On 12/20, Stanislav Fomichev wrote:
> On 12/21, Mina Almasry wrote:
> > Augment dmabuf binding to be able to handle TX. Additional to all the RX
> > binding, we also create tx_vec and tx_iter 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,
> > and the offset into 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 look up the dmabuf to send from by id, then 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.
> >
> > Based on work by Stanislav Fomichev <[email protected]>. 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 <[email protected]>
> > Signed-off-by: Kaiyuan Zhang <[email protected]>
> > Signed-off-by: Mina Almasry <[email protected]>
> >
> > ---
> > include/linux/skbuff.h | 13 +++-
> > include/net/sock.h | 2 +
> > include/uapi/linux/uio.h | 5 ++
> > net/core/datagram.c | 40 ++++++++++-
> > net/core/devmem.c | 91 +++++++++++++++++++++++--
> > net/core/devmem.h | 40 +++++++++--
> > net/core/netdev-genl.c | 65 +++++++++++++++++-
> > net/core/skbuff.c | 8 ++-
> > net/core/sock.c | 9 +++
> > net/ipv4/tcp.c | 36 +++++++---
> > net/vmw_vsock/virtio_transport_common.c | 4 +-
> > 11 files changed, 281 insertions(+), 32 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index bb2b751d274a..e90dc0c4d542 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -1711,9 +1711,10 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock
> > *sk, size_t size,
> >
> > 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, bool is_devmem);
> >
> > int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
> > struct iov_iter *from, size_t length);
> > @@ -1721,12 +1722,14 @@ 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,
> > + false);
> > }
> >
> > 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 +3700,10 @@ 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 d4bdd3286e03..75bd580fe9c6 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -1816,6 +1816,8 @@ struct sockcm_cookie {
> > u32 tsflags;
> > u32 ts_opt_id;
> > u32 priority;
> > + u32 dmabuf_id;
> > + u64 dmabuf_offset;
> > };
> >
> > static inline void sockcm_init(struct sockcm_cookie *sockc,
> > diff --git a/include/uapi/linux/uio.h b/include/uapi/linux/uio.h
> > index 649739e0c404..41490cde95ad 100644
> > --- a/include/uapi/linux/uio.h
> > +++ b/include/uapi/linux/uio.h
> > @@ -38,6 +38,11 @@ struct dmabuf_token {
> > __u32 token_count;
> > };
> >
> > +struct dmabuf_tx_cmsg {
> > + __u32 dmabuf_id;
> > + __u64 dmabuf_offset;
> > +};
> > +
> > /*
> > * UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
> > */
> > diff --git a/net/core/datagram.c b/net/core/datagram.c
> > index f0693707aece..3b09995db894 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 +694,41 @@ int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
> > return 0;
> > }
> >
> > +static int zerocopy_fill_skb_from_devmem(struct sk_buff *skb,
> > + struct msghdr *msg,
> > + struct iov_iter *from, int length)
> > +{
> > + int i = skb_shinfo(skb)->nr_frags;
> > + int orig_length = length;
> > + netmem_ref netmem;
> > + size_t size;
> > +
> > + while (length && iov_iter_count(from)) {
> > + if (i == MAX_SKB_FRAGS)
> > + return -EMSGSIZE;
> > +
> > + size = min_t(size_t, iter_iov_len(from), length);
> > + if (!size)
> > + return -EFAULT;
> > +
> > + netmem = net_iov_to_netmem(iter_iov(from)->iov_base);
> > + get_netmem(netmem);
> > + skb_add_rx_frag_netmem(skb, i, netmem, from->iov_offset, size,
> > + PAGE_SIZE);
> > +
> > + iov_iter_advance(from, size);
> > + length -= size;
> > + i++;
> > + }
> > +
> > + iov_iter_advance(&msg->msg_iter, orig_length);
> > +
> > + 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, bool is_devmem)
> > {
> > unsigned long orig_size = skb->truesize;
> > unsigned long truesize;
> > @@ -702,6 +736,8 @@ 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(is_devmem))
> > + ret = zerocopy_fill_skb_from_devmem(skb, msg, from, length);
> > else
