Re: [PATCH v5 net-next 11/13] net: enetc: optimize the allocation of tx_bdr

Vladimir Oltean
2024-10-25T09:51:42Z

On Thu, Oct 24, 2024 at 02:53:26PM +0800, Wei Fang wrote:
> From: Clark Wang <xiaoning.wang@nxp.com>
>
> There is a situation where num_tx_rings cannot be divided by bdr_int_num.
> For example, num_tx_rings is 8 and bdr_int_num is 3. According to the
> previous logic, this results in two tx_bdr corresponding memories not
> being allocated, so when sending packets to tx ring 6 or 7, wild pointers
> will be accessed. Of course, this issue doesn't exist on LS1028A, because
> its num_tx_rings is 8, and bdr_int_num is either 1 or 2. However, there
> is a risk for the upcoming i.MX95. Therefore, it is necessary to ensure
> that each tx_bdr can be allocated to the corresponding memory.
>
> Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
> Signed-off-by: Wei Fang <wei.fang@nxp.com>
> Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
> v5: no changes
> ---
> drivers/net/ethernet/freescale/enetc/enetc.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index bd725561b8a2..bccbeb1f355c 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -3049,10 +3049,10 @@ static void enetc_int_vector_destroy(struct enetc_ndev_priv *priv, int i)
> int enetc_alloc_msix(struct enetc_ndev_priv *priv)
> {
> struct pci_dev *pdev = priv->si->pdev;
> + int v_tx_rings, v_remainder;
> int num_stack_tx_queues;
> int first_xdp_tx_ring;
> int i, n, err, nvec;
> - int v_tx_rings;
>
> nvec = ENETC_BDR_INT_BASE_IDX + priv->bdr_int_num;
> /* allocate MSIX for both messaging and Rx/Tx interrupts */
> @@ -3066,9 +3066,12 @@ int enetc_alloc_msix(struct enetc_ndev_priv *priv)
>
> /* # of tx rings per int vector */
> v_tx_rings = priv->num_tx_rings / priv->bdr_int_num;
> + v_remainder = priv->num_tx_rings % priv->bdr_int_num;
>
> for (i = 0; i < priv->bdr_int_num; i++) {
> - err = enetc_int_vector_init(priv, i, v_tx_rings);
> + int num_tx_rings = i < v_remainder ? v_tx_rings + 1 : v_tx_rings;

It took me a moment to understand the mechanism through which this
works, even though I read the intention in the commit message.

Do you think this additional comment would help?

/* Distribute the remaining TX rings to the first
* v_tx_rings interrupt vectors
*/

> +
> + err = enetc_int_vector_init(priv, i, num_tx_rings);
> if (err)
> goto fail;
> }
> --
> 2.34.1
>