link_topology.h>
 
 #include "dev.h"
+#include "devmem.h"
 #include "net-sysfs.h"
 
 static DEFINE_SPINLOCK(ptype_lock);
···
 		return -EINVAL;
 	}
 
+	if (!skb_frags_readable(skb)) {
+		return -EFAULT;
+	}
+
 	/* Before computing a checksum, we should make sure no frag could
 	 * be modified by an external entity : checksum could be wrong.
 	 */
···
 	if (!(dev->features & NETIF_F_HIGHDMA)) {
 		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+			struct page *page = skb_frag_page(frag);
 
-			if (PageHighMem(skb_frag_page(frag)))
+			if (page && PageHighMem(page))
 				return 1;
 		}
 	}
···
 	if (!dev->netdev_ops->ndo_bpf)
 		return -EOPNOTSUPP;
 
+	if (dev_get_min_mp_channel_count(dev)) {
+		NL_SET_ERR_MSG(bpf->extack, "unable to propagate XDP to device using memory provider");
+		return -EBUSY;
+	}
+
 	return dev->netdev_ops->ndo_bpf(dev, bpf);
 }
 EXPORT_SYMBOL_GPL(dev_xdp_propagate);
···
 {
 	struct netdev_bpf xdp;
 	int err;
+
+	if (dev_get_min_mp_channel_count(dev)) {
+		NL_SET_ERR_MSG(extack, "unable to install XDP to device using memory provider");
+		return -EBUSY;
+	}
 
 	memset(&xdp, 0, sizeof(xdp));
 	xdp.command = mode == XDP_MODE_HW ? XDP_SETUP_PROG_HW : XDP_SETUP_PROG;
···
 	if (old_prog)
 		bpf_prog_put(old_prog);
 	return err;
+}
+
+u32 dev_get_min_mp_channel_count(const struct net_device *dev)
+{
+	int i;
+
+	ASSERT_RTNL();
+
+	for (i = dev->real_num_rx_queues - 1; i >= 0; i--)
+		if (dev->_rx[i].mp_params.mp_priv)
+			/* The channel count is the idx plus 1. */
+			return i + 1;
+
+	return 0;
 }
 
 /**
···
 		dev_tcx_uninstall(dev);
 		dev_xdp_uninstall(dev);
 		bpf_dev_bound_netdev_unregister(dev);
+		dev_dmabuf_uninstall(dev);
 
 		netdev_offload_xstats_disable_all(dev);
 

net/core/devmem.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *      Devmem TCP
+ *
+ *      Authors:	Mina Almasry <[e-mail]>
+ *			Willem de Bruijn <[e-mail]>
+ *			Kaiyuan Zhang <[e-mail]
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/genalloc.h>
+#include <linux/mm.h>
+#include <linux/netdevice.h>
+#include <linux/types.h>
+#include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
+#include <net/page_pool/helpers.h>
+#include <trace/events/page_pool.h>
+
+#include "devmem.h"
+#include "mp_dmabuf_devmem.h"
+#include "page_pool_priv.h"
+
+/* Device memory support */
+
+/* Protected by rtnl_lock() */
+static DEFINE_XARRAY_FLAGS(net_devmem_dmabuf_bindings, XA_FLAGS_ALLOC1);
+
+static void net_devmem_dmabuf_free_chunk_owner(struct gen_pool *genpool,
+					       struct gen_pool_chunk *chunk,
+					       void *not_used)
+{
+	struct dmabuf_genpool_chunk_owner *owner = chunk->owner;
+
+	kvfree(owner->niovs);
+	kfree(owner);
+}
+
+static dma_addr_t net_devmem_get_dma_addr(const struct net_iov *niov)
+{
+	struct dmabuf_genpool_chunk_owner *owner = net_iov_owner(niov);
+
+	return owner->base_dma_addr +
+	       ((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
+}
+
+void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
+{
+	size_t size, avail;
+
+	gen_pool_for_each_chunk(binding->chunk_pool,
+				net_devmem_dmabuf_free_chunk_owner, NULL);
+
+	size = gen_pool_size(binding->chunk_pool);
+	avail = gen_pool_avail(binding->chunk_pool);
+
+	if (!WARN(size != avail, "can't destroy genpool. size=%zu, avail=%zu",
+		  size, avail))
+		gen_pool_destroy(binding->chunk_pool);
+
+	dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
+					  DMA_FROM_DEVICE);
+	dma_buf_detach(binding->dmabuf, binding->attachment);
+	dma_buf_put(binding->dmabuf);
+	xa_destroy(&binding->bound_rxqs);
+	kfree(binding);
+}
+
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+	struct dmabuf_genpool_chunk_owner *owner;
+	unsigned long dma_addr;
+	struct net_iov *niov;
+	ssize_t offset;
+	ssize_t index;
+
+	dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE,
+					(void **)&owner);
+	if (!dma_addr)
+		return NULL;
+
+	offset = dma_addr - owner->base_dma_addr;
+	index = offset / PAGE_SIZE;
+	niov = &owner->niovs[index];
+
+	niov->pp_magic = 0;
+	niov->pp = NULL;
+	atomic_long_set(&niov->pp_ref_count, 0);
+
+	return niov;
+}
+
+void net_devmem_free_dmabuf(struct net_iov *niov)
+{
+	struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
+	unsigned long dma_addr = net_devmem_get_dma_addr(niov);
+
+	if (WARN_ON(!gen_pool_has_addr(binding->chunk_pool, dma_addr,
+				       PAGE_SIZE)))
+		return;
+
+	gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
+}
+
+void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+	struct netdev_rx_queue *rxq;
+	unsigned long xa_idx;
+	unsigned int rxq_idx;
+
+	if (binding->list.next)
+		list_del(&binding->list);
+
+	xa_for_each(&binding->bound_rxqs, xa_idx, rxq) {
+		WARN_ON(rxq->mp_params.mp_priv != binding);
+
+		rxq->mp_params.mp_priv = NULL;
+
+		rxq_idx = get_netdev_rx_queue_index(rxq);
+
+		WARN_ON(netdev_rx_queue_restart(binding->dev, rxq_idx));
+	}
+
+	xa_erase(&net_devmem_dmabuf_bindings, binding->id);
+
+	net_devmem_dmabuf_binding_put(binding);
+}
+
+int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
+				    struct net_devmem_dmabuf_binding *binding,
+				    struct netlink_ext_ack *extack)
+{
+	struct netdev_rx_queue *rxq;
+	u32 xa_idx;
+	int err;
+
+	if (rxq_idx >= dev->real_num_rx_queues) {
+		NL_SET_ERR_MSG(extack, "rx queue index out of range");
+		return -ERANGE;
+	}
+
+	rxq = __netif_get_rx_queue(dev, rxq_idx);
+	if (rxq->mp_params.mp_priv) {
+		NL_SET_ERR_MSG(extack, "designated queue already memory provider bound");
+		return -EEXIST;
+	}
+
+#ifdef CONFIG_XDP_SOCKETS
+	if (rxq->pool) {
+		NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
+		return -EBUSY;
+	}
+#endif
+
+	err = xa_alloc(&binding->bound_rxqs, &xa_idx, rxq, xa_limit_32b,
+		       GFP_KERNEL);
+	if (err)
+		return err;
+
+	rxq->mp_params.mp_priv = binding;
+
+	err = netdev_rx_queue_restart(dev, rxq_idx);
+	if (err)
+		goto err_xa_erase;
+
+	return 0;
+
+err_xa_erase:
+	rxq->mp_params.mp_priv = NULL;
+	xa_erase(&binding->bound_rxqs, xa_idx);
+
+	return err;
+}
+
+struct net_devmem_dmabuf_binding *
+net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
+		       struct netlink_ext_ack *extack)
+{
+	struct net_devmem_dmabuf_binding *binding;
+	static u32 id_alloc_next;
+	struct scatterlist *sg;
+	struct dma_buf *dmabuf;
+	unsigned int sg_idx, i;
+	unsigned long virtual;
+	int err;
+
+	dmabuf = dma_buf_get(dmabuf_fd);
+	if (IS_ERR(dmabuf))
+		return ERR_CAST(dmabuf);
+
+	binding = kzalloc_node(sizeof(*binding), GFP_KERNEL,
+			       dev_to_node(&dev->dev));
+	if (!binding) {
+		err = -ENOMEM;
+		goto err_put_dmabuf;
+	}
+
+	binding->dev = dev;
+
+	err = xa_alloc_cyclic(&net_devmem_dmabuf_bindings, &binding->id,
+			      binding, xa_limit_32b, &id_alloc_next,
+			      GFP_KERNEL);
+	if (err < 0)
+		goto err_free_binding;
+
+	xa_init_flags(&binding->bound_rxqs, XA_FLAGS_ALLOC);
+
+	refcount_set(&binding->ref, 1);
+
+	binding->dmabuf = dmabuf;
+
+	binding->attachment = dma_buf_attach(binding->dmabuf, dev->dev.parent);
+	if (IS_ERR(binding->attachment)) {
+		err = PTR_ERR(binding->attachment);
+		NL_SET_ERR_MSG(extack, "Failed to bind dmabuf to device");
+		goto err_free_id;
+	}
+
+	binding->sgt = dma_buf_map_attachment_unlocked(binding->attachment,
+						       DMA_FROM_DEVICE);
+	if (IS_ERR(binding->sgt)) {
+		err = PTR_ERR(binding->sgt);
+		NL_SET_ERR_MSG(extack, "Failed to map dmabuf attachment");
+		goto err_detach;
+	}
+
+	/* For simplicity we expect to make PAGE_SIZE allocations, but the
+	 * binding can be much more flexible than that. We may be able to
+	 * allocate MTU sized chunks here. Leave that for future work...
+	 */
+	binding->chunk_pool =
+		gen_pool_create(PAGE_SHIFT, dev_to_node(&dev->dev));
+	if (!binding->chunk_pool) {
+		err = -ENOMEM;
+		goto err_unmap;
+	}
+
+	virtual = 0;
+	for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx) {
+		dma_addr_t dma_addr = sg_dma_address(sg);
+		struct dmabuf_genpool_chunk_owner *owner;
+		size_t len = sg_dma_len(sg);
+		struct net_iov *niov;
+
+		owner = kzalloc_node(sizeof(*owner), GFP_KERNEL,
+				     dev_to_node(&dev->dev));
+		if (!owner) {
+			err = -ENOMEM;
+			goto err_free_chunks;
+		}
+
+		owner->base_virtual = virtual;
+		owner->base_dma_addr = dma_addr;
+		owner->num_niovs = len / PAGE_SIZE;
+		owner->binding = binding;
+
+		err = gen_pool_add_owner(binding->chunk_pool, dma_addr,
+					 dma_addr, len, dev_to_node(&dev->dev),
+					 owner);
+		if (err) {
+			kfree(owner);
+			err = -EINVAL;
+			goto err_free_chunks;
+		}
+
+		owner->niovs = kvmalloc_array(owner->num_niovs,
+					      sizeof(*owner->niovs),
+					      GFP_KERNEL);
+		if (!owner->niovs) {
+			err = -ENOMEM;
+			goto err_free_chunks;
+		}
+
+		for (i = 0; i < owner->num_niovs; i++) {
+			niov = &owner->niovs[i];
+			niov->owner = owner;
+			page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
+						      net_devmem_get_dma_addr(niov));
+		}
+
+		virtual += len;
+	}
+
+	return binding;
+
+err_free_chunks:
+	gen_pool_for_each_chunk(binding->chunk_pool,
+				net_devmem_dmabuf_free_chunk_owner, NULL);
+	gen_pool_destroy(binding->chunk_pool);
+err_unmap:
+	dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
+					  DMA_FROM_DEVICE);
+err_detach:
+	dma_buf_detach(dmabuf, binding->attachment);
+err_free_id:
+	xa_erase(&net_devmem_dmabuf_bindings, binding->id);
+err_free_binding:
+	kfree(binding);
+err_put_dmabuf:
+	dma_buf_put(dmabuf);
+	return ERR_PTR(err);
+}
+
+void dev_dmabuf_uninstall(struct net_device *dev)
+{
+	struct net_devmem_dmabuf_binding *binding;
+	struct netdev_rx_queue *rxq;
+	unsigned long xa_idx;
+	unsigned int i;
+
+	for (i = 0; i < dev->real_num_rx_queues; i++) {
+		binding = dev->_rx[i].mp_params.mp_priv;
+		if (!binding)
+			continue;
+
+		xa_for_each(&binding->bound_rxqs, xa_idx, rxq)
+			if (rxq == &dev->_rx[i]) {
+				xa_erase(&binding->bound_rxqs, xa_idx);
+				break;
+			}
+	}
+}
+
+/*** "Dmabuf devmem memory provider" ***/
+
+int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+	if (!binding)
+		return -EINVAL;
+
+	if (!pool->dma_map)
+		return -EOPNOTSUPP;
+
+	if (pool->dma_sync)
+		return -EOPNOTSUPP;
+
+	if (pool->p.order != 0)
+		return -E2BIG;
+
+	net_devmem_dmabuf_binding_get(binding);
+	return 0;
+}
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+	struct net_iov *niov;
+	netmem_ref netmem;
+
+	niov = net_devmem_alloc_dmabuf(binding);
+	if (!niov)
+		return 0;
+
+	netmem = net_iov_to_netmem(niov);
+
+	page_pool_set_pp_info(pool, netmem);
+
+	pool->pages_state_hold_cnt++;
+	trace_page_pool_state_hold(pool, netmem, pool->pages_state_hold_cnt);
+	return netmem;
+}
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
+
+	net_devmem_dmabuf_binding_put(binding);
+}
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem)
+{
+	long refcount = atomic_long_read(netmem_get_pp_ref_count_ref(netmem));
+
+	if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))
+		return false;
+
+	if (WARN_ON_ONCE(refcount != 1))
+		return false;
+
+	page_pool_clear_pp_info(netmem);
+
+	net_devmem_free_dmabuf(netmem_to_net_iov(netmem));
+
+	/* We don't want the page pool put_page()ing our net_iovs. */
+	return false;
+}