> > ret = zerocopy_fill_skb_from_iter(skb, from, length);
> >
> > @@ -735,7 +771,7 @@ 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 f7e06a8cba01..81f1b715cfa6 100644
> > --- a/net/core/devmem.c
> > +++ b/net/core/devmem.c
> > @@ -15,6 +15,7 @@
> > #include <net/netdev_queues.h>
> > #include <net/netdev_rx_queue.h>
> > #include <net/page_pool/helpers.h>
> > +#include <net/sock.h>
> > #include <trace/events/page_pool.h>
> >
> > #include "devmem.h"
> > @@ -63,8 +64,10 @@ 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);
> > + kfree(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)
> > @@ -109,6 +112,13 @@ 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);
> >
> > @@ -122,8 +132,6 @@ 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);
> > }
> >
> > @@ -174,8 +182,9 @@ 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;
> > @@ -183,6 +192,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned
> > int dmabuf_fd,
> > struct dma_buf *dmabuf;
> > unsigned int sg_idx, i;
> > unsigned long virtual;
> > + struct iovec *iov;
> > int err;
> >
> > dmabuf = dma_buf_get(dmabuf_fd);
> > @@ -218,13 +228,19 @@ 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 (!binding->sgt || binding->sgt->nents == 0) {
> > + err = -EINVAL;
> > + NL_SET_ERR_MSG(extack, "Empty 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...
> > @@ -236,6 +252,19 @@ net_devmem_bind_dmabuf(struct net_device *dev,
> > unsigned int dmabuf_fd,
> > goto err_unmap;
> > }
> >
> > + if (direction == DMA_TO_DEVICE) {
> > + virtual = 0;
> > + for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx)
> > + virtual += sg_dma_len(sg);
> > +
> > + binding->tx_vec = kcalloc(virtual / PAGE_SIZE + 1,
> > + sizeof(struct iovec), GFP_KERNEL);
> > + if (!binding->tx_vec) {
> > + 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);
> > @@ -277,11 +306,21 @@ net_devmem_bind_dmabuf(struct net_device *dev,
> > unsigned int dmabuf_fd,
> > niov->owner = owner;
> > page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov),
> >
> > net_devmem_get_dma_addr(niov));
> > +
> > + if (direction == DMA_TO_DEVICE) {
> > + iov = &binding->tx_vec[virtual / PAGE_SIZE + i];
> > + iov->iov_base = niov;
> > + iov->iov_len = PAGE_SIZE;
> > + }
> > }
> >
> > virtual += len;
> > }
> >
> > + if (direction == DMA_TO_DEVICE)
> > + iov_iter_init(&binding->tx_iter, WRITE, binding->tx_vec,
> > + virtual / PAGE_SIZE + 1, virtual);
> > +
> > return binding;
> >
> > err_free_chunks:
> > @@ -302,6 +341,21 @@ 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 dev_dmabuf_uninstall(struct net_device *dev)
> > {
> > struct net_devmem_dmabuf_binding *binding;
> > @@ -332,6 +386,33 @@ void net_devmem_put_net_iov(struct net_iov *niov)
> > net_devmem_dmabuf_binding_put(niov->owner->binding);
> > }
> >
> > +struct net_devmem_dmabuf_binding *
> > +net_devmem_get_sockc_binding(struct sock *sk, struct sockcm_cookie *sockc)
> > +{
> > + struct net_devmem_dmabuf_binding *binding;
> > + int err = 0;
> > +
> > + binding = net_devmem_lookup_dmabuf(sockc->dmabuf_id);
> > + if (!binding || !binding->tx_vec) {
> > + err = -EINVAL;
> > + goto out_err;
> > + }
> > +
> > + if (sock_net(sk) != dev_net(binding->dev)) {
> > + err = -ENODEV;
> > + goto out_err;
> > + }
> > +
> > + iov_iter_advance(&binding->tx_iter, sockc->dmabuf_offset);
> > + return binding;
> > +
> > +out_err:
> > + if (binding)
> > + net_devmem_dmabuf_binding_put(binding);
> > +
> > + return ERR_PTR(err);
> > +}
> > +
> > /*** "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 54e30fea80b3..f923c77d9c45 100644
> > --- a/net/core/devmem.h
> > +++ b/net/core/devmem.h
> > @@ -11,6 +11,8 @@
> > #define _NET_DEVMEM_H
> >
> > struct netlink_ext_ack;
> > +struct sockcm_cookie;
> > +struct sock;
> >
> > struct net_devmem_dmabuf_binding {
> > struct dma_buf *dmabuf;
> > @@ -27,6 +29,10 @@ struct net_devmem_dmabuf_binding {
> > * 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.
