Commit 555a05d8 authored by Vladimir Oltean's avatar Vladimir Oltean Committed by Jakub Kicinski
Browse files

net: dpaa: avoid on-stack arrays of NR_CPUS elements 

The dpaa-eth driver is written for PowerPC and Arm SoCs which have 1-24
CPUs. It depends on CONFIG_NR_CPUS having a reasonably small value in
Kconfig. Otherwise, there are 2 functions which allocate on-stack arrays
of NR_CPUS elements, and these can quickly explode in size, leading to
warnings such as:

  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:3280:12: warning:
  stack frame size (16664) exceeds limit (2048) in 'dpaa_eth_probe' [-Wframe-larger-than]

The problem is twofold:
- Reducing the array size to the boot-time num_possible_cpus() (rather
  than the compile-time NR_CPUS) creates a variable-length array,
  which should be avoided in the Linux kernel.
- Using NR_CPUS as an array size makes the driver blow up in stack
  consumption with generic, as opposed to hand-crafted, .config files.

A simple solution is to use dynamic allocation for num_possible_cpus()
elements (aka a small number determined at runtime).

Link: https://lore.kernel.org/all/202406261920.l5pzM1rj-lkp@intel.com/


Signed-off-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: default avatarBreno Leitao <leitao@debian.org>
Acked-by: default avatarMadalin Bucur <madalin.bucur@oss.nxp.com>
Link: https://patch.msgid.link/20240713225336.1746343-2-vladimir.oltean@nxp.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 62fdd170

drivers/net/ethernet/freescale/dpaa/dpaa_eth.c

+15 −5
Original line number Diff line number Diff line
@@ -931,14 +931,18 @@ static inline void dpaa_setup_egress(const struct dpaa_priv *priv, 
	}

}



static void dpaa_fq_setup(struct dpaa_priv *priv,

static int dpaa_fq_setup(struct dpaa_priv *priv,

			 const struct dpaa_fq_cbs *fq_cbs,

			 struct fman_port *tx_port)

{

	int egress_cnt = 0, conf_cnt = 0, num_portals = 0, portal_cnt = 0, cpu;

	const cpumask_t *affine_cpus = qman_affine_cpus();

	u16 channels[NR_CPUS];

	struct dpaa_fq *fq;

	u16 *channels;



	channels = kcalloc(num_possible_cpus(), sizeof(u16), GFP_KERNEL);

	if (!channels)

		return -ENOMEM;



	for_each_cpu_and(cpu, affine_cpus, cpu_online_mask)

		channels[num_portals++] = qman_affine_channel(cpu);
@@ -997,6 +1001,10 @@ static void dpaa_fq_setup(struct dpaa_priv *priv, 
				break;

		}

	}



	kfree(channels);



	return 0;

}



static inline int dpaa_tx_fq_to_id(const struct dpaa_priv *priv,
@@ -3416,7 +3424,9 @@ static int dpaa_eth_probe(struct platform_device *pdev) 
	 */

	dpaa_eth_add_channel(priv->channel, &pdev->dev);



	dpaa_fq_setup(priv, &dpaa_fq_cbs, priv->mac_dev->port[TX]);

	err = dpaa_fq_setup(priv, &dpaa_fq_cbs, priv->mac_dev->port[TX]);

	if (err)

		goto free_dpaa_bps;



	/* Create a congestion group for this netdev, with

	 * dynamically-allocated CGR ID.

drivers/net/ethernet/freescale/dpaa/dpaa_ethtool.c

+9 −1
Original line number Diff line number Diff line
@@ -457,12 +457,16 @@ static int dpaa_set_coalesce(struct net_device *dev, 
			     struct netlink_ext_ack *extack)

{

	const cpumask_t *cpus = qman_affine_cpus();

	bool needs_revert[NR_CPUS] = {false};

	struct qman_portal *portal;

	u32 period, prev_period;

	u8 thresh, prev_thresh;

	bool *needs_revert;

	int cpu, res;



	needs_revert = kcalloc(num_possible_cpus(), sizeof(bool), GFP_KERNEL);

	if (!needs_revert)

		return -ENOMEM;



	period = c->rx_coalesce_usecs;

	thresh = c->rx_max_coalesced_frames;
@@ -485,6 +489,8 @@ static int dpaa_set_coalesce(struct net_device *dev, 
		needs_revert[cpu] = true;

	}



	kfree(needs_revert);



	return 0;



revert_values:
@@ -498,6 +504,8 @@ static int dpaa_set_coalesce(struct net_device *dev, 
		qman_dqrr_set_ithresh(portal, prev_thresh);

	}



	kfree(needs_revert);



	return res;

}