net/core/devmem.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Device memory TCP support
+ *
+ * Authors:	Mina Almasry <[e-mail]>
+ *		Willem de Bruijn <[e-mail]>
+ *		Kaiyuan Zhang <[e-mail]>
+ *
+ */
+#ifndef _NET_DEVMEM_H
+#define _NET_DEVMEM_H
+
+struct netlink_ext_ack;
+
+struct net_devmem_dmabuf_binding {
+	struct dma_buf *dmabuf;
+	struct dma_buf_attachment *attachment;
+	struct sg_table *sgt;
+	struct net_device *dev;
+	struct gen_pool *chunk_pool;
+
+	/* The user holds a ref (via the netlink API) for as long as they want
+	 * the binding to remain alive. Each page pool using this binding holds
+	 * a ref to keep the binding alive. Each allocated net_iov holds a
+	 * ref.
+	 *
+	 * The binding undos itself and unmaps the underlying dmabuf once all
+	 * those refs are dropped and the binding is no longer desired or in
+	 * use.
+	 */
+	refcount_t ref;
+
+	/* The list of bindings currently active. Used for netlink to notify us
+	 * of the user dropping the bind.
+	 */
+	struct list_head list;
+
+	/* rxq's this binding is active on. */
+	struct xarray bound_rxqs;
+
+	/* ID of this binding. Globally unique to all bindings currently
+	 * active.
+	 */
+	u32 id;
+};
+
+#if defined(CONFIG_NET_DEVMEM)
+/* Owner of the dma-buf chunks inserted into the gen pool. Each scatterlist
+ * entry from the dmabuf is inserted into the genpool as a chunk, and needs
+ * this owner struct to keep track of some metadata necessary to create
+ * allocations from this chunk.
+ */
+struct dmabuf_genpool_chunk_owner {
+	/* Offset into the dma-buf where this chunk starts.  */
+	unsigned long base_virtual;
+
+	/* dma_addr of the start of the chunk.  */
+	dma_addr_t base_dma_addr;
+
+	/* Array of net_iovs for this chunk. */
+	struct net_iov *niovs;
+	size_t num_niovs;
+
+	struct net_devmem_dmabuf_binding *binding;
+};
+
+void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding);
+struct net_devmem_dmabuf_binding *
+net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
+		       struct netlink_ext_ack *extack);
+void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
+int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
+				    struct net_devmem_dmabuf_binding *binding,
+				    struct netlink_ext_ack *extack);
+void dev_dmabuf_uninstall(struct net_device *dev);
+
+static inline struct dmabuf_genpool_chunk_owner *
+net_iov_owner(const struct net_iov *niov)
+{
+	return niov->owner;
+}
+
+static inline unsigned int net_iov_idx(const struct net_iov *niov)
+{
+	return niov - net_iov_owner(niov)->niovs;
+}
+
+static inline struct net_devmem_dmabuf_binding *
+net_iov_binding(const struct net_iov *niov)
+{
+	return net_iov_owner(niov)->binding;
+}
+
+static inline unsigned long net_iov_virtual_addr(const struct net_iov *niov)
+{
+	struct dmabuf_genpool_chunk_owner *owner = net_iov_owner(niov);
+
+	return owner->base_virtual +
+	       ((unsigned long)net_iov_idx(niov) << PAGE_SHIFT);
+}
+
+static inline u32 net_iov_binding_id(const struct net_iov *niov)
+{
+	return net_iov_owner(niov)->binding->id;
+}
+
+static inline void
+net_devmem_dmabuf_binding_get(struct net_devmem_dmabuf_binding *binding)
+{
+	refcount_inc(&binding->ref);
+}
+
+static inline void
+net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)
+{
+	if (!refcount_dec_and_test(&binding->ref))
+		return;
+
+	__net_devmem_dmabuf_binding_free(binding);
+}
+
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
+void net_devmem_free_dmabuf(struct net_iov *ppiov);
+
+#else
+struct net_devmem_dmabuf_binding;
+
+static inline void
+__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
+{
+}
+
+static inline struct net_devmem_dmabuf_binding *
+net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
+		       struct netlink_ext_ack *extack)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void
+net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+}
+
+static inline int
+net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
+				struct net_devmem_dmabuf_binding *binding,
+				struct netlink_ext_ack *extack)
+
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void dev_dmabuf_uninstall(struct net_device *dev)
+{
+}
+
+static inline struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+	return NULL;
+}
+
+static inline void net_devmem_free_dmabuf(struct net_iov *ppiov)
+{
+}
+
+static inline unsigned long net_iov_virtual_addr(const struct net_iov *niov)
+{
+	return 0;
+}
+
+static inline u32 net_iov_binding_id(const struct net_iov *niov)
+{
+	return 0;
+}
+#endif
+
+#endif /* _NET_DEVMEM_H */

net/core/gro.c

···
 	pinfo = skb_shinfo(skb);
 	frag0 = &pinfo->frags[0];
 
-	if (pinfo->nr_frags && !PageHighMem(skb_frag_page(frag0)) &&
+	if (pinfo->nr_frags && skb_frag_page(frag0) &&
+	    !PageHighMem(skb_frag_page(frag0)) &&
 	    (!NET_IP_ALIGN || !((skb_frag_off(frag0) + nhoff) & 3))) {
 		NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0);
 		NAPI_GRO_CB(skb)->frag0_len = min_t(unsigned int,

net/core/mp_dmabuf_devmem.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Dmabuf device memory provider.
+ *
+ * Authors:	Mina Almasry <[e-mail]>
+ *
+ */
+#ifndef _NET_MP_DMABUF_DEVMEM_H
+#define _NET_MP_DMABUF_DEVMEM_H
+
+#include <net/netmem.h>
+
+#if defined(CONFIG_NET_DEVMEM)
+int mp_dmabuf_devmem_init(struct page_pool *pool);
+
+netmem_ref mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp);
+
+void mp_dmabuf_devmem_destroy(struct page_pool *pool);
+
+bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem);
+#else
+static inline int mp_dmabuf_devmem_init(struct page_pool *pool)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline netmem_ref
+mp_dmabuf_devmem_alloc_netmems(struct page_pool *pool, gfp_t gfp)
+{
+	return 0;
+}
+
+static inline void mp_dmabuf_devmem_destroy(struct page_pool *pool)
+{
+}
+
+static inline bool
+mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem)
+{
+	return false;
+}
+#endif
+
+#endif /* _NET_MP_DMABUF_DEVMEM_H */

net/core/netdev-genl-gen.c

···
 #include "netdev-genl-gen.h"
 
 #include <uapi/linux/netdev.h>
+#include <linux/list.h>
 
 /* Integer value ranges */
 static const struct netlink_range_validation netdev_a_page_pool_id_range = {
···
 const struct nla_policy netdev_page_pool_info_nl_policy[NETDEV_A_PAGE_POOL_IFINDEX + 1] = {
 	[NETDEV_A_PAGE_POOL_ID] = NLA_POLICY_FULL_RANGE(NLA_UINT, &netdev_a_page_pool_id_range),
 	[NETDEV_A_PAGE_POOL_IFINDEX] = NLA_POLICY_FULL_RANGE(NLA_U32, &netdev_a_page_pool_ifindex_range),
+};
+
+const struct nla_policy netdev_queue_id_nl_policy[NETDEV_A_QUEUE_TYPE + 1] = {
+	[NETDEV_A_QUEUE_ID] = { .type = NLA_U32, },
+	[NETDEV_A_QUEUE_TYPE] = NLA_POLICY_MAX(NLA_U32, 1),
 };
 
 /* NETDEV_CMD_DEV_GET - do */
···
 static const struct nla_policy netdev_qstats_get_nl_policy[NETDEV_A_QSTATS_SCOPE + 1] = {
 	[NETDEV_A_QSTATS_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
 	[NETDEV_A_QSTATS_SCOPE] = NLA_POLICY_MASK(NLA_UINT, 0x1),
+};
+
+/* NETDEV_CMD_BIND_RX - do */
+static const struct nla_policy netdev_bind_rx_nl_policy[NETDEV_A_DMABUF_FD + 1] = {
+	[NETDEV_A_DMABUF_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
+	[NETDEV_A_DMABUF_FD] = { .type = NLA_U32, },
+	[NETDEV_A_DMABUF_QUEUES] = NLA_POLICY_NESTED(netdev_queue_id_nl_policy),
 };
 
