[PATCH net-next v7 4/9] net: devmem: Implement TX path

Mina Almasry
2025-03-08T21:40:54Z

Augment dmabuf binding to be able to handle TX. Additional to all the RX
binding, we also create tx_vec needed for the TX path.

Provide API for sendmsg to be able to send dmabufs bound to this device:

- Provide a new dmabuf_tx_cmsg which includes the dmabuf to send from.
- MSG_ZEROCOPY with SCM_DEVMEM_DMABUF cmsg indicates send from dma-buf.

Devmem is uncopyable, so piggyback off the existing MSG_ZEROCOPY
implementation, while disabling instances where MSG_ZEROCOPY falls back
to copying.

We additionally pipe the binding down to the new
zerocopy_fill_skb_from_devmem which fills a TX skb with net_iov netmems
instead of the traditional page netmems.

We also special case skb_frag_dma_map to return the dma-address of these
dmabuf net_iovs instead of attempting to map pages.

The TX path may release the dmabuf in a context where we cannot wait.
This happens when the user unbinds a TX dmabuf while there are still
references to its netmems in the TX path. In that case, the netmems will
be put_netmem'd from a context where we can't unmap the dmabuf, Resolve
this by making __net_devmem_dmabuf_binding_free schedule_work'd.

Based on work by Stanislav Fomichev <sdf@fomichev.me>. A lot of the meat
of the implementation came from devmem TCP RFC v1[1], which included the
TX path, but Stan did all the rebasing on top of netmem/net_iov.

Cc: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>

---

v6:
- Retain behavior that MSG_FASTOPEN succeeds even if cmsg is invalid
(Paolo).
- Rework the freeing of tx_vec slightly to improve readability. Now it
has its own err label (Paolo).
- Squash making unbinding scheduled work (Paolo).
- Add comment to clarify that net_iovs stuck in the transmit path hold
a ref on the underlying dmabuf binding (David).
- Fix the comment on how binding refcounting works on RX (the comment
was not matching the existing code behavior).

v5:
- Return -EFAULT from zerocopy_fill_skb_from_devmem (Stan)
- don't null check before kvfree (stan).

v4:
- Remove dmabuf_tx_cmsg definition and just use __u32 for the dma-buf id
(Willem).
- Check that iov_iter_type() is ITER_IOVEC in
zerocopy_fill_skb_from_iter() (Pavel).
- Fix binding->tx_vec not being freed on error paths (Paolo).
- Make devmem patch mutually exclusive with msg->ubuf_info path (Pavel).
- Check that MSG_ZEROCOPY and SOCK_ZEROCOPY are provided when
sockc.dmabuf_id is provided.
- Don't mm_account_pinned_pages() on devmem TX (Pavel).

v3:
- Use kvmalloc_array instead of kcalloc (Stan).
- Fix unreachable code warning (Simon).

v2:
- Remove dmabuf_offset from the dmabuf cmsg.
- Update zerocopy_fill_skb_from_devmem to interpret the
iov_base/iter_iov_addr as the offset into the dmabuf to send from
(Stan).
- Remove the confusing binding->tx_iter which is not needed if we
interpret the iov_base/iter_iov_addr as offset into the dmabuf (Stan).
- Remove check for binding->sgt and binding->sgt->nents in dmabuf
binding.
- Simplify the calculation of binding->tx_vec.
- Check in net_devmem_get_binding that the binding we're returning
has ifindex matching the sending socket (Willem).
---
include/linux/skbuff.h | 17 +++-
include/net/sock.h | 1 +
net/core/datagram.c | 48 ++++++++++-
net/core/devmem.c | 105 ++++++++++++++++++++++--
net/core/devmem.h | 61 +++++++++++---
net/core/netdev-genl.c | 64 ++++++++++++++-
net/core/skbuff.c | 18 ++--
net/core/sock.c | 6 ++
net/ipv4/ip_output.c | 3 +-
net/ipv4/tcp.c | 50 ++++++++---
net/ipv6/ip6_output.c | 3 +-
net/vmw_vsock/virtio_transport_common.c | 5 +-
12 files changed, 330 insertions(+), 51 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 14517e95a46c..67a7e069a9bf 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1707,13 +1707,16 @@ static inline void skb_set_end_offset(struct sk_buff *skb, unsigned int offset)
extern const struct ubuf_info_ops msg_zerocopy_ubuf_ops;

struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
- struct ubuf_info *uarg);
+ struct ubuf_info *uarg, bool devmem);

void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref);

