diff mbox series

[net-next,02/15] net/mlx5e: Use fragments of the same size in non-linear legacy RQ with XDP

Message ID 20220318205248.33367-3-saeed@kernel.org (mailing list archive)
State Accepted
Commit 9cb9482ef10e7e524f73878cb20de138be7e1a1f
Delegated to: Netdev Maintainers
Headers show
Series [net-next,01/15] net/mlx5e: Prepare non-linear legacy RQ for XDP multi buffer support | expand

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netdev/fixes_present success Fixes tag not required for -next series
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netdev/cover_letter success Pull request is its own cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 11 maintainers not CCed: daniel@iogearbox.net ast@kernel.org songliubraving@fb.com andrii@kernel.org yhs@fb.com hawk@kernel.org john.fastabend@gmail.com pabeni@redhat.com kafai@fb.com kpsingh@kernel.org bpf@vger.kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
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netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns WARNING: line length of 82 exceeds 80 columns WARNING: line length of 85 exceeds 80 columns WARNING: line length of 92 exceeds 80 columns
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Commit Message

Saeed Mahameed March 18, 2022, 8:52 p.m. UTC 
From: Maxim Mikityanskiy <maximmi@nvidia.com>

XDP multi buffer implementation in the kernel assumes that all fragments
have the same size. bpf_xdp_frags_increase_tail uses this assumption to
get the size of the last fragment, and __xdp_build_skb_from_frame uses
it to calculate truesize as nr_frags * xdpf->frame_sz.

The current implementation of mlx5e uses fragments of different size in
non-linear legacy RQ. Specifically, the last fragment can be larger than
the others. It's an optimization for packets smaller than MTU.

This commit adapts mlx5e to the kernel limitations and makes it use
fragments of the same size, in order to add support for XDP multi
buffer. The change is applied only if XDP is active, otherwise the old
optimization still applies.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
---
 .../ethernet/mellanox/mlx5/core/en/params.c   | 28 +++++++++++++------
 1 file changed, 19 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 5c4711be6fae..822fbb9b80e7 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -398,8 +398,12 @@  void mlx5e_build_create_cq_param(struct mlx5e_create_cq_param *ccp, struct mlx5e
 	};
 }
 
-static int mlx5e_max_nonlinear_mtu(int first_frag_size, int frag_size)
+static int mlx5e_max_nonlinear_mtu(int first_frag_size, int frag_size, bool xdp)
 {
+	if (xdp)
+		/* XDP requires all fragments to be of the same size. */
+		return first_frag_size + (MLX5E_MAX_RX_FRAGS - 1) * frag_size;
+
 	/* Optimization for small packets: the last fragment is bigger than the others. */
 	return first_frag_size + (MLX5E_MAX_RX_FRAGS - 2) * frag_size + PAGE_SIZE;
 }
@@ -438,12 +442,14 @@  static int mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
 	headroom = mlx5e_get_linear_rq_headroom(params, xsk);
 	first_frag_size_max = SKB_WITH_OVERHEAD(frag_size_max - headroom);
 
-	max_mtu = mlx5e_max_nonlinear_mtu(first_frag_size_max, frag_size_max);
+	max_mtu = mlx5e_max_nonlinear_mtu(first_frag_size_max, frag_size_max,
+					  params->xdp_prog);
 	if (byte_count > max_mtu) {
 		frag_size_max = PAGE_SIZE;
 		first_frag_size_max = SKB_WITH_OVERHEAD(frag_size_max - headroom);
 
-		max_mtu = mlx5e_max_nonlinear_mtu(first_frag_size_max, frag_size_max);
+		max_mtu = mlx5e_max_nonlinear_mtu(first_frag_size_max, frag_size_max,
+						  params->xdp_prog);
 		if (byte_count > max_mtu) {
 			mlx5_core_err(mdev, "MTU %u is too big for non-linear legacy RQ (max %d)\n",
 				      params->sw_mtu, max_mtu);
@@ -463,14 +469,18 @@  static int mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
 		info->arr[i].frag_size = frag_size;
 		buf_size += frag_size;
 
-		if (i == 0) {
-			/* Ensure that headroom and tailroom are included. */
-			frag_size += headroom;
-			frag_size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+		if (params->xdp_prog) {
+			/* XDP multi buffer expects fragments of the same size. */
+			info->arr[i].frag_stride = frag_size_max;
+		} else {
+			if (i == 0) {
+				/* Ensure that headroom and tailroom are included. */
+				frag_size += headroom;
+				frag_size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+			}
+			info->arr[i].frag_stride = roundup_pow_of_two(frag_size);
 		}
 
-		info->arr[i].frag_stride = roundup_pow_of_two(frag_size);
-
 		i++;
 	}
 	info->num_frags = i;