 /* Ops table for netdev */
···
 		.maxattr	= NETDEV_A_QSTATS_SCOPE,
 		.flags		= GENL_CMD_CAP_DUMP,
 	},
+	{
+		.cmd		= NETDEV_CMD_BIND_RX,
+		.doit		= netdev_nl_bind_rx_doit,
+		.policy		= netdev_bind_rx_nl_policy,
+		.maxattr	= NETDEV_A_DMABUF_FD,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group netdev_nl_mcgrps[] = {
···
 	.n_split_ops	= ARRAY_SIZE(netdev_nl_ops),
 	.mcgrps		= netdev_nl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(netdev_nl_mcgrps),
+	.sock_priv_size	= sizeof(struct list_head),
+	.sock_priv_init	= (void *)netdev_nl_sock_priv_init,
+	.sock_priv_destroy = (void *)netdev_nl_sock_priv_destroy,
 };

net/core/netdev-genl-gen.h

···
 #include <net/genetlink.h>
 
 #include <uapi/linux/netdev.h>
+#include <linux/list.h>
 
 /* Common nested types */
 extern const struct nla_policy netdev_page_pool_info_nl_policy[NETDEV_A_PAGE_POOL_IFINDEX + 1];
+extern const struct nla_policy netdev_queue_id_nl_policy[NETDEV_A_QUEUE_TYPE + 1];
 
 int netdev_nl_dev_get_doit(struct sk_buff *skb, struct genl_info *info);
 int netdev_nl_dev_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
···
 int netdev_nl_napi_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 				struct netlink_callback *cb);
+int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	NETDEV_NLGRP_MGMT,
···
 };
 
 extern struct genl_family netdev_nl_family;
+
+void netdev_nl_sock_priv_init(struct list_head *priv);
+void netdev_nl_sock_priv_destroy(struct list_head *priv);
 
 #endif /* _LINUX_NETDEV_GEN_H */

net/core/netdev-genl.c

···
 #include <linux/netdevice.h>
 #include <linux/notifier.h>
 #include <linux/rtnetlink.h>
+#include <net/busy_poll.h>
 #include <net/net_namespace.h>
+#include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
 #include <net/sock.h>
 #include <net/xdp.h>
 #include <net/xdp_sock.h>
-#include <net/netdev_rx_queue.h>
-#include <net/netdev_queues.h>
-#include <net/busy_poll.h>
 
-#include "netdev-genl-gen.h"
 #include "dev.h"
+#include "devmem.h"
+#include "netdev-genl-gen.h"
 
 struct netdev_nl_dump_ctx {
 	unsigned long	ifindex;
···
 netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
 			 u32 q_idx, u32 q_type, const struct genl_info *info)
 {
+	struct net_devmem_dmabuf_binding *binding;
 	struct netdev_rx_queue *rxq;
 	struct netdev_queue *txq;
 	void *hdr;
···
 		if (rxq->napi && nla_put_u32(rsp, NETDEV_A_QUEUE_NAPI_ID,
 					     rxq->napi->napi_id))
 			goto nla_put_failure;
+
+		binding = rxq->mp_params.mp_priv;
+		if (binding &&
+		    nla_put_u32(rsp, NETDEV_A_QUEUE_DMABUF, binding->id))
+			goto nla_put_failure;
+
 		break;
 	case NETDEV_QUEUE_TYPE_TX:
 		txq = netdev_get_tx_queue(netdev, q_idx);
···
 	rtnl_unlock();
 
 	return err;
+}
+
+int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *tb[ARRAY_SIZE(netdev_queue_id_nl_policy)];
+	struct net_devmem_dmabuf_binding *binding;
+	struct list_head *sock_binding_list;
+	u32 ifindex, dmabuf_fd, rxq_idx;
+	struct net_device *netdev;
+	struct sk_buff *rsp;
+	struct nlattr *attr;
+	int rem, err = 0;
+	void *hdr;
+
+	if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_DEV_IFINDEX) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_DMABUF_FD) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_DMABUF_QUEUES))
+		return -EINVAL;
+
+	ifindex = nla_get_u32(info->attrs[NETDEV_A_DEV_IFINDEX]);
+	dmabuf_fd = nla_get_u32(info->attrs[NETDEV_A_DMABUF_FD]);
+
+	sock_binding_list = genl_sk_priv_get(&netdev_nl_family,
+					     NETLINK_CB(skb).sk);
+	if (IS_ERR(sock_binding_list))
+		return PTR_ERR(sock_binding_list);
+
+	rsp = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!rsp)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(rsp, info);
+	if (!hdr) {
+		err = -EMSGSIZE;
+		goto err_genlmsg_free;
+	}
+
+	rtnl_lock();
+
+	netdev = __dev_get_by_index(genl_info_net(info), ifindex);
+	if (!netdev || !netif_device_present(netdev)) {
+		err = -ENODEV;
+		goto err_unlock;
+	}
+
+	if (dev_xdp_prog_count(netdev)) {
+		NL_SET_ERR_MSG(info->extack, "unable to bind dmabuf to device with XDP program attached");
+		err = -EEXIST;
+		goto err_unlock;
+	}
+
+	binding = net_devmem_bind_dmabuf(netdev, dmabuf_fd, info->extack);
+	if (IS_ERR(binding)) {
+		err = PTR_ERR(binding);
+		goto err_unlock;
+	}
+
+	nla_for_each_attr_type(attr, NETDEV_A_DMABUF_QUEUES,
+			       genlmsg_data(info->genlhdr),
+			       genlmsg_len(info->genlhdr), rem) {
+		err = nla_parse_nested(
+			tb, ARRAY_SIZE(netdev_queue_id_nl_policy) - 1, attr,
+			netdev_queue_id_nl_policy, info->extack);
+		if (err < 0)
+			goto err_unbind;
+
+		if (NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_ID) ||
+		    NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_TYPE)) {
+			err = -EINVAL;
+			goto err_unbind;
+		}
+
+		if (nla_get_u32(tb[NETDEV_A_QUEUE_TYPE]) != NETDEV_QUEUE_TYPE_RX) {
+			NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_TYPE]);
+			err = -EINVAL;
+			goto err_unbind;
+		}
+
+		rxq_idx = nla_get_u32(tb[NETDEV_A_QUEUE_ID]);
+
+		err = net_devmem_bind_dmabuf_to_queue(netdev, rxq_idx, binding,
+						      info->extack);
+		if (err)
+			goto err_unbind;
+	}
+
+	list_add(&binding->list, sock_binding_list);
+
+	nla_put_u32(rsp, NETDEV_A_DMABUF_ID, binding->id);
+	genlmsg_end(rsp, hdr);
+
+	err = genlmsg_reply(rsp, info);
+	if (err)
+		goto err_unbind;
+
+	rtnl_unlock();
+
+	return 0;
+
+err_unbind:
+	net_devmem_unbind_dmabuf(binding);
+err_unlock:
+	rtnl_unlock();
+err_genlmsg_free:
+	nlmsg_free(rsp);
+	return err;
+}
+
+void netdev_nl_sock_priv_init(struct list_head *priv)
+{
+	INIT_LIST_HEAD(priv);
+}
+
+void netdev_nl_sock_priv_destroy(struct list_head *priv)
+{
+	struct net_devmem_dmabuf_binding *binding;
+	struct net_devmem_dmabuf_binding *temp;
+
+	list_for_each_entry_safe(binding, temp, priv, list) {
+		rtnl_lock();
+		net_devmem_unbind_dmabuf(binding);
+		rtnl_unlock();
+	}
 }
 
 static int netdev_genl_netdevice_event(struct notifier_block *nb,

net/core/netdev_rx_queue.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/netdevice.h>
+#include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
+
+#include "page_pool_priv.h"
+
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
+{
+	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
+	void *new_mem, *old_mem;
+	int err;
+
+	if (!dev->queue_mgmt_ops || !dev->queue_mgmt_ops->ndo_queue_stop ||
+	    !dev->queue_mgmt_ops->ndo_queue_mem_free ||
+	    !dev->queue_mgmt_ops->ndo_queue_mem_alloc ||
+	    !dev->queue_mgmt_ops->ndo_queue_start)
+		return -EOPNOTSUPP;
+
+	ASSERT_RTNL();
+
+	new_mem = kvzalloc(dev->queue_mgmt_ops->ndo_queue_mem_size, GFP_KERNEL);
+	if (!new_mem)
+		return -ENOMEM;
+
+	old_mem = kvzalloc(dev->queue_mgmt_ops->ndo_queue_mem_size, GFP_KERNEL);
+	if (!old_mem) {
+		err = -ENOMEM;
+		goto err_free_new_mem;
+	}
+
+	err = dev->queue_mgmt_ops->ndo_queue_mem_alloc(dev, new_mem, rxq_idx);
+	if (err)
+		goto err_free_old_mem;
+
+	err = page_pool_check_memory_provider(dev, rxq);
+	if (err)
+		goto err_free_new_queue_mem;
+
+	err = dev->queue_mgmt_ops->ndo_queue_stop(dev, old_mem, rxq_idx);
+	if (err)
+		goto err_free_new_queue_mem;
+
+	err = dev->queue_mgmt_ops->ndo_queue_start(dev, new_mem, rxq_idx);
+	if (err)
+		goto err_start_queue;
+
+	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+
+	kvfree(old_mem);
+	kvfree(new_mem);
+
+	return 0;
+
+err_start_queue:
+	/* Restarting the queue with old_mem should be successful as we haven't
+	 * changed any of the queue configuration, and there is not much we can
+	 * do to recover from a failure here.
+	 *
+	 * WARN if we fail to recover the old rx queue, and at least free
+	 * old_mem so we don't also leak that.
+	 */
+	if (dev->queue_mgmt_ops->ndo_queue_start(dev, old_mem, rxq_idx)) {
+		WARN(1,
+		     "Failed to restart old queue in error path. RX queue %d may be unhealthy.",
+		     rxq_idx);
+		dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+	}
+
+err_free_new_queue_mem:
+	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, new_mem);
+
+err_free_old_mem:
+	kvfree(old_mem);
+
+err_free_new_mem:
+	kvfree(new_mem);
+
+	return err;
+}

net/core/netmem_priv.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __NETMEM_PRIV_H
+#define __NETMEM_PRIV_H
+
+static inline unsigned long netmem_get_pp_magic(netmem_ref netmem)
+{
+	return __netmem_clear_lsb(netmem)->pp_magic;
+}
+
+static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long pp_magic)
+{
+	__netmem_clear_lsb(netmem)->pp_magic |= pp_magic;
+}
+
+static inline void netmem_clear_pp_magic(netmem_ref netmem)
+{
+	__netmem_clear_lsb(netmem)->pp_magic = 0;
+}
+
+static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool)
+{
+	__netmem_clear_lsb(netmem)->pp = pool;
+}
+
+static inline void netmem_set_dma_addr(netmem_ref netmem,
+				       unsigned long dma_addr)
+{
+	__netmem_clear_lsb(netmem)->dma_addr = dma_addr;
+}
+#endif

net/core/page_pool.c

···
 #include <linux/slab.h>
 #include <linux/device.h>
 
+#include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>
 #include <net/xdp.h>
 
···
 
 #include <trace/events/page_pool.h>
 
+#include "mp_dmabuf_devmem.h"
+#include "netmem_priv.h"
 #include "page_pool_priv.h"
+
+DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
 
 #define DEFER_TIME (msecs_to_jiffies(1000))
 #define DEFER_WARN_INTERVAL (60 * HZ)
···
 			  int cpuid)
 {
 	unsigned int ring_qsize = 1024; /* Default */
+	struct netdev_rx_queue *rxq;
+	int err;
 
 	page_pool_struct_check();
 
···
 	if (pool->dma_map)
 		get_device(pool->p.dev);
 
