Mina Almasry wrote:
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.
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
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 | 15 +++- include/net/sock.h | 1 + include/uapi/linux/uio.h | 6 +- net/core/datagram.c | 41 ++++++++++- net/core/devmem.c | 97 +++++++++++++++++++++++-- net/core/devmem.h | 42 ++++++++++- net/core/netdev-genl.c | 64 +++++++++++++++- net/core/skbuff.c | 6 +- net/core/sock.c | 8 ++ net/ipv4/tcp.c | 36 ++++++--- net/vmw_vsock/virtio_transport_common.c | 3 +- 11 files changed, 285 insertions(+), 34 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index bb2b751d274a..3ff8f568c382 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1711,9 +1711,12 @@ 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,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 8036b3b79cd8..09eb918525b6 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1822,6 +1822,7 @@ 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/include/uapi/linux/uio.h b/include/uapi/linux/uio.h index 649739e0c404..866bd5dfe39f 100644 --- a/include/uapi/linux/uio.h +++ b/include/uapi/linux/uio.h @@ -38,10 +38,14 @@ struct dmabuf_token { __u32 token_count; }; +struct dmabuf_tx_cmsg {
- __u32 dmabuf_id;
+};
Why a wrapper struct instead of just __u32?