+struct net_devmem_dmabuf_binding;
+
int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb, struct iov_iter *from,
- size_t length);
+ size_t length,
+ struct net_devmem_dmabuf_binding *binding);

int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
struct iov_iter *from, size_t length);
@@ -1721,12 +1724,14 @@ int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
static inline int skb_zerocopy_iter_dgram(struct sk_buff *skb,
struct msghdr *msg, int len)
{
- return __zerocopy_sg_from_iter(msg, skb->sk, skb, &msg->msg_iter, len);
+ return __zerocopy_sg_from_iter(msg, skb->sk, skb, &msg->msg_iter, len,
+ NULL);
}

int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
struct msghdr *msg, int len,
- struct ubuf_info *uarg);
+ struct ubuf_info *uarg,
+ struct net_devmem_dmabuf_binding *binding);

/* Internal */
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
@@ -3697,6 +3702,10 @@ static inline dma_addr_t __skb_frag_dma_map(struct device *dev,
size_t offset, size_t size,
enum dma_data_direction dir)
{
+ if (skb_frag_is_net_iov(frag)) {
+ return netmem_to_net_iov(frag->netmem)->dma_addr + offset +
+ frag->offset;
+ }
return dma_map_page(dev, skb_frag_page(frag),
skb_frag_off(frag) + offset, size, dir);
}
diff --git a/include/net/sock.h b/include/net/sock.h
index 8daf1b3b12c6..59875bed75e7 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1816,6 +1816,7 @@ struct sockcm_cookie {
u32 tsflags;
u32 ts_opt_id;
u32 priority;
+ u32 dmabuf_id;
};

static inline void sockcm_init(struct sockcm_cookie *sockc,
diff --git a/net/core/datagram.c b/net/core/datagram.c
index f0693707aece..09c74a1d836b 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -63,6 +63,8 @@
#include <net/busy_poll.h>
#include <crypto/hash.h>

+#include "devmem.h"
+
/*
* Is a socket 'connection oriented' ?
*/
@@ -692,9 +694,49 @@ int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
return 0;
}

+static int
+zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from,
+ int length,
+ struct net_devmem_dmabuf_binding *binding)
+{
+ int i = skb_shinfo(skb)->nr_frags;
+ size_t virt_addr, size, off;
+ struct net_iov *niov;
+
+ /* Devmem filling works by taking an IOVEC from the user where the
+ * iov_addrs are interpreted as an offset in bytes into the dma-buf to
+ * send from. We do not support other iter types.
+ */
+ if (iov_iter_type(from) != ITER_IOVEC)
+ return -EFAULT;
+
+ while (length && iov_iter_count(from)) {
+ if (i == MAX_SKB_FRAGS)
+ return -EMSGSIZE;
+
+ virt_addr = (size_t)iter_iov_addr(from);
+ niov = net_devmem_get_niov_at(binding, virt_addr, &off, &size);
+ if (!niov)
+ return -EFAULT;
+
+ size = min_t(size_t, size, length);
+ size = min_t(size_t, size, iter_iov_len(from));
+
+ get_netmem(net_iov_to_netmem(niov));
+ skb_add_rx_frag_netmem(skb, i, net_iov_to_netmem(niov), off,
+ size, PAGE_SIZE);
+ iov_iter_advance(from, size);
+ length -= size;
+ i++;
+ }
+
+ return 0;
+}
+
int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb, struct iov_iter *from,
- size_t length)
+ size_t length,
+ struct net_devmem_dmabuf_binding *binding)
{
unsigned long orig_size = skb->truesize;
unsigned long truesize;
@@ -702,6 +744,8 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,

if (msg && msg->msg_ubuf && msg->sg_from_iter)
ret = msg->sg_from_iter(skb, from, length);
+ else if (unlikely(binding))
+ ret = zerocopy_fill_skb_from_devmem(skb, from, length, binding);
else
ret = zerocopy_fill_skb_from_iter(skb, from, length);