+	if (pool->slow.flags & PP_FLAG_ALLOW_UNREADABLE_NETMEM) {
+		/* We rely on rtnl_lock()ing to make sure netdev_rx_queue
+		 * configuration doesn't change while we're initializing
+		 * the page_pool.
+		 */
+		ASSERT_RTNL();
+		rxq = __netif_get_rx_queue(pool->slow.netdev,
+					   pool->slow.queue_idx);
+		pool->mp_priv = rxq->mp_params.mp_priv;
+	}
+
+	if (pool->mp_priv) {
+		err = mp_dmabuf_devmem_init(pool);
+		if (err) {
+			pr_warn("%s() mem-provider init failed %d\n", __func__,
+				err);
+			goto free_ptr_ring;
+		}
+
+		static_branch_inc(&page_pool_mem_providers);
+	}
+
 	return 0;
+
+free_ptr_ring:
+	ptr_ring_cleanup(&pool->ring, NULL);
+#ifdef CONFIG_PAGE_POOL_STATS
+	if (!pool->system)
+		free_percpu(pool->recycle_stats);
+#endif
+	return err;
 }
 
 static void page_pool_uninit(struct page_pool *pool)
···
 		if (unlikely(!netmem))
 			break;
 
-		if (likely(page_to_nid(netmem_to_page(netmem)) == pref_nid)) {
+		if (likely(netmem_is_pref_nid(netmem, pref_nid))) {
 			pool->alloc.cache[pool->alloc.count++] = netmem;
 		} else {
 			/* NUMA mismatch;
···
 			     PAGE_SIZE << pool->p.order, pool->p.dma_dir,
 			     DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
 	return false;
-}
-
-static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
-{
-	struct page *page = netmem_to_page(netmem);
-
-	page->pp = pool;
-	page->pp_magic |= PP_SIGNATURE;
-
-	/* Ensuring all pages have been split into one fragment initially:
-	 * page_pool_set_pp_info() is only called once for every page when it
-	 * is allocated from the page allocator and page_pool_fragment_page()
-	 * is dirtying the same cache line as the page->pp_magic above, so
-	 * the overhead is negligible.
-	 */
-	page_pool_fragment_netmem(netmem, 1);
-	if (pool->has_init_callback)
-		pool->slow.init_callback(netmem, pool->slow.init_arg);
-}
-
-static void page_pool_clear_pp_info(netmem_ref netmem)
-{
-	struct page *page = netmem_to_page(netmem);
-
-	page->pp_magic = 0;
-	page->pp = NULL;
 }
 
 static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
···
 		return netmem;
 
 	/* Slow-path: cache empty, do real allocation */
-	netmem = __page_pool_alloc_pages_slow(pool, gfp);
+	if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_priv)
+		netmem = mp_dmabuf_devmem_alloc_netmems(pool, gfp);
+	else
+		netmem = __page_pool_alloc_pages_slow(pool, gfp);
 	return netmem;
 }
 EXPORT_SYMBOL(page_pool_alloc_netmem);
···
 	return inflight;
 }
 
+void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
+{
+	netmem_set_pp(netmem, pool);
+	netmem_or_pp_magic(netmem, PP_SIGNATURE);
+
+	/* Ensuring all pages have been split into one fragment initially:
+	 * page_pool_set_pp_info() is only called once for every page when it
+	 * is allocated from the page allocator and page_pool_fragment_page()
+	 * is dirtying the same cache line as the page->pp_magic above, so
+	 * the overhead is negligible.
+	 */
+	page_pool_fragment_netmem(netmem, 1);
+	if (pool->has_init_callback)
+		pool->slow.init_callback(netmem, pool->slow.init_arg);
+}
+
+void page_pool_clear_pp_info(netmem_ref netmem)
+{
+	netmem_clear_pp_magic(netmem);
+	netmem_set_pp(netmem, NULL);
+}
+
 static __always_inline void __page_pool_release_page_dma(struct page_pool *pool,
 							 netmem_ref netmem)
 {
···
 void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
 {
 	int count;
+	bool put;
 
-	__page_pool_release_page_dma(pool, netmem);
+	put = true;
+	if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_priv)
+		put = mp_dmabuf_devmem_release_page(pool, netmem);
+	else
+		__page_pool_release_page_dma(pool, netmem);
 
 	/* This may be the last page returned, releasing the pool, so
 	 * it is not safe to reference pool afterwards.
···
 	count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
 	trace_page_pool_state_release(pool, netmem, count);
 
-	page_pool_clear_pp_info(netmem);
-	put_page(netmem_to_page(netmem));
+	if (put) {
+		page_pool_clear_pp_info(netmem);
+		put_page(netmem_to_page(netmem));
+	}
 	/* An optimization would be to call __free_pages(page, pool->p.order)
 	 * knowing page is not part of page-cache (thus avoiding a
 	 * __page_cache_release() call).
···
 
 static bool __page_pool_page_can_be_recycled(netmem_ref netmem)
 {
-	return page_ref_count(netmem_to_page(netmem)) == 1 &&
-	       !page_is_pfmemalloc(netmem_to_page(netmem));
+	return netmem_is_net_iov(netmem) ||
+	       (page_ref_count(netmem_to_page(netmem)) == 1 &&
+		!page_is_pfmemalloc(netmem_to_page(netmem)));
 }
 
 /* If the page refcnt == 1, this will try to recycle the page.
···
 		/* Page found as candidate for recycling */
 		return netmem;
 	}
+
 	/* Fallback/non-XDP mode: API user have elevated refcnt.
 	 *
 	 * Many drivers split up the page into fragments, and some
···
 	/* Empty recycle ring */
 	while ((netmem = (__force netmem_ref)ptr_ring_consume_bh(&pool->ring))) {
 		/* Verify the refcnt invariant of cached pages */
-		if (!(page_ref_count(netmem_to_page(netmem)) == 1))
+		if (!(netmem_ref_count(netmem) == 1))
 			pr_crit("%s() page_pool refcnt %d violation\n",
 				__func__, netmem_ref_count(netmem));
 
···
 
 	page_pool_unlist(pool);
 	page_pool_uninit(pool);
+
+	if (pool->mp_priv) {
+		mp_dmabuf_devmem_destroy(pool);
+		static_branch_dec(&page_pool_mem_providers);
+	}
+
 	kfree(pool);
 }
 

net/core/page_pool_priv.h

···
 #ifndef __PAGE_POOL_PRIV_H
 #define __PAGE_POOL_PRIV_H
 
+#include <net/page_pool/helpers.h>
+
+#include "netmem_priv.h"
+
 s32 page_pool_inflight(const struct page_pool *pool, bool strict);
 
 int page_pool_list(struct page_pool *pool);
 void page_pool_detached(struct page_pool *pool);
 void page_pool_unlist(struct page_pool *pool);
+
+static inline bool
+page_pool_set_dma_addr_netmem(netmem_ref netmem, dma_addr_t addr)
+{
+	if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
+		netmem_set_dma_addr(netmem, addr >> PAGE_SHIFT);
+
+		/* We assume page alignment to shave off bottom bits,
+		 * if this "compression" doesn't work we need to drop.
+		 */
+		return addr != (dma_addr_t)netmem_get_dma_addr(netmem)
+				       << PAGE_SHIFT;
+	}
+
+	netmem_set_dma_addr(netmem, addr);
+	return false;
+}
+
+static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
+{
+	return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
+}
+
+#if defined(CONFIG_PAGE_POOL)
+void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem);
+void page_pool_clear_pp_info(netmem_ref netmem);
+int page_pool_check_memory_provider(struct net_device *dev,
+				    struct netdev_rx_queue *rxq);
+#else
+static inline void page_pool_set_pp_info(struct page_pool *pool,
+					 netmem_ref netmem)
+{
+}
+static inline void page_pool_clear_pp_info(netmem_ref netmem)
+{
+}
+static inline int page_pool_check_memory_provider(struct net_device *dev,
+						  struct netdev_rx_queue *rxq)
+{
+	return 0;
+}
+#endif
 
 #endif

net/core/page_pool_user.c

···
 #include <linux/netdevice.h>
 #include <linux/xarray.h>
 #include <net/net_debug.h>
-#include <net/page_pool/types.h>
+#include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>
+#include <net/page_pool/types.h>
 #include <net/sock.h>
 
+#include "devmem.h"
 #include "page_pool_priv.h"
 #include "netdev-genl-gen.h"
 
···
 page_pool_nl_fill(struct sk_buff *rsp, const struct page_pool *pool,
 		  const struct genl_info *info)
 {
+	struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
 	size_t inflight, refsz;
 	void *hdr;
 
···
 	if (pool->user.detach_time &&
 	    nla_put_uint(rsp, NETDEV_A_PAGE_POOL_DETACH_TIME,
 			 pool->user.detach_time))
+		goto err_cancel;
+
+	if (binding && nla_put_u32(rsp, NETDEV_A_PAGE_POOL_DMABUF, binding->id))
 		goto err_cancel;
 
 	genlmsg_end(rsp, hdr);
···
 	if (!hlist_unhashed(&pool->user.list))
 		hlist_del(&pool->user.list);
 	mutex_unlock(&page_pools_lock);
+}
+
+int page_pool_check_memory_provider(struct net_device *dev,
+				    struct netdev_rx_queue *rxq)
+{
+	struct net_devmem_dmabuf_binding *binding = rxq->mp_params.mp_priv;
+	struct page_pool *pool;
+	struct hlist_node *n;
+
+	if (!binding)
+		return 0;
+
+	mutex_lock(&page_pools_lock);
+	hlist_for_each_entry_safe(pool, n, &dev->page_pools, user.list) {
+		if (pool->mp_priv != binding)
+			continue;
+
+		if (pool->slow.queue_idx == get_netdev_rx_queue_index(rxq)) {
+			mutex_unlock(&page_pools_lock);
+			return 0;
+		}
+	}
+	mutex_unlock(&page_pools_lock);
+	return -ENODATA;
 }
 
 static void page_pool_unreg_netdev_wipe(struct net_device *netdev)

net/core/skbuff.c

···
 #include <linux/textsearch.h>
 
 #include "dev.h"
+#include "netmem_priv.h"
 #include "sock_destructor.h"
 
 #ifdef CONFIG_SKB_EXTENSIONS
···
 		skb_get(list);
 }
 
-static bool is_pp_page(struct page *page)
+static bool is_pp_netmem(netmem_ref netmem)
 {
-	return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
+	return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
 }
 
 int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
···
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 bool napi_pp_put_page(netmem_ref netmem)
 {
-	struct page *page = netmem_to_page(netmem);
-
-	page = compound_head(page);
+	netmem = netmem_compound_head(netmem);
 
 	/* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
 	 * in order to preserve any existing bits, such as bit 0 for the
···
 	 * and page_is_pfmemalloc() is checked in __page_pool_put_page()
 	 * to avoid recycling the pfmemalloc page.
 	 */
-	if (unlikely(!is_pp_page(page)))
+	if (unlikely(!is_pp_netmem(netmem)))
 		return false;
 
