RE: [PATCH net v3 2/3] xsk: honor XDP_TX_METADATA in zero-copy path

> -----Original Message-----
> From: Stanislav Fomichev <[email protected]>
> Sent: Wednesday, August 19, 2026 6:06 PM
> To: [email protected]
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; Nguyen, Anthony L <[email protected]>;
> Kitszel, Przemyslaw <[email protected]>;
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]; Lobakin,
> Aleksander <[email protected]>; [email protected]; Karlsson,
> Magnus <[email protected]>; Fijalkowski, Maciej
> <[email protected]>; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; Song, Yoong Siang <[email protected]>;
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]
> Subject: [PATCH net v3 2/3] xsk: honor XDP_TX_METADATA in zero-copy
> path
> 
> The zero-copy path reads TX metadata whenever the UMEM has metadata
> space, even if the descriptor does not set XDP_TX_METADATA. Pass
> descriptor options through the metadata helpers and ignore metadata
> unless the option is set.
> 
> This does not fix the existing per-WQE metadata handling for mlx5
> MPWQEs.
> Only the descriptor that starts a session passes through
> xsk_tx_metadata_request() and configures offload state shared by the
> batch.
> Metadata on descriptors joining an open session is therefore not
> validated and does not configure its requested offloads. In addition,
> a non-NULL metadata pointer from such a descriptor is treated as a
> timestamp completion request even when XDP_TXMD_FLAGS_TIMESTAMP is not
> set, so its metadata union can be overwritten with an unrequested
> timestamp. Fixing mixed metadata states within one MPWQE requires a
> separate change.
> 
> Fixes: 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload
> support")
> Reviewed-by: Alexander Lobakin <[email protected]>
> Signed-off-by: Stanislav Fomichev <[email protected]>
> ---
>  drivers/net/ethernet/intel/igc/igc_main.c     |  3 ++-
>  .../ethernet/mellanox/mlx5/core/en/xsk/tx.c   |  2 +-
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c |  3 ++-
>  include/net/libeth/xsk.h                      |  2 +-
>  include/net/xdp_sock_drv.h                    | 22 +++++++++++-------
> -
>  include/net/xsk_buff_pool.h                   |  3 ++-
>  net/xdp/xsk_buff_pool.c                       |  7 ++++--
>  7 files changed, 26 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> b/drivers/net/ethernet/intel/igc/igc_main.c
> index 39043d8ca1bf..59067939a586 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -3074,7 +3074,8 @@ static void igc_xdp_xmit_zc(struct igc_ring
> *ring)
>  		olinfo_status = xdp_desc.len << IGC_ADVTXD_PAYLEN_SHIFT;
> 
>  		dma = xsk_buff_raw_get_dma(pool, xdp_desc.addr);
> -		meta = xsk_buff_get_metadata(pool, xdp_desc.addr);
> +		meta = xsk_buff_get_metadata(pool, xdp_desc.addr,
> +					     xdp_desc.options);
>  		xsk_buff_raw_dma_sync_for_device(pool, dma,
> xdp_desc.len);
>  		bi = &ring->tx_buffer_info[ntu];
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
> b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
> index 3d19dad8f868..d194eeddd7b5 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
> @@ -99,7 +99,7 @@ bool mlx5e_xsk_tx(struct mlx5e_xdpsq *sq, unsigned
> int budget)
>  		xdptxd.dma_addr = xsk_buff_raw_get_dma(pool, desc.addr);
>  		xdptxd.data = xsk_buff_raw_get_data(pool, desc.addr);
>  		xdptxd.len = desc.len;
> -		meta = xsk_buff_get_metadata(pool, desc.addr);
> +		meta = xsk_buff_get_metadata(pool, desc.addr,
> desc.options);
> 
>  		xsk_buff_raw_dma_sync_for_device(pool, xdptxd.dma_addr,
> xdptxd.len);
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index a71f0df26378..62de03e65a90 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2719,7 +2719,8 @@ static bool stmmac_xdp_xmit_zc(struct
> stmmac_priv *priv, u32 queue, u32 budget)
> 
>  		tx_desc = stmmac_get_tx_desc(priv, tx_q, entry);
>  		dma_addr = xsk_buff_raw_get_dma(pool, xdp_desc.addr);
> -		meta = xsk_buff_get_metadata(pool, xdp_desc.addr);
> +		meta = xsk_buff_get_metadata(pool, xdp_desc.addr,
> +					     xdp_desc.options);
>  		xsk_buff_raw_dma_sync_for_device(pool, dma_addr,
> xdp_desc.len);
> 
>  		/* To return XDP buffer to XSK pool, we simple call diff
> --git a/include/net/libeth/xsk.h b/include/net/libeth/xsk.h index
> 5dcc0d7f65b7..a452b7828ce4 100644
> --- a/include/net/libeth/xsk.h
> +++ b/include/net/libeth/xsk.h
> @@ -196,7 +196,7 @@ __libeth_xsk_xmit_fill_buf_md(const struct
> xdp_desc *xdesc,
>  	struct libeth_xdp_tx_desc desc;
>  	struct xdp_desc_ctx ctx;
> 
> -	ctx = xsk_buff_raw_get_ctx(sq->pool, xdesc->addr);
> +	ctx = xsk_buff_raw_get_ctx(sq->pool, xdesc->addr, xdesc-
> >options);
>  	desc = (typeof(desc)){
>  		.addr	= ctx.dma,
>  		__libeth_xdp_tx_len(xdesc->len),
> diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
> index b344789f5df8..d94aeb506379 100644
> --- a/include/net/xdp_sock_drv.h
> +++ b/include/net/xdp_sock_drv.h
> @@ -240,6 +240,7 @@ static inline void *xsk_buff_raw_get_data(struct
> xsk_buff_pool *pool, u64 addr)
>   * xsk_buff_raw_get_ctx - get &xdp_desc context
>   * @pool: XSk buff pool desc address belongs to
>   * @addr: desc address (from userspace)
> + * @options: desc options (from userspace)
>   *
>   * Wrapper for xp_raw_get_ctx() to be used in drivers, see its kdoc
> for
>   * details.