@@ -735,7 +779,7 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
if (skb_copy_datagram_from_iter(skb, 0, from, copy))
return -EFAULT;

- return __zerocopy_sg_from_iter(NULL, NULL, skb, from, ~0U);
+ return __zerocopy_sg_from_iter(NULL, NULL, skb, from, ~0U, NULL);
}
EXPORT_SYMBOL(zerocopy_sg_from_iter);

diff --git a/net/core/devmem.c b/net/core/devmem.c
index 0cf3d189f06c..393e30d72dc8 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -17,6 +17,7 @@
#include <net/netdev_rx_queue.h>
#include <net/page_pool/helpers.h>
#include <net/page_pool/memory_provider.h>
+#include <net/sock.h>
#include <trace/events/page_pool.h>

#include "devmem.h"
@@ -54,8 +55,10 @@ static dma_addr_t net_devmem_get_dma_addr(const struct net_iov *niov)
((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
}

-void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
+void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
{
+ struct net_devmem_dmabuf_binding *binding = container_of(wq, typeof(*binding), unbind_w);
+
size_t size, avail;

gen_pool_for_each_chunk(binding->chunk_pool,
@@ -73,8 +76,10 @@ void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
dma_buf_detach(binding->dmabuf, binding->attachment);
dma_buf_put(binding->dmabuf);
xa_destroy(&binding->bound_rxqs);
+ kvfree(binding->tx_vec);
kfree(binding);
}
+EXPORT_SYMBOL(__net_devmem_dmabuf_binding_free);

struct net_iov *
net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
@@ -119,6 +124,13 @@ void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
unsigned long xa_idx;
unsigned int rxq_idx;

+ xa_erase(&net_devmem_dmabuf_bindings, binding->id);
+
+ /* Ensure no tx net_devmem_lookup_dmabuf() are in flight after the
+ * erase.
+ */
+ synchronize_net();
+
if (binding->list.next)
list_del(&binding->list);

@@ -133,8 +145,6 @@ void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
WARN_ON(netdev_rx_queue_restart(binding->dev, rxq_idx));
}

- xa_erase(&net_devmem_dmabuf_bindings, binding->id);
-
net_devmem_dmabuf_binding_put(binding);
}

@@ -197,8 +207,9 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
}

struct net_devmem_dmabuf_binding *
-net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
- struct netlink_ext_ack *extack)
+net_devmem_bind_dmabuf(struct net_device *dev,
+ enum dma_data_direction direction,
+ unsigned int dmabuf_fd, struct netlink_ext_ack *extack)
{
struct net_devmem_dmabuf_binding *binding;
static u32 id_alloc_next;
@@ -241,22 +252,32 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
}

binding->sgt = dma_buf_map_attachment_unlocked(binding->attachment,
- DMA_FROM_DEVICE);
+ direction);
if (IS_ERR(binding->sgt)) {
err = PTR_ERR(binding->sgt);
NL_SET_ERR_MSG(extack, "Failed to map dmabuf attachment");
goto err_detach;
}

+ if (direction == DMA_TO_DEVICE) {
+ binding->tx_vec = kvmalloc_array(dmabuf->size / PAGE_SIZE,
+ sizeof(struct net_iov *),
+ GFP_KERNEL);
+ if (!binding->tx_vec) {
+ err = -ENOMEM;
+ goto err_unmap;
+ }
+ }
+
/* 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));
+ binding->chunk_pool = gen_pool_create(PAGE_SHIFT,
+ dev_to_node(&dev->dev));
if (!binding->chunk_pool) {
err = -ENOMEM;
- goto err_unmap;
+ goto err_tx_vec;
}

virtual = 0;
@@ -301,6 +322,8 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
niov->owner = &owner->area;
page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
net_devmem_get_dma_addr(niov));
+ if (direction == DMA_TO_DEVICE)
+ binding->tx_vec[owner->area.base_virtual / PAGE_SIZE + i] = niov;
}

virtual += len;
@@ -312,6 +335,8 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
gen_pool_for_each_chunk(binding->chunk_pool,
net_devmem_dmabuf_free_chunk_owner, NULL);
gen_pool_destroy(binding->chunk_pool);
+err_tx_vec:
+ kvfree(binding->tx_vec);
err_unmap:
dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt,
DMA_FROM_DEVICE);
@@ -326,6 +351,21 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
return ERR_PTR(err);
}

+struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id)
+{
+ struct net_devmem_dmabuf_binding *binding;
+
+ rcu_read_lock();
+ binding = xa_load(&net_devmem_dmabuf_bindings, id);
+ if (binding) {
+ if (!net_devmem_dmabuf_binding_get(binding))
+ binding = NULL;
+ }
+ rcu_read_unlock();
+
+ return binding;
+}
+
void net_devmem_get_net_iov(struct net_iov *niov)
{
net_devmem_dmabuf_binding_get(net_devmem_iov_binding(niov));
@@ -336,6 +376,53 @@ void net_devmem_put_net_iov(struct net_iov *niov)
net_devmem_dmabuf_binding_put(net_devmem_iov_binding(niov));
}

+struct net_devmem_dmabuf_binding *net_devmem_get_binding(struct sock *sk,
+ unsigned int dmabuf_id)
+{
+ struct net_devmem_dmabuf_binding *binding;
+ struct dst_entry *dst = __sk_dst_get(sk);
+ int err = 0;
+
+ binding = net_devmem_lookup_dmabuf(dmabuf_id);
+ if (!binding || !binding->tx_vec) {
+ err = -EINVAL;
+ goto out_err;
+ }
+
+ /* The dma-addrs in this binding are only reachable to the corresponding
+ * net_device.
+ */
+ if (!dst || !dst->dev || dst->dev->ifindex != binding->dev->ifindex) {
+ err = -ENODEV;
+ goto out_err;
+ }
+
+ return binding;
+
+out_err:
+ if (binding)
+ net_devmem_dmabuf_binding_put(binding);
+
+ return ERR_PTR(err);
+}
+
+struct net_iov *
+net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding,
+ size_t virt_addr, size_t *off, size_t *size)
+{
+ size_t idx;
+
+ if (virt_addr >= binding->dmabuf->size)
+ return NULL;
+
+ idx = virt_addr / PAGE_SIZE;
+
+ *off = virt_addr % PAGE_SIZE;
+ *size = PAGE_SIZE - *off;
+
+ return binding->tx_vec[idx];
+}
+
/*** "Dmabuf devmem memory provider" ***/

int mp_dmabuf_devmem_init(struct page_pool *pool)
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 946f2e015746..67168aae5e5b 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -23,8 +23,9 @@ struct net_devmem_dmabuf_binding {

/* 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.
+ * a ref to keep the binding alive. The page_pool does not release the
+ * ref until all the net_iovs allocated from this binding are released
+ * back to the page_pool.
*
* The binding undos itself and unmaps the underlying dmabuf once all
* those refs are dropped and the binding is no longer desired or in
@@ -32,7 +33,10 @@ struct net_devmem_dmabuf_binding {
*
* net_devmem_get_net_iov() on dmabuf net_iovs will increment this
* reference, making sure that the binding remains alive until all the
- * net_iovs are no longer used.
+ * net_iovs are no longer used. net_iovs allocated from this binding
+ * that are stuck in the TX path for any reason (such as awaiting
+ * retransmits) hold a reference to the binding until the skb holding
+ * them is freed.
*/
refcount_t ref;

@@ -48,6 +52,14 @@ struct net_devmem_dmabuf_binding {
* active.
*/
u32 id;
+
+ /* Array of net_iov pointers for this binding, sorted by virtual
+ * address. This array is convenient to map the virtual addresses to
+ * net_iovs in the TX path.
+ */
+ struct net_iov **tx_vec;
+
+ struct work_struct unbind_w;
};

#if defined(CONFIG_NET_DEVMEM)
@@ -64,14 +76,17 @@ struct dmabuf_genpool_chunk_owner {
dma_addr_t base_dma_addr;
};