-	page_pool_put_full_netmem(page->pp, page_to_netmem(page), false);
+	page_pool_put_full_netmem(netmem_get_pp(netmem), netmem, false);
 
 	return true;
 }
···
 static int skb_pp_frag_ref(struct sk_buff *skb)
 {
 	struct skb_shared_info *shinfo;
-	struct page *head_page;
+	netmem_ref head_netmem;
 	int i;
 
 	if (!skb->pp_recycle)
···
 	shinfo = skb_shinfo(skb);
 
 	for (i = 0; i < shinfo->nr_frags; i++) {
-		head_page = compound_head(skb_frag_page(&shinfo->frags[i]));
-		if (likely(is_pp_page(head_page)))
-			page_pool_ref_page(head_page);
+		head_netmem = netmem_compound_head(shinfo->frags[i].netmem);
+		if (likely(is_pp_netmem(head_netmem)))
+			page_pool_ref_netmem(head_netmem);
 		else
-			page_ref_inc(head_page);
+			page_ref_inc(netmem_to_page(head_netmem));
 	}
 	return 0;
 }
···
 		u32 p_off, p_len, copied;
 		struct page *p;
 		u8 *vaddr;
+
+		if (skb_frag_is_net_iov(frag)) {
+			printk("%sskb frag %d: not readable\n", level, i);
+			len -= skb_frag_size(frag);
+			if (!len)
+				break;
+			continue;
+		}
 
 		skb_frag_foreach_page(frag, skb_frag_off(frag),
 				      skb_frag_size(frag), p, p_off, p_len,
···
 	if (skb_shared(skb) || skb_unclone(skb, gfp_mask))
 		return -EINVAL;
 
+	if (!skb_frags_readable(skb))
+		return -EFAULT;
+
 	if (!num_frags)
 		goto release;
 
···
 	struct sk_buff *n;
 	unsigned int size;
 	int headerlen;
+
+	if (!skb_frags_readable(skb))
+		return NULL;
 
 	if (WARN_ON_ONCE(skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST))
 		return NULL;
···
 	int head_copy_len, head_copy_off;
 	struct sk_buff *n;
 	int oldheadroom;
+
+	if (!skb_frags_readable(skb))
+		return NULL;
 
 	if (WARN_ON_ONCE(skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST))
 		return NULL;
···
 	 */
 	int i, k, eat = (skb->tail + delta) - skb->end;
 
+	if (!skb_frags_readable(skb))
+		return NULL;
+
 	if (eat > 0 || skb_cloned(skb)) {
 		if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
 				     GFP_ATOMIC))
···
 		offset += copy;
 		to     += copy;
 	}
+
+	if (!skb_frags_readable(skb))
+		goto fault;
 
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
···
 	/*
 	 * then map the fragments
 	 */
+	if (!skb_frags_readable(skb))
+		return false;
+
 	for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
 		const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
+
+		if (WARN_ON_ONCE(!skb_frag_page(f)))
+			return false;
 
 		if (__splice_segment(skb_frag_page(f),
 				     skb_frag_off(f), skb_frag_size(f),
···
 		from += copy;
 	}
 
+	if (!skb_frags_readable(skb))
+		goto fault;
+
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 		int end;
···
 		offset += copy;
 		pos	= copy;
 	}
+
+	if (WARN_ON_ONCE(!skb_frags_readable(skb)))
+		return 0;
 
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
···
 		to     += copy;
 		pos	= copy;
 	}
+
+	if (!skb_frags_readable(skb))
+		return 0;
 
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
···
 		skb_shinfo(skb1)->frags[i] = skb_shinfo(skb)->frags[i];
 
 	skb_shinfo(skb1)->nr_frags = skb_shinfo(skb)->nr_frags;
+	skb1->unreadable	   = skb->unreadable;
 	skb_shinfo(skb)->nr_frags  = 0;
 	skb1->data_len		   = skb->data_len;
 	skb1->len		   += skb1->data_len;
···
 		pos += size;
 	}
 	skb_shinfo(skb1)->nr_frags = k;
+
+	skb1->unreadable = skb->unreadable;
 }
 
 /**
···
 		*data = st->cur_skb->data + (abs_offset - st->stepped_offset);
 		return block_limit - abs_offset;
 	}
+
+	if (!skb_frags_readable(st->cur_skb))
+		return 0;
 
 	if (st->frag_idx == 0 && !st->frag_data)
 		st->stepped_offset += skb_headlen(st->cur_skb);
···
 	if (to->pp_recycle != from->pp_recycle)
 		return false;
 
-	if (len <= skb_tailroom(to)) {
+	if (skb_frags_readable(from) != skb_frags_readable(to))
+		return false;
+
+	if (len <= skb_tailroom(to) && skb_frags_readable(from)) {
 		if (len)
 			BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));
 		*delta_truesize = 0;
···
 {
 	if (!pskb_may_pull(skb, write_len))
 		return -ENOMEM;
+
+	if (!skb_frags_readable(skb))
+		return -EFAULT;
 
 	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
 		return 0;
···
 {
 	if (skb->data_len) {
 		if (skb->data_len > skb->end - skb->tail ||
-		    skb_cloned(skb))
+		    skb_cloned(skb) || !skb_frags_readable(skb))
 			return;
 
 		/* Nice, we can free page frag(s) right now */

net/core/sock.c

···
 #include <linux/netdevice.h>
 #include <net/protocol.h>
 #include <linux/skbuff.h>
+#include <linux/skbuff_ref.h>
 #include <net/net_namespace.h>
 #include <net/request_sock.h>
 #include <net/sock.h>
···
 	return 0;
 }
 
+#ifdef CONFIG_PAGE_POOL
+
+/* This is the number of tokens that the user can SO_DEVMEM_DONTNEED in
+ * 1 syscall. The limit exists to limit the amount of memory the kernel
+ * allocates to copy these tokens.
+ */
+#define MAX_DONTNEED_TOKENS 128
+
+static noinline_for_stack int
+sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen)
+{
+	unsigned int num_tokens, i, j, k, netmem_num = 0;
+	struct dmabuf_token *tokens;
+	netmem_ref netmems[16];
+	int ret = 0;
+
+	if (!sk_is_tcp(sk))
+		return -EBADF;
+
+	if (optlen % sizeof(struct dmabuf_token) ||
+	    optlen > sizeof(*tokens) * MAX_DONTNEED_TOKENS)
+		return -EINVAL;
+
+	tokens = kvmalloc_array(optlen, sizeof(*tokens), GFP_KERNEL);
+	if (!tokens)
+		return -ENOMEM;
+
+	num_tokens = optlen / sizeof(struct dmabuf_token);
+	if (copy_from_sockptr(tokens, optval, optlen)) {
+		kvfree(tokens);
+		return -EFAULT;
+	}
+
+	xa_lock_bh(&sk->sk_user_frags);
+	for (i = 0; i < num_tokens; i++) {
+		for (j = 0; j < tokens[i].token_count; j++) {
+			netmem_ref netmem = (__force netmem_ref)__xa_erase(
+				&sk->sk_user_frags, tokens[i].token_start + j);
+
+			if (netmem &&
+			    !WARN_ON_ONCE(!netmem_is_net_iov(netmem))) {
+				netmems[netmem_num++] = netmem;
+				if (netmem_num == ARRAY_SIZE(netmems)) {
+					xa_unlock_bh(&sk->sk_user_frags);
+					for (k = 0; k < netmem_num; k++)
+						WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
+					netmem_num = 0;
+					xa_lock_bh(&sk->sk_user_frags);
+				}
+				ret++;
+			}
+		}
+	}
+
+	xa_unlock_bh(&sk->sk_user_frags);
+	for (k = 0; k < netmem_num; k++)
+		WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
+
+	kvfree(tokens);
+	return ret;
+}
+#endif
+
 void sockopt_lock_sock(struct sock *sk)
 {
 	/* When current->bpf_ctx is set, the setsockopt is called from
···
 			ret = -EOPNOTSUPP;
 		return ret;
 		}
+#ifdef CONFIG_PAGE_POOL
+	case SO_DEVMEM_DONTNEED:
+		return sock_devmem_dontneed(sk, optval, optlen);
+#endif
 	}
 
 	sockopt_lock_sock(sk);

net/ethtool/common.c

···
 {
 	u64 max_rxnfc_in_use;
 	u32 max_rxfh_in_use;
+	int max_mp_in_use;
 
 	/* ensure the new Rx count fits within the configured Rx flow
 	 * indirection table/rxnfc settings
···
 	if (channels.combined_count + channels.rx_count <= max_rxnfc_in_use) {
 		if (info)
 			GENL_SET_ERR_MSG(info, "requested channel counts are too low for existing ntuple filter settings");
+		return -EINVAL;
+	}
+
+	max_mp_in_use = dev_get_min_mp_channel_count(dev);
+	if (channels.combined_count + channels.rx_count <= max_mp_in_use) {
+		if (info)
+			GENL_SET_ERR_MSG_FMT(info, "requested channel counts are too low for existing memory provider setting (%d)", max_mp_in_use);
 		return -EINVAL;
 	}
 

net/ipv4/esp4.c

···
 	 */
 	if (req->src != req->dst)
 		for (sg = sg_next(req->src); sg; sg = sg_next(sg))
-			skb_page_unref(sg_page(sg), skb->pp_recycle);
+			skb_page_unref(page_to_netmem(sg_page(sg)),
+				       skb->pp_recycle);
 }
 
 #ifdef CONFIG_INET_ESPINTCP

net/ipv4/tcp.c

···
 #include <trace/events/tcp.h>
 #include <net/rps.h>
 
+#include "../core/devmem.h"
+
 /* Track pending CMSGs. */
 enum {
 	TCP_CMSG_INQ = 1,
···
 
 	set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
 	sk_sockets_allocated_inc(sk);
+	xa_init_flags(&sk->sk_user_frags, XA_FLAGS_ALLOC1);
 }
 EXPORT_SYMBOL(tcp_init_sock);
 
···
 				skb = tcp_recv_skb(sk, seq, &offset);
 			}
 
+			if (!skb_frags_readable(skb))
+				break;
+
 			if (TCP_SKB_CB(skb)->has_rxtstamp) {
 				tcp_update_recv_tstamps(skb, tss);
 				zc->msg_flags |= TCP_CMSG_TS;
···
 			break;
 		}
 		page = skb_frag_page(frags);
+		if (WARN_ON_ONCE(!page))
+			break;
+
 		prefetchw(page);
 		pages[pages_to_map++] = page;
 		length += PAGE_SIZE;
···
 	return inq;
 }
 
