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i40e: Fix XDP redirect failure when queue count < CPU count #19

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i40e: Fix XDP redirect failure when queue count < CPU count #19

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11 changes: 11 additions & 0 deletions src/i40e_ethtool.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6508,6 +6508,17 @@ static int i40e_set_channels(struct net_device *dev,
if (count > i40e_max_channels(vsi))
return -EINVAL;

/* verify XDP program compatibility with requested channel count */
if (i40e_enabled_xdp_vsi(vsi) && count < num_online_cpus()) {
dev_warn(&pf->pdev->dev,
"XDP enabled: reducing channels (%u) below online CPUs (%u) may cause performance issues\n",
count, num_online_cpus());
dev_info(&pf->pdev->dev,
"Consider using channels >= %u for optimal XDP performance\n",
num_online_cpus());
/* Warning only - allow the configuration but inform user */
}

/* verify that the number of channels does not invalidate any current
* flow director rules
*/
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41 changes: 38 additions & 3 deletions src/i40e_txrx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4707,6 +4707,32 @@ netdev_tx_t i40e_lan_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
}

#ifdef HAVE_XDP_SUPPORT
/**
* i40e_xdp_queue_index - Get optimal queue index for XDP transmit
* @vsi: VSI structure
*
* Returns a valid queue index that maps current CPU to available queue pairs.
* Uses modulo operation to ensure index never exceeds num_queue_pairs.
**/
static inline unsigned int i40e_xdp_queue_index(struct i40e_vsi *vsi)
{
unsigned int cpu_id = smp_processor_id();
unsigned int queue_index = cpu_id % vsi->num_queue_pairs;

/* Warn once if CPU count exceeds queue count - suboptimal configuration */
if (unlikely(cpu_id >= vsi->num_queue_pairs)) {
static bool warned = false;
if (!warned) {
netdev_warn(vsi->netdev,
"XDP performance notice: CPU count (%u) exceeds queue count (%u). Consider using ethtool -L %s combined %u for optimal performance\n",
num_online_cpus(), vsi->num_queue_pairs, vsi->netdev->name, num_online_cpus());
warned = true;
}
}

return queue_index;
}

/**
* i40e_xdp_xmit - Implements ndo_xdp_xmit
* @dev: netdev
Expand All @@ -4728,8 +4754,8 @@ int i40e_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp)
#endif
{
struct i40e_netdev_priv *np = netdev_priv(dev);
unsigned int queue_index = smp_processor_id();
struct i40e_vsi *vsi = np->vsi;
unsigned int queue_index = i40e_xdp_queue_index(vsi);
struct i40e_pf *pf = vsi->back;
#ifdef HAVE_XDP_FRAME_STRUCT
struct i40e_ring *xdp_ring;
Expand All @@ -4741,8 +4767,17 @@ int i40e_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp)
if (test_bit(__I40E_VSI_DOWN, vsi->state))
return -ENETDOWN;

if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs ||
test_bit(__I40E_CONFIG_BUSY, pf->state))
if (!i40e_enabled_xdp_vsi(vsi))
return -ENXIO;

if (unlikely(queue_index >= vsi->num_queue_pairs)) {
/* This should never happen with fixed queue mapping, but keep as safety check */
netdev_err(dev, "BUG: XDP queue_index %u >= num_queue_pairs %u (CPU %u) - driver bug!\n",
queue_index, vsi->num_queue_pairs, smp_processor_id());
return -ENXIO;
}

if (test_bit(__I40E_CONFIG_BUSY, pf->state))
return -ENXIO;
#ifdef HAVE_XDP_FRAME_STRUCT
if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
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