On 03/08, 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.
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);@@ -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);
One thing forgot to mention: we should probably do the same for the allocation path? Move the binding->id allocation to the end of the routine to make sure we 'post' fully initialized bindings? Otherwise, net_devmem_bind_dmabuf migh race with the sendmsg?