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Date: Mon, 23 Oct 2023 10:28:33 +0200
From: Magnus Karlsson <magnus.karlsson@...il.com>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, haoluo@...gle.com,
jolsa@...nel.org, kuba@...nel.org, toke@...nel.org, willemb@...gle.com,
dsahern@...nel.org, magnus.karlsson@...el.com, bjorn@...nel.org,
maciej.fijalkowski@...el.com, hawk@...nel.org, yoong.siang.song@...el.com,
netdev@...r.kernel.org, xdp-hints@...-project.net
Subject: Re: [PATCH bpf-next v4 01/11] xsk: Support tx_metadata_len
On Thu, 19 Oct 2023 at 19:50, Stanislav Fomichev <sdf@...gle.com> wrote:
>
> For zerocopy mode, tx_desc->addr can point to the arbitrary offset
nit: the -> an
> and carry some TX metadata in the headroom. For copy mode, there
> is no way currently to populate skb metadata.
>
> Introduce new tx_metadata_len umem config option that indicates how many
> bytes to treat as metadata. Metadata bytes come prior to tx_desc address
> (same as in RX case).
>
> The size of the metadata has the same constraints as XDP:
> - less than 256 bytes
> - 4-byte aligned
> - non-zero
>
> This data is not interpreted in any way right now.
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
> include/net/xdp_sock.h | 1 +
> include/net/xsk_buff_pool.h | 1 +
> include/uapi/linux/if_xdp.h | 1 +
> net/xdp/xdp_umem.c | 4 ++++
> net/xdp/xsk.c | 12 +++++++++++-
> net/xdp/xsk_buff_pool.c | 1 +
> net/xdp/xsk_queue.h | 17 ++++++++++-------
> tools/include/uapi/linux/if_xdp.h | 1 +
> 8 files changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> index 7dd0df2f6f8e..5ae88a00f34a 100644
> --- a/include/net/xdp_sock.h
> +++ b/include/net/xdp_sock.h
> @@ -30,6 +30,7 @@ struct xdp_umem {
> struct user_struct *user;
> refcount_t users;
> u8 flags;
> + u8 tx_metadata_len;
> bool zc;
> struct page **pgs;
> int id;
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index b0bdff26fc88..1985ffaf9b0c 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -77,6 +77,7 @@ struct xsk_buff_pool {
> u32 chunk_size;
> u32 chunk_shift;
> u32 frame_len;
> + u8 tx_metadata_len; /* inherited from umem */
> u8 cached_need_wakeup;
> bool uses_need_wakeup;
> bool dma_need_sync;
> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
> index 8d48863472b9..2ecf79282c26 100644
> --- a/include/uapi/linux/if_xdp.h
> +++ b/include/uapi/linux/if_xdp.h
> @@ -76,6 +76,7 @@ struct xdp_umem_reg {
> __u32 chunk_size;
> __u32 headroom;
> __u32 flags;
> + __u32 tx_metadata_len;
> };
>
> struct xdp_statistics {
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index 06cead2b8e34..333f3d53aad4 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -199,6 +199,9 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
> if (headroom >= chunk_size - XDP_PACKET_HEADROOM)
> return -EINVAL;
>
> + if (mr->tx_metadata_len > 256 || mr->tx_metadata_len % 4)
> + return -EINVAL;
Should be >= 256 since the final internal destination is a u8 and the
documentation says "should be less than 256 bytes".
> +
> umem->size = size;
> umem->headroom = headroom;
> umem->chunk_size = chunk_size;
> @@ -207,6 +210,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
> umem->pgs = NULL;
> umem->user = NULL;
> umem->flags = mr->flags;
> + umem->tx_metadata_len = mr->tx_metadata_len;
>
> INIT_LIST_HEAD(&umem->xsk_dma_list);
> refcount_set(&umem->users, 1);
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index ba070fd37d24..ba4c77a24a83 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -1265,6 +1265,14 @@ struct xdp_umem_reg_v1 {
> __u32 headroom;
> };
>
> +struct xdp_umem_reg_v2 {
> + __u64 addr; /* Start of packet data area */
> + __u64 len; /* Length of packet data area */
> + __u32 chunk_size;
> + __u32 headroom;
> + __u32 flags;
> +};
> +
> static int xsk_setsockopt(struct socket *sock, int level, int optname,
> sockptr_t optval, unsigned int optlen)
> {
> @@ -1308,8 +1316,10 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
>
> if (optlen < sizeof(struct xdp_umem_reg_v1))
> return -EINVAL;
> - else if (optlen < sizeof(mr))
> + else if (optlen < sizeof(struct xdp_umem_reg_v2))
> mr_size = sizeof(struct xdp_umem_reg_v1);
> + else if (optlen < sizeof(mr))
> + mr_size = sizeof(struct xdp_umem_reg_v2);
>
> if (copy_from_sockptr(&mr, optval, mr_size))
> return -EFAULT;
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> index 49cb9f9a09be..386eddcdf837 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -85,6 +85,7 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
> XDP_PACKET_HEADROOM;
> pool->umem = umem;
> pool->addrs = umem->addrs;
> + pool->tx_metadata_len = umem->tx_metadata_len;
> INIT_LIST_HEAD(&pool->free_list);
> INIT_LIST_HEAD(&pool->xskb_list);
> INIT_LIST_HEAD(&pool->xsk_tx_list);
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index 13354a1e4280..c74a1372bcb9 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -143,15 +143,17 @@ static inline bool xp_unused_options_set(u32 options)
> static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
> struct xdp_desc *desc)
> {
> - u64 offset = desc->addr & (pool->chunk_size - 1);
> + u64 addr = desc->addr - pool->tx_metadata_len;
> + u64 len = desc->len + pool->tx_metadata_len;
> + u64 offset = addr & (pool->chunk_size - 1);
>
> if (!desc->len)
> return false;
>
> - if (offset + desc->len > pool->chunk_size)
> + if (offset + len > pool->chunk_size)
> return false;
>
> - if (desc->addr >= pool->addrs_cnt)
> + if (addr >= pool->addrs_cnt)
> return false;
>
> if (xp_unused_options_set(desc->options))
> @@ -162,16 +164,17 @@ static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
> static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
> struct xdp_desc *desc)
> {
> - u64 addr = xp_unaligned_add_offset_to_addr(desc->addr);
> + u64 addr = xp_unaligned_add_offset_to_addr(desc->addr) - pool->tx_metadata_len;
> + u64 len = desc->len + pool->tx_metadata_len;
>
> if (!desc->len)
> return false;
>
> - if (desc->len > pool->chunk_size)
> + if (len > pool->chunk_size)
> return false;
>
> - if (addr >= pool->addrs_cnt || addr + desc->len > pool->addrs_cnt ||
> - xp_desc_crosses_non_contig_pg(pool, addr, desc->len))
> + if (addr >= pool->addrs_cnt || addr + len > pool->addrs_cnt ||
> + xp_desc_crosses_non_contig_pg(pool, addr, len))
> return false;
>
> if (xp_unused_options_set(desc->options))
> diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
> index 73a47da885dc..34411a2e5b6c 100644
> --- a/tools/include/uapi/linux/if_xdp.h
> +++ b/tools/include/uapi/linux/if_xdp.h
> @@ -76,6 +76,7 @@ struct xdp_umem_reg {
> __u32 chunk_size;
> __u32 headroom;
> __u32 flags;
> + __u32 tx_metadata_len;
> };
>
> struct xdp_statistics {
> --
> 2.42.0.655.g421f12c284-goog
>
>
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