> @@ -248,9 +249,9 @@ static inline void *xsk_buff_raw_get_data(struct
> xsk_buff_pool *pool, u64 addr)
>   * pointer, if it is present (initialized to %NULL otherwise).
>   */
>  static inline struct xdp_desc_ctx
> -xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr)
> +xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr, u32
> +options)
>  {
> -	return xp_raw_get_ctx(pool, addr);
> +	return xp_raw_get_ctx(pool, addr, options);
>  }
> 
>  #define XDP_TXMD_FLAGS_VALID ( \
> @@ -318,18 +319,20 @@ xsk_tx_metadata_request(const struct
> xsk_buff_pool *pool,  }
> 
>  static inline struct xsk_tx_metadata *
> -__xsk_buff_get_metadata(const struct xsk_buff_pool *pool, void *data)
> +__xsk_buff_get_metadata(const struct xsk_buff_pool *pool, void *data,
> +			unsigned int options)
>  {
> -	if (!pool->tx_metadata_len)
> +	if (!pool->tx_metadata_len || !(options & XDP_TX_METADATA))
>  		return NULL;
> 
>  	return data - pool->tx_metadata_len;
>  }
> 
>  static inline struct xsk_tx_metadata *
> -xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr)
> +xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr, u32
> +options)
>  {
> -	return __xsk_buff_get_metadata(pool, xp_raw_get_data(pool,
> addr));
> +	return __xsk_buff_get_metadata(pool, xp_raw_get_data(pool,
> addr),
> +				       options);
>  }
> 
>  static inline void xsk_buff_dma_sync_for_cpu(struct xdp_buff *xdp) @@
> -510,7 +513,7 @@ static inline void *xsk_buff_raw_get_data(struct
> xsk_buff_pool *pool, u64 addr)  }
> 
>  static inline struct xdp_desc_ctx
> -xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr)
> +xsk_buff_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr, u32
> +options)
>  {
>  	return (struct xdp_desc_ctx){ };
>  }
> @@ -530,13 +533,14 @@ xsk_tx_metadata_request(const struct
> xsk_buff_pool *pool,  }
> 
>  static inline struct xsk_tx_metadata *
> -__xsk_buff_get_metadata(const struct xsk_buff_pool *pool, void *data)
> +__xsk_buff_get_metadata(const struct xsk_buff_pool *pool, void *data,
> +			unsigned int options)
>  {
>  	return NULL;
>  }
> 
>  static inline struct xsk_tx_metadata *
> -xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr)
> +xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr, u32
> +options)
>  {
>  	return NULL;
>  }
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index 2bb1d122b1bc..a7df573784fd 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -154,7 +154,8 @@ struct xdp_desc_ctx {
>  	struct xsk_tx_metadata *meta;
>  };
> 
> -struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool,
> u64 addr);
> +struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool,
> u64 addr,
> +				   u32 options);
> 
>  static inline dma_addr_t xp_get_dma(struct xdp_buff_xsk *xskb)  {
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c index
> 78c14f106395..9d2d94f1fb75 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -763,6 +763,7 @@ EXPORT_SYMBOL(xp_raw_get_dma);
>   * xp_raw_get_ctx - get &xdp_desc context
>   * @pool: XSk buff pool desc address belongs to
>   * @addr: desc address (from userspace)
> + * @options: desc options (from userspace)
>   *
>   * Helper for getting desc's DMA address and metadata pointer, if
> present.
>   * Saves one call on hotpath and double calculation of the actual
> address.
> @@ -771,14 +772,16 @@ EXPORT_SYMBOL(xp_raw_get_dma);
>   * Return: new &xdp_desc_ctx struct containing desc's DMA address and
> metadata
>   * pointer, if it is present (initialized to %NULL otherwise).
>   */
> -struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool,
> u64 addr)
> +struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool,
> u64 addr,
> +				   u32 options)
>  {
>  	struct xdp_desc_ctx ret;
> 
>  	addr = __xp_raw_get_addr(pool, addr);
> 
>  	ret.dma = __xp_raw_get_dma(pool, addr);
> -	ret.meta = __xsk_buff_get_metadata(pool,
> __xp_raw_get_data(pool, addr));
> +	ret.meta = __xsk_buff_get_metadata(pool,
> __xp_raw_get_data(pool, addr),
> +					   options);
> 
>  	return ret;
>  }
> --
> 2.53.0-Meta

Reviewed-by: Aleksandr Loktionov <[email protected]>