netdev - [PATCH net-next 09/15] net/mlx5e: XDP, Consider large muti-buffer packets in Striding RQ params calculations

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Message-ID: <20230417121903.46218-10-tariqt@nvidia.com>
Date:   Mon, 17 Apr 2023 15:18:57 +0300
From:   Tariq Toukan <tariqt@...dia.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Hoiland-Jorgensen <toke@...hat.com>,
        <netdev@...r.kernel.org>, Saeed Mahameed <saeedm@...dia.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Gal Pressman <gal@...dia.com>,
        Henning Fehrmann <henning.fehrmann@....mpg.de>,
        "Oliver Behnke" <oliver.behnke@....mpg.de>,
        Tariq Toukan <tariqt@...dia.com>
Subject: [PATCH net-next 09/15] net/mlx5e: XDP, Consider large muti-buffer packets in Striding RQ params calculations

Function mlx5e_rx_get_linear_stride_sz() returns PAGE_SIZE immediately
in case an XDP program is attached. The more accurate formula is
ALIGN(sz, PAGE_SIZE), to prevent two packets from residing on the same
page.

The assumption behind the current code is that sz <= PAGE_SIZE holds for
all cases with XDP program set.

This is true because it is being called from:
- 3 times from Striding RQ flows, in which XDP is not supported for such
  large packets.
- 1 time from Legacy RQ flow, under the condition
  mlx5e_rx_is_linear_skb().

No functional change here, just removing the implied assumption in
preparation for supporting XDP multi-buffer in Striding RQ.

Reviewed-by: Saeed Mahameed <saeedm@...dia.com>
Signed-off-by: Tariq Toukan <tariqt@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/params.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 31f3c6e51d9e..196862e67af3 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -253,17 +253,20 @@ static u32 mlx5e_rx_get_linear_stride_sz(struct mlx5_core_dev *mdev,
 					 struct mlx5e_xsk_param *xsk,
 					 bool mpwqe)
 {
+	u32 sz;
+
 	/* XSK frames are mapped as individual pages, because frames may come in
 	 * an arbitrary order from random locations in the UMEM.
 	 */
 	if (xsk)
 		return mpwqe ? 1 << mlx5e_mpwrq_page_shift(mdev, xsk) : PAGE_SIZE;
 
-	/* XDP in mlx5e doesn't support multiple packets per page. */
-	if (params->xdp_prog)
-		return PAGE_SIZE;
+	sz = roundup_pow_of_two(mlx5e_rx_get_linear_sz_skb(params, false));
 
-	return roundup_pow_of_two(mlx5e_rx_get_linear_sz_skb(params, false));
+	/* XDP in mlx5e doesn't support multiple packets per page.
+	 * Do not assume sz <= PAGE_SIZE if params->xdp_prog is set.
+	 */
+	return params->xdp_prog && sz < PAGE_SIZE ? PAGE_SIZE : sz;
 }
 
 static u8 mlx5e_mpwqe_log_pkts_per_wqe(struct mlx5_core_dev *mdev,
-- 
2.34.1