+/* batch __xa_alloc() calls and reduce xa_lock()/xa_unlock() overhead. */
+struct tcp_xa_pool {
+	u8		max; /* max <= MAX_SKB_FRAGS */
+	u8		idx; /* idx <= max */
+	__u32		tokens[MAX_SKB_FRAGS];
+	netmem_ref	netmems[MAX_SKB_FRAGS];
+};
+
+static void tcp_xa_pool_commit_locked(struct sock *sk, struct tcp_xa_pool *p)
+{
+	int i;
+
+	/* Commit part that has been copied to user space. */
+	for (i = 0; i < p->idx; i++)
+		__xa_cmpxchg(&sk->sk_user_frags, p->tokens[i], XA_ZERO_ENTRY,
+			     (__force void *)p->netmems[i], GFP_KERNEL);
+	/* Rollback what has been pre-allocated and is no longer needed. */
+	for (; i < p->max; i++)
+		__xa_erase(&sk->sk_user_frags, p->tokens[i]);
+
+	p->max = 0;
+	p->idx = 0;
+}
+
+static void tcp_xa_pool_commit(struct sock *sk, struct tcp_xa_pool *p)
+{
+	if (!p->max)
+		return;
+
+	xa_lock_bh(&sk->sk_user_frags);
+
+	tcp_xa_pool_commit_locked(sk, p);
+
+	xa_unlock_bh(&sk->sk_user_frags);
+}
+
+static int tcp_xa_pool_refill(struct sock *sk, struct tcp_xa_pool *p,
+			      unsigned int max_frags)
+{
+	int err, k;
+
+	if (p->idx < p->max)
+		return 0;
+
+	xa_lock_bh(&sk->sk_user_frags);
+
+	tcp_xa_pool_commit_locked(sk, p);
+
+	for (k = 0; k < max_frags; k++) {
+		err = __xa_alloc(&sk->sk_user_frags, &p->tokens[k],
+				 XA_ZERO_ENTRY, xa_limit_31b, GFP_KERNEL);
+		if (err)
+			break;
+	}
+
+	xa_unlock_bh(&sk->sk_user_frags);
+
+	p->max = k;
+	p->idx = 0;
+	return k ? 0 : err;
+}
+
+/* On error, returns the -errno. On success, returns number of bytes sent to the
+ * user. May not consume all of @remaining_len.
+ */
+static int tcp_recvmsg_dmabuf(struct sock *sk, const struct sk_buff *skb,
+			      unsigned int offset, struct msghdr *msg,
+			      int remaining_len)
+{
+	struct dmabuf_cmsg dmabuf_cmsg = { 0 };
+	struct tcp_xa_pool tcp_xa_pool;
+	unsigned int start;
+	int i, copy, n;
+	int sent = 0;
+	int err = 0;
+
+	tcp_xa_pool.max = 0;
+	tcp_xa_pool.idx = 0;
+	do {
+		start = skb_headlen(skb);
+
+		if (skb_frags_readable(skb)) {
+			err = -ENODEV;
+			goto out;
+		}
+
+		/* Copy header. */
+		copy = start - offset;
+		if (copy > 0) {
+			copy = min(copy, remaining_len);
+
+			n = copy_to_iter(skb->data + offset, copy,
+					 &msg->msg_iter);
+			if (n != copy) {
+				err = -EFAULT;
+				goto out;
+			}
+
+			offset += copy;
+			remaining_len -= copy;
+
+			/* First a dmabuf_cmsg for # bytes copied to user
+			 * buffer.
+			 */
+			memset(&dmabuf_cmsg, 0, sizeof(dmabuf_cmsg));
+			dmabuf_cmsg.frag_size = copy;
+			err = put_cmsg(msg, SOL_SOCKET, SO_DEVMEM_LINEAR,
+				       sizeof(dmabuf_cmsg), &dmabuf_cmsg);
+			if (err || msg->msg_flags & MSG_CTRUNC) {
+				msg->msg_flags &= ~MSG_CTRUNC;
+				if (!err)
+					err = -ETOOSMALL;
+				goto out;
+			}
+
+			sent += copy;
+
+			if (remaining_len == 0)
+				goto out;
+		}
+
+		/* after that, send information of dmabuf pages through a
+		 * sequence of cmsg
+		 */
+		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+			struct net_iov *niov;
+			u64 frag_offset;
+			int end;
+
+			/* !skb_frags_readable() should indicate that ALL the
+			 * frags in this skb are dmabuf net_iovs. We're checking
+			 * for that flag above, but also check individual frags
+			 * here. If the tcp stack is not setting
+			 * skb_frags_readable() correctly, we still don't want
+			 * to crash here.
+			 */
+			if (!skb_frag_net_iov(frag)) {
+				net_err_ratelimited("Found non-dmabuf skb with net_iov");
+				err = -ENODEV;
+				goto out;
+			}
+
+			niov = skb_frag_net_iov(frag);
+			end = start + skb_frag_size(frag);
+			copy = end - offset;
+
+			if (copy > 0) {
+				copy = min(copy, remaining_len);
+
+				frag_offset = net_iov_virtual_addr(niov) +
+					      skb_frag_off(frag) + offset -
+					      start;
+				dmabuf_cmsg.frag_offset = frag_offset;
+				dmabuf_cmsg.frag_size = copy;
+				err = tcp_xa_pool_refill(sk, &tcp_xa_pool,
+							 skb_shinfo(skb)->nr_frags - i);
+				if (err)
+					goto out;
+
+				/* Will perform the exchange later */
+				dmabuf_cmsg.frag_token = tcp_xa_pool.tokens[tcp_xa_pool.idx];
+				dmabuf_cmsg.dmabuf_id = net_iov_binding_id(niov);
+
+				offset += copy;
+				remaining_len -= copy;
+
+				err = put_cmsg(msg, SOL_SOCKET,
+					       SO_DEVMEM_DMABUF,
+					       sizeof(dmabuf_cmsg),
+					       &dmabuf_cmsg);
+				if (err || msg->msg_flags & MSG_CTRUNC) {
+					msg->msg_flags &= ~MSG_CTRUNC;
+					if (!err)
+						err = -ETOOSMALL;
+					goto out;
+				}
+
+				atomic_long_inc(&niov->pp_ref_count);
+				tcp_xa_pool.netmems[tcp_xa_pool.idx++] = skb_frag_netmem(frag);
+
+				sent += copy;
+
+				if (remaining_len == 0)
+					goto out;
+			}
+			start = end;
+		}
+
+		tcp_xa_pool_commit(sk, &tcp_xa_pool);
+		if (!remaining_len)
+			goto out;
+
+		/* if remaining_len is not satisfied yet, we need to go to the
+		 * next frag in the frag_list to satisfy remaining_len.
+		 */
+		skb = skb_shinfo(skb)->frag_list ?: skb->next;
+
+		offset = offset - start;
+	} while (skb);
+
+	if (remaining_len) {
+		err = -EFAULT;
+		goto out;
+	}
+
+out:
+	tcp_xa_pool_commit(sk, &tcp_xa_pool);
+	if (!sent)
+		sent = err;
+
+	return sent;
+}
+
 /*
  *	This routine copies from a sock struct into the user buffer.
  *
···
 			      int *cmsg_flags)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+	int last_copied_dmabuf = -1; /* uninitialized */
 	int copied = 0;
 	u32 peek_seq;
 	u32 *seq;
···
 		}
 
 		if (!(flags & MSG_TRUNC)) {
-			err = skb_copy_datagram_msg(skb, offset, msg, used);
-			if (err) {
-				/* Exception. Bailout! */
-				if (!copied)
-					copied = -EFAULT;
+			if (last_copied_dmabuf != -1 &&
+			    last_copied_dmabuf != !skb_frags_readable(skb))
 				break;
+
+			if (skb_frags_readable(skb)) {
+				err = skb_copy_datagram_msg(skb, offset, msg,
+							    used);
+				if (err) {
+					/* Exception. Bailout! */
+					if (!copied)
+						copied = -EFAULT;
+					break;
+				}
+			} else {
+				if (!(flags & MSG_SOCK_DEVMEM)) {
+					/* dmabuf skbs can only be received
+					 * with the MSG_SOCK_DEVMEM flag.
+					 */
+					if (!copied)
+						copied = -EFAULT;
+
+					break;
+				}
+
+				err = tcp_recvmsg_dmabuf(sk, skb, offset, msg,
+							 used);
+				if (err <= 0) {
+					if (!copied)
+						copied = -EFAULT;
+
+					break;
+				}
+				used = err;
 			}
 		}
+
+		last_copied_dmabuf = !skb_frags_readable(skb);
 
 		WRITE_ONCE(*seq, *seq + used);
 		copied += used;

net/ipv4/tcp_input.c

···
 	for (end_of_skbs = true; skb != NULL && skb != tail; skb = n) {
 		n = tcp_skb_next(skb, list);
 
+		if (!skb_frags_readable(skb))
+			goto skip_this;
+
 		/* No new bits? It is possible on ofo queue. */
 		if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
 			skb = tcp_collapse_one(sk, skb, list, root);
···
 			break;
 		}
 
-		if (n && n != tail && tcp_skb_can_collapse_rx(skb, n) &&
+		if (n && n != tail && skb_frags_readable(n) &&
+		    tcp_skb_can_collapse_rx(skb, n) &&
 		    TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(n)->seq) {
 			end_of_skbs = false;
 			break;
 		}
 
+skip_this:
 		/* Decided to skip this, advance start seq. */
 		start = TCP_SKB_CB(skb)->end_seq;
 	}
 	if (end_of_skbs ||
-	    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
+	    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) ||
+	    !skb_frags_readable(skb))
 		return;
 
 	__skb_queue_head_init(&tmp);
···
 				if (!skb ||
 				    skb == tail ||
 				    !tcp_skb_can_collapse_rx(nskb, skb) ||
-				    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
+				    (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) ||
+				    !skb_frags_readable(skb))
 					goto end;
 			}
 		}

net/ipv4/tcp_ipv4.c

···
 #include <linux/seq_file.h>
 #include <linux/inetdevice.h>
 #include <linux/btf_ids.h>
+#include <linux/skbuff_ref.h>
 
 #include <crypto/hash.h>
 #include <linux/scatterlist.h>
···
 }
 #endif
 
+static void tcp_release_user_frags(struct sock *sk)
+{
+#ifdef CONFIG_PAGE_POOL
+	unsigned long index;
+	void *netmem;
+
+	xa_for_each(&sk->sk_user_frags, index, netmem)
+		WARN_ON_ONCE(!napi_pp_put_page((__force netmem_ref)netmem));
+#endif
+}
+
 void tcp_v4_destroy_sock(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+
+	tcp_release_user_frags(sk);
+
+	xa_destroy(&sk->sk_user_frags);
 
 	trace_tcp_destroy_sock(sk);
 

net/ipv4/tcp_minisocks.c

···
 
 	__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);
 
+	xa_init_flags(&newsk->sk_user_frags, XA_FLAGS_ALLOC1);
+
 	return newsk;
 }
 EXPORT_SYMBOL(tcp_create_openreq_child);

net/ipv4/tcp_output.c

···
 
 		if (unlikely(TCP_SKB_CB(skb)->eor) ||
 		    tcp_has_tx_tstamp(skb) ||
-		    !skb_pure_zcopy_same(skb, next))
+		    !skb_pure_zcopy_same(skb, next) ||
+		    skb_frags_readable(skb) != skb_frags_readable(next))
 			return false;
 
 		len -= skb->len;
···
 	if (tcp_skb_pcount(skb) > 1)
 		return false;
 	if (skb_cloned(skb))
+		return false;
+	if (!skb_frags_readable(skb))
 		return false;
 	/* Some heuristics for collapsing over SACK'd could be invented */
 	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)

net/ipv6/esp6.c

···
 	 */
 	if (req->src != req->dst)
 		for (sg = sg_next(req->src); sg; sg = sg_next(sg))
-			skb_page_unref(sg_page(sg), skb->pp_recycle);
+			skb_page_unref(page_to_netmem(sg_page(sg)),
+				       skb->pp_recycle);
 }
 
 #ifdef CONFIG_INET6_ESPINTCP

net/packet/af_packet.c

···
 		}
 	}
 
-	snaplen = skb->len;
+	snaplen = skb_frags_readable(skb) ? skb->len : skb_headlen(skb);
 
 	res = run_filter(skb, sk, snaplen);
 	if (!res)
···
 		}
 	}
 
-	snaplen = skb->len;
+	snaplen = skb_frags_readable(skb) ? skb->len : skb_headlen(skb);
 
 	res = run_filter(skb, sk, snaplen);
 	if (!res)

net/xdp/xsk_buff_pool.c

···
 		goto err_unreg_pool;
 	}
 
+	if (dev_get_min_mp_channel_count(netdev)) {
+		err = -EBUSY;
+		goto err_unreg_pool;
+	}
+
 	bpf.command = XDP_SETUP_XSK_POOL;
 	bpf.xsk.pool = pool;
 	bpf.xsk.queue_id = queue_id;

tools/include/uapi/linux/netdev.h

···
 	NETDEV_A_PAGE_POOL_INFLIGHT,
 	NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
 	NETDEV_A_PAGE_POOL_DETACH_TIME,
+	NETDEV_A_PAGE_POOL_DMABUF,
 