> > + *
> > + * net_devmem_get_net_iov() on dmabuf net_iovs will increment this
> > + * reference, making sure that that the binding remains alive until all
> > + * the net_iovs are no longer used.
> > */
> > refcount_t ref;
> >
> > @@ -42,6 +48,10 @@ struct net_devmem_dmabuf_binding {
> > * active.
> > */
> > u32 id;
> > +
> > + /* iov_iter representing all possible net_iov chunks in the dmabuf. */
> > + struct iov_iter tx_iter;
> > + struct iovec *tx_vec;
> > };
> >
> > #if defined(CONFIG_NET_DEVMEM)
> > @@ -66,8 +76,10 @@ struct dmabuf_genpool_chunk_owner {
> >
> > 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);
> > +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,
> > @@ -104,10 +116,10 @@ static inline u32 net_iov_binding_id(const struct
> > net_iov *niov)
> > return net_iov_owner(niov)->binding->id;
> > }
> >
> > -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
> > @@ -126,6 +138,9 @@ struct net_iov *
> > net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
> > void net_devmem_free_dmabuf(struct net_iov *ppiov);
> >
> > +struct net_devmem_dmabuf_binding *
> > +net_devmem_get_sockc_binding(struct sock *sk, struct sockcm_cookie *sockc);
> > +
> > #else
> > struct net_devmem_dmabuf_binding;
> >
> > @@ -144,11 +159,17 @@ __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,
> > + 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)
> > {
> > @@ -186,6 +207,17 @@ static inline u32 net_iov_binding_id(const struct
> > net_iov *niov)
> > {
> > return 0;
> > }
> > +
> > +static inline void
> > +net_devmem_dmabuf_binding_put(struct net_devmem_dmabuf_binding *binding)
> > +{
> > +}
> > +
> > +static inline struct net_devmem_dmabuf_binding *
> > +net_devmem_get_sockc_binding(struct sock *sk, struct sockcm_cookie *sockc)
> > +{
> > + return ERR_PTR(-EOPNOTSUPP);
> > +}
> > #endif
> >
> > #endif /* _NET_DEVMEM_H */
> > diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> > index 00d3d5851487..b9928bac94da 100644
> > --- a/net/core/netdev-genl.c
> > +++ b/net/core/netdev-genl.c
> > @@ -850,7 +850,8 @@ 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;
> > @@ -907,10 +908,68 @@ 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);
> > +
> > + 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)
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 815245d5c36b..eb6b41a32524 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -1882,8 +1882,10 @@ 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)
> > {
> > + struct iov_iter *from = binding ? &binding->tx_iter : &msg->msg_iter;
>
> For tx, I feel like this needs a copy of binding->tx_iter:
>
> struct iov_iter tx_iter = binding->tx_iter;
> struct iov_iter *from = binding ? &tx_iter : &msg->msg_iter;
>
> Or something similar (rewind?). The tx_iter is advanced in
> zerocopy_fill_skb_from_devmem but never reset back it seems (or I'm
> missing something). In you case, if you call sendmsg twice with the same
> offset, the second one will copy from 2*offset.
Can confirm that it's broken. We should probably have a mode in ncdevmem
to call sendmsg with the fixed sized chunks, something like this:
@@ -912,7 +916,11 @@ static int do_client(struct memory_buffer *mem)
line_size, off);
iov.iov_base = NULL;
- iov.iov_len = line_size;
+ iov.iov_len = line_size <= 4096 ?: 4096;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
@@ -933,6 +941,8 @@ static int do_client(struct memory_buffer *mem)
ret = sendmsg(socket_fd, &msg, MSG_ZEROCOPY);
if (ret < 0)
error(1, errno, "Failed sendmsg");
+ if (ret == 0)
+ break;
fprintf(stderr, "sendmsg_ret=%d\n", ret);
I can put it on my todo to extend the selftests..
