RE: [PATCH] ethernet: intel: fix building with large NR_CPUS

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Arnd Bergmann <arnd@xxxxxxxxxx>
> Sent: Friday, June 20, 2025 1:11 PM
> To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel,
> Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>; Andrew Lunn
> <andrew+netdev@xxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric
> Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>; Loktionov, Aleksandr
> <aleksandr.loktionov@xxxxxxxxx>; Simon Horman <horms@xxxxxxxxxx>;
> intel-wired-lan@xxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH] ethernet: intel: fix building with large NR_CPUS
> 
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> With large values of CONFIG_NR_CPUS, three Intel ethernet drivers fail
> to compile like:
> 
> In function ‘i40e_free_q_vector’,
>     inlined from ‘i40e_vsi_alloc_q_vectors’ at
> drivers/net/ethernet/intel/i40e/i40e_main.c:12112:3:
>   571 |         _compiletime_assert(condition, msg,
> __compiletime_assert_, __COUNTER__)
> include/linux/rcupdate.h:1084:17: note: in expansion of macro
> ‘BUILD_BUG_ON’
>  1084 |                 BUILD_BUG_ON(offsetof(typeof(*(ptr)), rhf) >=
> 4096);    \
> drivers/net/ethernet/intel/i40e/i40e_main.c:5113:9: note: in expansion
> of macro ‘kfree_rcu’
>  5113 |         kfree_rcu(q_vector, rcu);
>       |         ^~~~~~~~~
> 
> The problem is that the 'rcu' member in 'q_vector' is too far from the
> start of the structure. Move this member before the CPU mask instead,
> in all three drivers.
> 
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>
> ---
>  drivers/net/ethernet/intel/fm10k/fm10k.h | 2 +-
>  drivers/net/ethernet/intel/i40e/i40e.h   | 2 +-
>  drivers/net/ethernet/intel/ixgbe/ixgbe.h | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/fm10k/fm10k.h
> b/drivers/net/ethernet/intel/fm10k/fm10k.h
> index 6119a4108838..757a6fd81b7b 100644
> --- a/drivers/net/ethernet/intel/fm10k/fm10k.h
> +++ b/drivers/net/ethernet/intel/fm10k/fm10k.h
> @@ -187,6 +187,7 @@ struct fm10k_q_vector {
>  	u32 __iomem *itr;	/* pointer to ITR register for this vector
> */
>  	u16 v_idx;		/* index of q_vector within interface array
> */
>  	struct fm10k_ring_container rx, tx;
> +	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
> 
>  	struct napi_struct napi;
>  	cpumask_t affinity_mask;
> @@ -195,7 +196,6 @@ struct fm10k_q_vector {  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *dbg_q_vector;
>  #endif /* CONFIG_DEBUG_FS */
> -	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
> 
>  	/* for dynamic allocation of rings associated with this
> q_vector */
>  	struct fm10k_ring ring[] ____cacheline_internodealigned_in_smp;
> diff --git a/drivers/net/ethernet/intel/i40e/i40e.h
> b/drivers/net/ethernet/intel/i40e/i40e.h
> index 54d5fdc303ca..91aa88366c05 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e.h
> +++ b/drivers/net/ethernet/intel/i40e/i40e.h
> @@ -944,6 +944,7 @@ struct i40e_q_vector {
> 
>  	u16 v_idx;		/* index in the vsi->q_vector array. */
>  	u16 reg_idx;		/* register index of the interrupt */
> +	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
> 
>  	struct napi_struct napi;
> 
> @@ -956,7 +957,6 @@ struct i40e_q_vector {
>  	cpumask_t affinity_mask;
>  	struct irq_affinity_notify affinity_notify;
> 
> -	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
>  	char name[I40E_INT_NAME_STR_LEN];
>  	bool arm_wb_state;
>  	bool in_busy_poll;
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> index c6772cd2d802..c6cfab0ff9d3 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> @@ -505,11 +505,11 @@ struct ixgbe_q_vector {
>  				 * represents the vector for this ring */
>  	u16 itr;		/* Interrupt throttle rate written to EITR
> */
>  	struct ixgbe_ring_container rx, tx;
> +	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
> 
>  	struct napi_struct napi;
>  	cpumask_t affinity_mask;
>  	int numa_node;
> -	struct rcu_head rcu;	/* to avoid race with update stats on free
> */
>  	char name[IFNAMSIZ + 9];
> 
>  	/* for dynamic allocation of rings associated with this
> q_vector */
> --
> 2.39.5