-void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding);
+void __net_devmem_dmabuf_binding_free(struct work_struct *wq);
struct net_devmem_dmabuf_binding *
-net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
- struct netlink_ext_ack *extack);
+net_devmem_bind_dmabuf(struct net_device *dev,
+ enum dma_data_direction direction,
+ unsigned int dmabuf_fd, struct netlink_ext_ack *extack);
+struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id);
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 net_devmem_bind_tx_release(struct sock *sk);

static inline struct dmabuf_genpool_chunk_owner *
net_devmem_iov_to_chunk_owner(const struct net_iov *niov)
@@ -100,10 +115,10 @@ static inline unsigned long net_iov_virtual_addr(const struct net_iov *niov)
((unsigned long)net_iov_idx(niov) << PAGE_SHIFT);
}

-static inline void
+static inline bool
net_devmem_dmabuf_binding_get(struct net_devmem_dmabuf_binding *binding)
{
- refcount_inc(&binding->ref);
+ return refcount_inc_not_zero(&binding->ref);
}

static inline void
@@ -112,7 +127,8 @@ 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);
+ INIT_WORK(&binding->unbind_w, __net_devmem_dmabuf_binding_free);
+ schedule_work(&binding->unbind_w);
}

void net_devmem_get_net_iov(struct net_iov *niov);
@@ -123,6 +139,11 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
void net_devmem_free_dmabuf(struct net_iov *ppiov);

bool net_is_devmem_iov(struct net_iov *niov);
+struct net_devmem_dmabuf_binding *
+net_devmem_get_binding(struct sock *sk, unsigned int dmabuf_id);
+struct net_iov *
+net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding, size_t addr,
+ size_t *off, size_t *size);

#else
struct net_devmem_dmabuf_binding;
@@ -140,18 +161,23 @@ static inline void net_devmem_put_net_iov(struct net_iov *niov)
{
}

-static inline void
-__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
+static inline void __net_devmem_dmabuf_binding_free(struct work_struct *wq)
{
}

static inline struct net_devmem_dmabuf_binding *
net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
+ enum dma_data_direction direction,
struct netlink_ext_ack *extack)
{
return ERR_PTR(-EOPNOTSUPP);
}

+static inline struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id)
+{
+ return NULL;
+}
+
static inline void
net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
{
@@ -190,6 +216,19 @@ static inline bool net_is_devmem_iov(struct net_iov *niov)
{
return false;
}
+
+static inline struct net_devmem_dmabuf_binding *
+net_devmem_get_binding(struct sock *sk, unsigned int dmabuf_id)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline struct net_iov *
+net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding, size_t addr,
+ size_t *off, size_t *size)
+{
+ return NULL;
+}
#endif

#endif /* _NET_DEVMEM_H */
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 6e5f2de4d947..6e7cd6a5c177 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -874,7 +874,8 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
goto err_unlock;
}

- binding = net_devmem_bind_dmabuf(netdev, dmabuf_fd, info->extack);
+ binding = net_devmem_bind_dmabuf(netdev, DMA_FROM_DEVICE, dmabuf_fd,
+ info->extack);
if (IS_ERR(binding)) {
err = PTR_ERR(binding);
goto err_unlock;
@@ -931,10 +932,67 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
return err;
}

-/* stub */
int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
{
- return 0;
+ struct net_devmem_dmabuf_binding *binding;
+ struct list_head *sock_binding_list;
+ struct net_device *netdev;
+ u32 ifindex, dmabuf_fd;
+ struct sk_buff *rsp;
+ int err = 0;
+ void *hdr;
+
+ if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_DEV_IFINDEX) ||
+ GENL_REQ_ATTR_CHECK(info, NETDEV_A_DMABUF_FD))
+ 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;
+ }
+
+ binding = net_devmem_bind_dmabuf(netdev, DMA_TO_DEVICE, dmabuf_fd,
+ info->extack);
+ if (IS_ERR(binding)) {
+ err = PTR_ERR(binding);
+ goto err_unlock;
+ }
+
+ list_add(&binding->list, sock_binding_list);
+
+ nla_put_u32(rsp, NETDEV_A_DMABUF_ID, binding->id);
+ genlmsg_end(rsp, hdr);
+
+ rtnl_unlock();
+
+ return genlmsg_reply(rsp, info);
+
+err_unlock:
+ rtnl_unlock();
+err_genlmsg_free:
+ nlmsg_free(rsp);
+ return err;
}

void netdev_nl_sock_priv_init(struct list_head *priv)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ee2d1b769c13..f911f8c6773f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1667,7 +1667,8 @@ void mm_unaccount_pinned_pages(struct mmpin *mmp)
}
EXPORT_SYMBOL_GPL(mm_unaccount_pinned_pages);

