Re: [PATCH net-next 05/12] net/mlx5: fs, add mlx5_fs_pool API

[Kees Cook <kees@kernel.org>]

On Sun, Dec 15, 2024 at 03:39:11PM +0200, Moshe Shemesh wrote:
> 
> 
> On 12/12/2024 7:23 PM, Simon Horman wrote:
> > External email: Use caution opening links or attachments
> > 
> > 
> > On Wed, Dec 11, 2024 at 03:42:16PM +0200, Tariq Toukan wrote:
> > > From: Moshe Shemesh <moshe@nvidia.com>
> > > 
> > > Refactor fc_pool API to create generic fs_pool API, as HW steering has
> > > more flow steering elements which can take advantage of the same pool of
> > > bulks API. Change fs_counters code to use the fs_pool API.
> > > 
> > > Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
> > > Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
> > > Reviewed-by: Mark Bloch <mbloch@nvidia.com>
> > > Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
> > 
> > ...
> > 
> > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> > 
> > ...
> > 
> > > @@ -447,11 +437,9 @@ void mlx5_fc_update_sampling_interval(struct mlx5_core_dev *dev,
> > >   /* Flow counter bluks */
> > > 
> > >   struct mlx5_fc_bulk {
> > > -     struct list_head pool_list;
> > > +     struct mlx5_fs_bulk fs_bulk;
> > >        u32 base_id;
> > > -     int bulk_len;
> > > -     unsigned long *bitmask;
> > > -     struct mlx5_fc fcs[] __counted_by(bulk_len);
> > > +     struct mlx5_fc fcs[] __counted_by(fs_bulk.bulk_len);
> > >   };
> > 
> > Unfortunately it seems that clang-19 doesn't know how to handle
> > __counted_by() when used like this:
> > 
> > drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c:442:36: error: 'counted_by' argument must be a simple declaration reference
> >    442 |         struct mlx5_fc fcs[] __counted_by(fs_bulk.bulk_len);
> 
> Thanks Simon, from code perspective, bulk_len should be now in the inner
> struct fs_bulk.
> 
> Keen Cook, is that going to be supported in the future? for now I will just
> remove __counted_by() from this struct.

I am expecting this will be supported in the future, yes, but there isn't
an ETA for it yet. Neither GCC 15 nor Clang are currently supporting
sub-struct members -- the counted_by member needs to be at the same
"level" in the struct as the annotated flexible array.

Is it possible to move "base_id" above "fs_bulk" and move "fcs" into
the of end struct mlx5_fs_bulk?

-Kees

-- 
Kees Cook