Re: [PATCH v5] net/mlx5: prepend implicit items in sync flow creation path

[Raslan Darawsheh <rasland@nvidia.com>]

Hi,


On 27/05/2026 1:35 PM, Maxime Peim wrote:
> In eSwitch mode, the async (template) flow creation path automatically
> prepends implicit match items to scope flow rules to the correct
> representor port:
>    - Ingress: REPRESENTED_PORT item matching dev->data->port_id
>    - Egress: REG_C_0 TAG item matching the port's tx tag value
> 
> The sync path (flow_hw_list_create) was missing this logic, causing all
> flow rules created via the non-template API to match traffic from all
> ports rather than being scoped to the specific representor.
> 
> Add the same implicit item prepending to flow_hw_list_create, right
> after pattern validation and before any branching (sample/RSS/single/
> prefix), mirroring the behavior of flow_hw_pattern_template_create
> and flow_hw_get_rule_items. The ingress case prepends
> REPRESENTED_PORT with the current port_id; the egress case prepends
> MLX5_RTE_FLOW_ITEM_TYPE_TAG with REG_C_0 value/mask (skipped when
> user provides an explicit SQ item).
> 
> Also fix a pre-existing bug where 'return split' on metadata split
> failure returned a negative int cast to uintptr_t, which callers
> would treat as a valid flow handle instead of an error.
> 
> Fixes: e38776c36c8a ("net/mlx5: introduce HWS for non-template flow API")
> Fixes: 821a6a5cc495 ("net/mlx5: add metadata split for compatibility")
> Signed-off-by: Maxime Peim <maxime.peim@gmail.com>
> ---
> v3:
>    - Factor the implicit-item prepend logic out of
>      flow_hw_pattern_template_create() into a new helper
>      flow_hw_adjust_pattern() and reuse it from flow_hw_list_create(),
>      instead of duplicating the prepend logic inline in the sync path.
>    - Zero-initialize item_flags in both callers. The validator is
>      read-modify-write on item_flags (reads MLX5_FLOW_LAYER_TUNNEL on
>      the first iteration), so leaving it uninitialized was UB.
>    - Call __flow_hw_pattern_validate() with nt_flow=true from the sync
>      path (was effectively nt_flow=false via the wrapper), restoring the
>      previous behavior that skips GENEVE_OPT TLV parser validation on
>      the non-template path.
>    - Document flow_hw_adjust_pattern(): the dual role of the nt_flow
>      parameter (template spec-left-zero vs. sync spec-filled + validator
>      flag), the three-way return, and the caller's ownership of
>      *copied_items across every exit path.
>    - Clarify the "omitting implicit REG_C_0 match" debug log now that
>      the helper runs on both the template and sync paths.
>    - Add Fixes: tags for the two original commits.
> 
> v4:
>    - Fix items in case splitted metadata are not needed.
> 
> v5:
>    - Make flow_hw_prepend_item() return a self-contained array. The
>      helper used to shallow-copy the prepended item, leaving its
>      .spec/.mask pointing at flow_hw_adjust_pattern()'s stack locals
>      (port_spec, tag_v, tag_m); once that frame returned, the
>      consumers in flow_hw_list_create() (sample / RSS / single create)
>      and the post-extraction template path dereferenced dangling
>      pointers. The prepended item is now deep-copied via
>      rte_flow_conv(RTE_FLOW_CONV_OP_ITEM, ...) into the tail of the
>      same mlx5_malloc() block, so the lifetime of every byte the
>      consumer can reach equals the lifetime of the returned array.
>      items[] continue to be shallow-copied (their spec/mask blobs are
>      application-owned and outlive the call). One alloc, one free; no
>      call-site or signature changes.
>    - Fix the &item_flags / &orig_item_nb argument order at both
>      flow_hw_adjust_pattern() call sites (introduced in v3 by the
>      helper extraction): the prior order silently stored the item
>      count into it->item_flags / the layer-flag arguments forwarded
>      into mlx5_nta_sample_flow_list_create / mlx5_flow_nta_handle_rss /
>      mlx5_flow_hw_create_flow, and stored the OR-accumulated layer
>      flags into it->orig_item_nb / per-rule item-count uses.
> 
>   drivers/net/mlx5/mlx5_flow_hw.c | 262 +++++++++++++++++++++++---------
>   1 file changed, 194 insertions(+), 68 deletions(-)
> 
--
Patch applied to next-net-mlx,

Kindest regards
Raslan Darawsheh