 	__NETDEV_A_PAGE_POOL_MAX,
 	NETDEV_A_PAGE_POOL_MAX = (__NETDEV_A_PAGE_POOL_MAX - 1)
···
 	NETDEV_A_QUEUE_IFINDEX,
 	NETDEV_A_QUEUE_TYPE,
 	NETDEV_A_QUEUE_NAPI_ID,
+	NETDEV_A_QUEUE_DMABUF,
 
 	__NETDEV_A_QUEUE_MAX,
 	NETDEV_A_QUEUE_MAX = (__NETDEV_A_QUEUE_MAX - 1)
···
 };
 
 enum {
+	NETDEV_A_DMABUF_IFINDEX = 1,
+	NETDEV_A_DMABUF_QUEUES,
+	NETDEV_A_DMABUF_FD,
+	NETDEV_A_DMABUF_ID,
+
+	__NETDEV_A_DMABUF_MAX,
+	NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
+};
+
+enum {
 	NETDEV_CMD_DEV_GET = 1,
 	NETDEV_CMD_DEV_ADD_NTF,
 	NETDEV_CMD_DEV_DEL_NTF,
···
 	NETDEV_CMD_QUEUE_GET,
 	NETDEV_CMD_NAPI_GET,
 	NETDEV_CMD_QSTATS_GET,
+	NETDEV_CMD_BIND_RX,
 
 	__NETDEV_CMD_MAX,
 	NETDEV_CMD_MAX = (__NETDEV_CMD_MAX - 1)

tools/net/ynl/lib/.gitignore

···
 __pycache__/
+*.d

tools/testing/selftests/net/.gitignore

···
 ipv6_flowlabel_mgr
 log.txt
 msg_zerocopy
+ncdevmem
 nettest
 psock_fanout
 psock_snd

tools/testing/selftests/net/Makefile

···
 TEST_PROGS += vlan_hw_filter.sh
 TEST_PROGS += bpf_offload.py
 
+# YNL files, must be before "include ..lib.mk"
+EXTRA_CLEAN += $(OUTPUT)/libynl.a
+YNL_GEN_FILES := ncdevmem
+TEST_GEN_FILES += $(YNL_GEN_FILES)
+
 TEST_FILES := settings
 TEST_FILES += in_netns.sh lib.sh net_helper.sh setup_loopback.sh setup_veth.sh
 
···
 TEST_INCLUDES := forwarding/lib.sh
 
 include ../lib.mk
+
+# YNL build
+YNL_GENS := netdev
+include ynl.mk
 
 $(OUTPUT)/epoll_busy_poll: LDLIBS += -lcap
 $(OUTPUT)/reuseport_bpf_numa: LDLIBS += -lnuma