-static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
+static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size,
+ bool devmem)
{
struct ubuf_info_msgzc *uarg;
struct sk_buff *skb;
@@ -1682,7 +1683,7 @@ static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
uarg = (void *)skb->cb;
uarg->mmp.user = NULL;

- if (mm_account_pinned_pages(&uarg->mmp, size)) {
+ if (likely(!devmem) && mm_account_pinned_pages(&uarg->mmp, size)) {
kfree_skb(skb);
return NULL;
}
@@ -1705,7 +1706,7 @@ static inline struct sk_buff *skb_from_uarg(struct ubuf_info_msgzc *uarg)
}

struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
- struct ubuf_info *uarg)
+ struct ubuf_info *uarg, bool devmem)
{
if (uarg) {
struct ubuf_info_msgzc *uarg_zc;
@@ -1735,7 +1736,8 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,

next = (u32)atomic_read(&sk->sk_zckey);
if ((u32)(uarg_zc->id + uarg_zc->len) == next) {
- if (mm_account_pinned_pages(&uarg_zc->mmp, size))
+ if (likely(!devmem) &&
+ mm_account_pinned_pages(&uarg_zc->mmp, size))
return NULL;
uarg_zc->len++;
uarg_zc->bytelen = bytelen;
@@ -1750,7 +1752,7 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
}

new_alloc:
- return msg_zerocopy_alloc(sk, size);
+ return msg_zerocopy_alloc(sk, size, devmem);
}
EXPORT_SYMBOL_GPL(msg_zerocopy_realloc);

@@ -1854,7 +1856,8 @@ EXPORT_SYMBOL_GPL(msg_zerocopy_ubuf_ops);

int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
struct msghdr *msg, int len,
- struct ubuf_info *uarg)
+ struct ubuf_info *uarg,
+ struct net_devmem_dmabuf_binding *binding)
{
int err, orig_len = skb->len;

@@ -1873,7 +1876,8 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
return -EEXIST;
}

- err = __zerocopy_sg_from_iter(msg, sk, skb, &msg->msg_iter, len);
+ err = __zerocopy_sg_from_iter(msg, sk, skb, &msg->msg_iter, len,
+ binding);
if (err == -EFAULT || (err == -EMSGSIZE && skb->len == orig_len)) {
struct sock *save_sk = skb->sk;

diff --git a/net/core/sock.c b/net/core/sock.c
index a0598518ce89..e1dae98b55ca 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3012,6 +3012,12 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
if (!sk_set_prio_allowed(sk, *(u32 *)CMSG_DATA(cmsg)))
return -EPERM;
sockc->priority = *(u32 *)CMSG_DATA(cmsg);
+ break;
+ case SCM_DEVMEM_DMABUF:
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof(u32)))
+ return -EINVAL;
+ sockc->dmabuf_id = *(u32 *)CMSG_DATA(cmsg);
+
break;
default:
return -EINVAL;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index ea7a260bec8a..7d8a5f3fae9b 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1015,7 +1015,8 @@ static int __ip_append_data(struct sock *sk,
uarg = msg->msg_ubuf;
}
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
- uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+ uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb),
+ false);
if (!uarg)
return -ENOBUFS;
extra_uref = !skb_zcopy(skb); /* only ref on new uarg */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 46951e749308..8564b0e66bbd 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1059,6 +1059,7 @@ int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,

int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
{
+ struct net_devmem_dmabuf_binding *binding = NULL;
struct tcp_sock *tp = tcp_sk(sk);
struct ubuf_info *uarg = NULL;
struct sk_buff *skb;
@@ -1066,11 +1067,24 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
int flags, err, copied = 0;
int mss_now = 0, size_goal, copied_syn = 0;
int process_backlog = 0;
+ bool sockc_valid = true;
int zc = 0;
long timeo;

flags = msg->msg_flags;

+ sockc = (struct sockcm_cookie){ .tsflags = READ_ONCE(sk->sk_tsflags),
+ .dmabuf_id = 0 };
+ if (msg->msg_controllen) {
+ err = sock_cmsg_send(sk, msg, &sockc);
+ if (unlikely(err))
+ /* Don't return error until MSG_FASTOPEN has been
+ * processed; that may succeed even if the cmsg is
+ * invalid.
+ */
+ sockc_valid = false;
+ }
+
if ((flags & MSG_ZEROCOPY) && size) {
if (msg->msg_ubuf) {
uarg = msg->msg_ubuf;
@@ -1078,7 +1092,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
zc = MSG_ZEROCOPY;
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
skb = tcp_write_queue_tail(sk);
- uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
+ uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb),
+ sockc_valid && !!sockc.dmabuf_id);
if (!uarg) {
err = -ENOBUFS;
goto out_err;
@@ -1087,12 +1102,27 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
zc = MSG_ZEROCOPY;
else
uarg_to_msgzc(uarg)->zerocopy = 0;
+
+ if (sockc_valid && sockc.dmabuf_id) {
+ binding = net_devmem_get_binding(sk, sockc.dmabuf_id);
+ if (IS_ERR(binding)) {
+ err = PTR_ERR(binding);
+ binding = NULL;
+ goto out_err;
+ }
+ }
}
} else if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES) && size) {
if (sk->sk_route_caps & NETIF_F_SG)
zc = MSG_SPLICE_PAGES;
}

+ if (sockc_valid && sockc.dmabuf_id &&
+ (!(flags & MSG_ZEROCOPY) || !sock_flag(sk, SOCK_ZEROCOPY))) {
+ err = -EINVAL;
+ goto out_err;
+ }
+
if (unlikely(flags & MSG_FASTOPEN ||
inet_test_bit(DEFER_CONNECT, sk)) &&
!tp->repair) {
@@ -1131,14 +1161,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
/* 'common' sending to sendq */
}

- sockc = (struct sockcm_cookie) { .tsflags = READ_ONCE(sk->sk_tsflags)};
- if (msg->msg_controllen) {
- err = sock_cmsg_send(sk, msg, &sockc);
- if (unlikely(err)) {
- err = -EINVAL;
- goto out_err;
- }
- }
+ if (!sockc_valid)
+ goto out_err;

/* This should be in poll */
sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -1256,7 +1280,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
goto wait_for_space;
}

- err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg);
+ err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg,
+ binding);
if (err == -EMSGSIZE || err == -EEXIST) {
tcp_mark_push(tp, skb);
goto new_segment;
@@ -1337,6 +1362,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
/* msg->msg_ubuf is pinned by the caller so we don't take extra refs */
if (uarg && !msg->msg_ubuf)
net_zcopy_put(uarg);
+ if (binding)
+ net_devmem_dmabuf_binding_put(binding);
return copied + copied_syn;

do_error:
@@ -1354,6 +1381,9 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
sk->sk_write_space(sk);
tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
}
+ if (binding)
+ net_devmem_dmabuf_binding_put(binding);
+
return err;
}
EXPORT_SYMBOL_GPL(tcp_sendmsg_locked);
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index d577bf2f3053..e9e752f08f87 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1523,7 +1523,8 @@ static int __ip6_append_data(struct sock *sk,
uarg = msg->msg_ubuf;
}
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
- uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+ uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb),
+ false);
if (!uarg)
return -ENOBUFS;
extra_uref = !skb_zcopy(skb); /* only ref on new uarg */
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 7f7de6d88096..6e7b727c781c 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -87,7 +87,7 @@ static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,

uarg = msg_zerocopy_realloc(sk_vsock(vsk),
iter->count,
- NULL);
+ NULL, false);
if (!uarg)
return -1;

@@ -107,8 +107,7 @@ static int virtio_transport_fill_skb(struct sk_buff *skb,
{
if (zcopy)
return __zerocopy_sg_from_iter(info->msg, NULL, skb,
- &info->msg->msg_iter,
- len);
+ &info->msg->msg_iter, len, NULL);

return memcpy_from_msg(skb_put(skb, len), info->msg, len);
}
--
2.49.0.rc0.332.g42c0ae87b1-goog