tools/testing/selftests/net/ncdevmem.c

···
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#define __EXPORTED_HEADERS__
+
+#include <linux/uio.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <string.h>
+#include <errno.h>
+#define __iovec_defined
+#include <fcntl.h>
+#include <malloc.h>
+#include <error.h>
+
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <sys/syscall.h>
+
+#include <linux/memfd.h>
+#include <linux/dma-buf.h>
+#include <linux/udmabuf.h>
+#include <libmnl/libmnl.h>
+#include <linux/types.h>
+#include <linux/netlink.h>
+#include <linux/genetlink.h>
+#include <linux/netdev.h>
+#include <time.h>
+#include <net/if.h>
+
+#include "netdev-user.h"
+#include <ynl.h>
+
+#define PAGE_SHIFT 12
+#define TEST_PREFIX "ncdevmem"
+#define NUM_PAGES 16000
+
+#ifndef MSG_SOCK_DEVMEM
+#define MSG_SOCK_DEVMEM 0x2000000
+#endif
+
+/*
+ * tcpdevmem netcat. Works similarly to netcat but does device memory TCP
+ * instead of regular TCP. Uses udmabuf to mock a dmabuf provider.
+ *
+ * Usage:
+ *
+ *	On server:
+ *	ncdevmem -s <server IP> -c <client IP> -f eth1 -l -p 5201 -v 7
+ *
+ *	On client:
+ *	yes $(echo -e \\x01\\x02\\x03\\x04\\x05\\x06) | \
+ *		tr \\n \\0 | \
+ *		head -c 5G | \
+ *		nc <server IP> 5201 -p 5201
+ *
+ * Note this is compatible with regular netcat. i.e. the sender or receiver can
+ * be replaced with regular netcat to test the RX or TX path in isolation.
+ */
+
+static char *server_ip = "192.168.1.4";
+static char *client_ip = "192.168.1.2";
+static char *port = "5201";
+static size_t do_validation;
+static int start_queue = 8;
+static int num_queues = 8;
+static char *ifname = "eth1";
+static unsigned int ifindex;
+static unsigned int dmabuf_id;
+
+void print_bytes(void *ptr, size_t size)
+{
+	unsigned char *p = ptr;
+	int i;
+
+	for (i = 0; i < size; i++)
+		printf("%02hhX ", p[i]);
+	printf("\n");
+}
+
+void print_nonzero_bytes(void *ptr, size_t size)
+{
+	unsigned char *p = ptr;
+	unsigned int i;
+
+	for (i = 0; i < size; i++)
+		putchar(p[i]);
+	printf("\n");
+}
+
+void validate_buffer(void *line, size_t size)
+{
+	static unsigned char seed = 1;
+	unsigned char *ptr = line;
+	int errors = 0;
+	size_t i;
+
+	for (i = 0; i < size; i++) {
+		if (ptr[i] != seed) {
+			fprintf(stderr,
+				"Failed validation: expected=%u, actual=%u, index=%lu\n",
+				seed, ptr[i], i);
+			errors++;
+			if (errors > 20)
+				error(1, 0, "validation failed.");
+		}
+		seed++;
+		if (seed == do_validation)
+			seed = 0;
+	}
+
+	fprintf(stdout, "Validated buffer\n");
+}
+
+#define run_command(cmd, ...)                                           \
+	({                                                              \
+		char command[256];                                      \
+		memset(command, 0, sizeof(command));                    \
+		snprintf(command, sizeof(command), cmd, ##__VA_ARGS__); \
+		printf("Running: %s\n", command);                       \
+		system(command);                                        \
+	})
+
+static int reset_flow_steering(void)
+{
+	int ret = 0;
+
+	ret = run_command("sudo ethtool -K %s ntuple off", ifname);
+	if (ret)
+		return ret;
+
+	return run_command("sudo ethtool -K %s ntuple on", ifname);
+}
+
+static int configure_headersplit(bool on)
+{
+	return run_command("sudo ethtool -G %s tcp-data-split %s", ifname,
+			   on ? "on" : "off");
+}
+
+static int configure_rss(void)
+{
+	return run_command("sudo ethtool -X %s equal %d", ifname, start_queue);
+}
+
+static int configure_channels(unsigned int rx, unsigned int tx)
+{
+	return run_command("sudo ethtool -L %s rx %u tx %u", ifname, rx, tx);
+}
+
+static int configure_flow_steering(void)
+{
+	return run_command("sudo ethtool -N %s flow-type tcp4 src-ip %s dst-ip %s src-port %s dst-port %s queue %d",
+			   ifname, client_ip, server_ip, port, port, start_queue);
+}
+
+static int bind_rx_queue(unsigned int ifindex, unsigned int dmabuf_fd,
+			 struct netdev_queue_id *queues,
+			 unsigned int n_queue_index, struct ynl_sock **ys)
+{
+	struct netdev_bind_rx_req *req = NULL;
+	struct netdev_bind_rx_rsp *rsp = NULL;
+	struct ynl_error yerr;
+
+	*ys = ynl_sock_create(&ynl_netdev_family, &yerr);
+	if (!*ys) {
+		fprintf(stderr, "YNL: %s\n", yerr.msg);
+		return -1;
+	}
+
+	req = netdev_bind_rx_req_alloc();
+	netdev_bind_rx_req_set_ifindex(req, ifindex);
+	netdev_bind_rx_req_set_fd(req, dmabuf_fd);
+	__netdev_bind_rx_req_set_queues(req, queues, n_queue_index);
+
+	rsp = netdev_bind_rx(*ys, req);
+	if (!rsp) {
+		perror("netdev_bind_rx");
+		goto err_close;
+	}
+
+	if (!rsp->_present.id) {
+		perror("id not present");
+		goto err_close;
+	}
+
+	printf("got dmabuf id=%d\n", rsp->id);
+	dmabuf_id = rsp->id;
+
+	netdev_bind_rx_req_free(req);
+	netdev_bind_rx_rsp_free(rsp);
+
+	return 0;
+
+err_close:
+	fprintf(stderr, "YNL failed: %s\n", (*ys)->err.msg);
+	netdev_bind_rx_req_free(req);
+	ynl_sock_destroy(*ys);
+	return -1;
+}
+
+static void create_udmabuf(int *devfd, int *memfd, int *buf, size_t dmabuf_size)
+{
+	struct udmabuf_create create;
+	int ret;
+
+	*devfd = open("/dev/udmabuf", O_RDWR);
+	if (*devfd < 0) {
+		error(70, 0,
+		      "%s: [skip,no-udmabuf: Unable to access DMA buffer device file]\n",
+		      TEST_PREFIX);
+	}
+
+	*memfd = memfd_create("udmabuf-test", MFD_ALLOW_SEALING);
+	if (*memfd < 0)
+		error(70, 0, "%s: [skip,no-memfd]\n", TEST_PREFIX);
+
+	/* Required for udmabuf */
+	ret = fcntl(*memfd, F_ADD_SEALS, F_SEAL_SHRINK);
+	if (ret < 0)
+		error(73, 0, "%s: [skip,fcntl-add-seals]\n", TEST_PREFIX);
+
+	ret = ftruncate(*memfd, dmabuf_size);
+	if (ret == -1)
+		error(74, 0, "%s: [FAIL,memfd-truncate]\n", TEST_PREFIX);
+
+	memset(&create, 0, sizeof(create));
+
+	create.memfd = *memfd;
+	create.offset = 0;
+	create.size = dmabuf_size;
+	*buf = ioctl(*devfd, UDMABUF_CREATE, &create);
+	if (*buf < 0)
+		error(75, 0, "%s: [FAIL, create udmabuf]\n", TEST_PREFIX);
+}
+
+int do_server(void)
+{
+	char ctrl_data[sizeof(int) * 20000];
+	struct netdev_queue_id *queues;
+	size_t non_page_aligned_frags = 0;
+	struct sockaddr_in client_addr;
+	struct sockaddr_in server_sin;
+	size_t page_aligned_frags = 0;
+	int devfd, memfd, buf, ret;
+	size_t total_received = 0;
+	socklen_t client_addr_len;
+	bool is_devmem = false;
+	char *buf_mem = NULL;
+	struct ynl_sock *ys;
+	size_t dmabuf_size;
+	char iobuf[819200];
+	char buffer[256];
+	int socket_fd;
+	int client_fd;
+	size_t i = 0;
+	int opt = 1;
+
+	dmabuf_size = getpagesize() * NUM_PAGES;
+
+	create_udmabuf(&devfd, &memfd, &buf, dmabuf_size);
+
+	if (reset_flow_steering())
+		error(1, 0, "Failed to reset flow steering\n");
+
+	/* Configure RSS to divert all traffic from our devmem queues */
+	if (configure_rss())
+		error(1, 0, "Failed to configure rss\n");
+
+	/* Flow steer our devmem flows to start_queue */
+	if (configure_flow_steering())
+		error(1, 0, "Failed to configure flow steering\n");
+
+	sleep(1);
+
+	queues = malloc(sizeof(*queues) * num_queues);
+
+	for (i = 0; i < num_queues; i++) {
+		queues[i]._present.type = 1;
+		queues[i]._present.id = 1;
+		queues[i].type = NETDEV_QUEUE_TYPE_RX;
+		queues[i].id = start_queue + i;
+	}
+
+	if (bind_rx_queue(ifindex, buf, queues, num_queues, &ys))
+		error(1, 0, "Failed to bind\n");
+
+	buf_mem = mmap(NULL, dmabuf_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+		       buf, 0);
+	if (buf_mem == MAP_FAILED)
+		error(1, 0, "mmap()");
+
+	server_sin.sin_family = AF_INET;
+	server_sin.sin_port = htons(atoi(port));
+
+	ret = inet_pton(server_sin.sin_family, server_ip, &server_sin.sin_addr);
+	if (socket < 0)
+		error(79, 0, "%s: [FAIL, create socket]\n", TEST_PREFIX);
+
+	socket_fd = socket(server_sin.sin_family, SOCK_STREAM, 0);
+	if (socket < 0)
+		error(errno, errno, "%s: [FAIL, create socket]\n", TEST_PREFIX);
+
+	ret = setsockopt(socket_fd, SOL_SOCKET, SO_REUSEPORT, &opt,
+			 sizeof(opt));
+	if (ret)
+		error(errno, errno, "%s: [FAIL, set sock opt]\n", TEST_PREFIX);
+
+	ret = setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &opt,
+			 sizeof(opt));
+	if (ret)
+		error(errno, errno, "%s: [FAIL, set sock opt]\n", TEST_PREFIX);
+
+	printf("binding to address %s:%d\n", server_ip,
+	       ntohs(server_sin.sin_port));
+
+	ret = bind(socket_fd, &server_sin, sizeof(server_sin));
+	if (ret)
+		error(errno, errno, "%s: [FAIL, bind]\n", TEST_PREFIX);
+
+	ret = listen(socket_fd, 1);
+	if (ret)
+		error(errno, errno, "%s: [FAIL, listen]\n", TEST_PREFIX);
+
+	client_addr_len = sizeof(client_addr);
+
+	inet_ntop(server_sin.sin_family, &server_sin.sin_addr, buffer,
+		  sizeof(buffer));
+	printf("Waiting or connection on %s:%d\n", buffer,
+	       ntohs(server_sin.sin_port));
+	client_fd = accept(socket_fd, &client_addr, &client_addr_len);
+
+	inet_ntop(client_addr.sin_family, &client_addr.sin_addr, buffer,
+		  sizeof(buffer));
+	printf("Got connection from %s:%d\n", buffer,
+	       ntohs(client_addr.sin_port));
+
+	while (1) {
+		struct iovec iov = { .iov_base = iobuf,
+				     .iov_len = sizeof(iobuf) };
+		struct dmabuf_cmsg *dmabuf_cmsg = NULL;
+		struct dma_buf_sync sync = { 0 };
+		struct cmsghdr *cm = NULL;
+		struct msghdr msg = { 0 };
+		struct dmabuf_token token;
+		ssize_t ret;
+
+		is_devmem = false;
+		printf("\n\n");
+
+		msg.msg_iov = &iov;
+		msg.msg_iovlen = 1;
+		msg.msg_control = ctrl_data;
+		msg.msg_controllen = sizeof(ctrl_data);
+		ret = recvmsg(client_fd, &msg, MSG_SOCK_DEVMEM);
+		printf("recvmsg ret=%ld\n", ret);
+		if (ret < 0 && (errno == EAGAIN || errno == EWOULDBLOCK))
+			continue;
+		if (ret < 0) {
+			perror("recvmsg");
+			continue;
+		}
+		if (ret == 0) {
+			printf("client exited\n");
+			goto cleanup;
+		}
+
+		i++;
+		for (cm = CMSG_FIRSTHDR(&msg); cm; cm = CMSG_NXTHDR(&msg, cm)) {
+			if (cm->cmsg_level != SOL_SOCKET ||
+			    (cm->cmsg_type != SCM_DEVMEM_DMABUF &&
+			     cm->cmsg_type != SCM_DEVMEM_LINEAR)) {
+				fprintf(stdout, "skipping non-devmem cmsg\n");
+				continue;
+			}
+
+			dmabuf_cmsg = (struct dmabuf_cmsg *)CMSG_DATA(cm);
+			is_devmem = true;
+
+			if (cm->cmsg_type == SCM_DEVMEM_LINEAR) {
+				/* TODO: process data copied from skb's linear
+				 * buffer.
+				 */
+				fprintf(stdout,
+					"SCM_DEVMEM_LINEAR. dmabuf_cmsg->frag_size=%u\n",
+					dmabuf_cmsg->frag_size);
+
+				continue;
+			}
+
+			token.token_start = dmabuf_cmsg->frag_token;
+			token.token_count = 1;
+
+			total_received += dmabuf_cmsg->frag_size;
+			printf("received frag_page=%llu, in_page_offset=%llu, frag_offset=%llu, frag_size=%u, token=%u, total_received=%lu, dmabuf_id=%u\n",
+			       dmabuf_cmsg->frag_offset >> PAGE_SHIFT,
+			       dmabuf_cmsg->frag_offset % getpagesize(),
+			       dmabuf_cmsg->frag_offset, dmabuf_cmsg->frag_size,
+			       dmabuf_cmsg->frag_token, total_received,
+			       dmabuf_cmsg->dmabuf_id);
+
+			if (dmabuf_cmsg->dmabuf_id != dmabuf_id)
+				error(1, 0,
+				      "received on wrong dmabuf_id: flow steering error\n");
+
+			if (dmabuf_cmsg->frag_size % getpagesize())
+				non_page_aligned_frags++;
+			else
+				page_aligned_frags++;
+
+			sync.flags = DMA_BUF_SYNC_READ | DMA_BUF_SYNC_START;
+			ioctl(buf, DMA_BUF_IOCTL_SYNC, &sync);
+
+			if (do_validation)
+				validate_buffer(
+					((unsigned char *)buf_mem) +
+						dmabuf_cmsg->frag_offset,
+					dmabuf_cmsg->frag_size);
+			else
+				print_nonzero_bytes(
+					((unsigned char *)buf_mem) +
+						dmabuf_cmsg->frag_offset,
+					dmabuf_cmsg->frag_size);
+
+			sync.flags = DMA_BUF_SYNC_READ | DMA_BUF_SYNC_END;
+			ioctl(buf, DMA_BUF_IOCTL_SYNC, &sync);
+
+			ret = setsockopt(client_fd, SOL_SOCKET,
+					 SO_DEVMEM_DONTNEED, &token,
+					 sizeof(token));
+			if (ret != 1)
+				error(1, 0,
+				      "SO_DEVMEM_DONTNEED not enough tokens");
+		}
+		if (!is_devmem)
+			error(1, 0, "flow steering error\n");
+
+		printf("total_received=%lu\n", total_received);
+	}
+
+	fprintf(stdout, "%s: ok\n", TEST_PREFIX);
+
+	fprintf(stdout, "page_aligned_frags=%lu, non_page_aligned_frags=%lu\n",
+		page_aligned_frags, non_page_aligned_frags);
+
+	fprintf(stdout, "page_aligned_frags=%lu, non_page_aligned_frags=%lu\n",
+		page_aligned_frags, non_page_aligned_frags);
+
+cleanup:
+
+	munmap(buf_mem, dmabuf_size);
+	close(client_fd);
+	close(socket_fd);
+	close(buf);
+	close(memfd);
+	close(devfd);
+	ynl_sock_destroy(ys);
+
+	return 0;
+}
+
+void run_devmem_tests(void)
+{
+	struct netdev_queue_id *queues;
+	int devfd, memfd, buf;
+	struct ynl_sock *ys;
+	size_t dmabuf_size;
+	size_t i = 0;
+
+	dmabuf_size = getpagesize() * NUM_PAGES;
+
+	create_udmabuf(&devfd, &memfd, &buf, dmabuf_size);
+
+	/* Configure RSS to divert all traffic from our devmem queues */
+	if (configure_rss())
+		error(1, 0, "rss error\n");
+
+	queues = calloc(num_queues, sizeof(*queues));
+
+	if (configure_headersplit(1))
+		error(1, 0, "Failed to configure header split\n");
+
+	if (!bind_rx_queue(ifindex, buf, queues, num_queues, &ys))
+		error(1, 0, "Binding empty queues array should have failed\n");
+
+	for (i = 0; i < num_queues; i++) {
+		queues[i]._present.type = 1;
+		queues[i]._present.id = 1;
+		queues[i].type = NETDEV_QUEUE_TYPE_RX;
+		queues[i].id = start_queue + i;
+	}
+
+	if (configure_headersplit(0))
+		error(1, 0, "Failed to configure header split\n");
+
+	if (!bind_rx_queue(ifindex, buf, queues, num_queues, &ys))
+		error(1, 0, "Configure dmabuf with header split off should have failed\n");
+
+	if (configure_headersplit(1))
+		error(1, 0, "Failed to configure header split\n");
+
+	for (i = 0; i < num_queues; i++) {
+		queues[i]._present.type = 1;
+		queues[i]._present.id = 1;
+		queues[i].type = NETDEV_QUEUE_TYPE_RX;
+		queues[i].id = start_queue + i;
+	}
+
+	if (bind_rx_queue(ifindex, buf, queues, num_queues, &ys))
+		error(1, 0, "Failed to bind\n");
+
+	/* Deactivating a bound queue should not be legal */
+	if (!configure_channels(num_queues, num_queues - 1))
+		error(1, 0, "Deactivating a bound queue should be illegal.\n");
+
+	/* Closing the netlink socket does an implicit unbind */
+	ynl_sock_destroy(ys);
+}
+
+int main(int argc, char *argv[])
+{
+	int is_server = 0, opt;
+
+	while ((opt = getopt(argc, argv, "ls:c:p:v:q:t:f:")) != -1) {
+		switch (opt) {
+		case 'l':
+			is_server = 1;
+			break;
+		case 's':
+			server_ip = optarg;
+			break;
+		case 'c':
+			client_ip = optarg;
+			break;
+		case 'p':
+			port = optarg;
+			break;
+		case 'v':
+			do_validation = atoll(optarg);
+			break;
+		case 'q':
+			num_queues = atoi(optarg);
+			break;
+		case 't':
+			start_queue = atoi(optarg);
+			break;
+		case 'f':
+			ifname = optarg;
+			break;
+		case '?':
+			printf("unknown option: %c\n", optopt);
+			break;
+		}
+	}
+
+	ifindex = if_nametoindex(ifname);
+
+	for (; optind < argc; optind++)
+		printf("extra arguments: %s\n", argv[optind]);
+
+	run_devmem_tests();
+
+	if (is_server)
+		return do_server();
+
+	return 0;
+}