sfc: Allow driver to cope with a lower number of VIs than it needs for RSS

Previously, the driver would refuse to load if it couldn't secure
enough VIs from the MC to fulfill its RSS requirements.
This was causing probe to fail on later functions in
configurations where we'd run out of VIs, such as having many
VFs.

This change allows the driver to load with fewer VIs, down to a
minimum of 2. A warning will be printed saying that RSS
requirements were not met, possibly affecting performance.

efx->max_tx_channels needs to be set to avoid going down the
failure path in efx_probe_nic() immediately in the loop after the
probe() NIC-type function.
Also, Set rc=ENOSPC when bombing out of efx_probe_nic due to lack
of VIs.

Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 18 deletions

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 03bc03b67f08..974637d3ae25 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -115,9 +115,9 @@ static struct workqueue_struct *reset_workqueue;
  *
  * This is only used in MSI-X interrupt mode
  */
-static bool separate_tx_channels;
-module_param(separate_tx_channels, bool, 0444);
-MODULE_PARM_DESC(separate_tx_channels,
+bool efx_separate_tx_channels;
+module_param(efx_separate_tx_channels, bool, 0444);
+MODULE_PARM_DESC(efx_separate_tx_channels,
 		 "Use separate channels for TX and RX");
 
 /* This is the weight assigned to each of the (per-channel) virtual
@@ -1391,7 +1391,7 @@ static int efx_probe_interrupts(struct efx_nic *efx)
 		unsigned int n_channels;
 
 		n_channels = efx_wanted_parallelism(efx);
-		if (separate_tx_channels)
+		if (efx_separate_tx_channels)
 			n_channels *= 2;
 		n_channels += extra_channels;
 		n_channels = min(n_channels, efx->max_channels);
@@ -1418,13 +1418,16 @@ static int efx_probe_interrupts(struct efx_nic *efx)
 			efx->n_channels = n_channels;
 			if (n_channels > extra_channels)
 				n_channels -= extra_channels;
-			if (separate_tx_channels) {
-				efx->n_tx_channels = max(n_channels / 2, 1U);
+			if (efx_separate_tx_channels) {
+				efx->n_tx_channels = min(max(n_channels / 2,
+							     1U),
+							 efx->max_tx_channels);
 				efx->n_rx_channels = max(n_channels -
 							 efx->n_tx_channels,
 							 1U);
 			} else {
-				efx->n_tx_channels = n_channels;
+				efx->n_tx_channels = min(n_channels,
+							 efx->max_tx_channels);
 				efx->n_rx_channels = n_channels;
 			}
 			for (i = 0; i < efx->n_channels; i++)
@@ -1450,7 +1453,7 @@ static int efx_probe_interrupts(struct efx_nic *efx)
 
 	/* Assume legacy interrupts */
 	if (efx->interrupt_mode == EFX_INT_MODE_LEGACY) {
-		efx->n_channels = 1 + (separate_tx_channels ? 1 : 0);
+		efx->n_channels = 1 + (efx_separate_tx_channels ? 1 : 0);
 		efx->n_rx_channels = 1;
 		efx->n_tx_channels = 1;
 		efx->legacy_irq = efx->pci_dev->irq;
@@ -1624,7 +1627,8 @@ static void efx_set_channels(struct efx_nic *efx)
 	struct efx_tx_queue *tx_queue;
 
 	efx->tx_channel_offset =
-		separate_tx_channels ? efx->n_channels - efx->n_tx_channels : 0;
+		efx_separate_tx_channels ?
+		efx->n_channels - efx->n_tx_channels : 0;
 
 	/* We need to mark which channels really have RX and TX
 	 * queues, and adjust the TX queue numbers if we have separate
@@ -1653,17 +1657,34 @@ static int efx_probe_nic(struct efx_nic *efx)
 	if (rc)
 		return rc;
 
-	/* Determine the number of channels and queues by trying to hook
-	 * in MSI-X interrupts. */
-	rc = efx_probe_interrupts(efx);
-	if (rc)
-		goto fail1;
+	do {
+		if (!efx->max_channels || !efx->max_tx_channels) {
+			netif_err(efx, drv, efx->net_dev,
+				  "Insufficient resources to allocate"
+				  " any channels\n");
+			rc = -ENOSPC;
+			goto fail1;
+		}
 
-	efx_set_channels(efx);
+		/* Determine the number of channels and queues by trying
+		 * to hook in MSI-X interrupts.
+		 */
+		rc = efx_probe_interrupts(efx);
+		if (rc)
+			goto fail1;
 
-	rc = efx->type->dimension_resources(efx);
-	if (rc)
-		goto fail2;
+		efx_set_channels(efx);
+
+		/* dimension_resources can fail with EAGAIN */
+		rc = efx->type->dimension_resources(efx);
+		if (rc != 0 && rc != -EAGAIN)
+			goto fail2;
+
+		if (rc == -EAGAIN)
+			/* try again with new max_channels */
+			efx_remove_interrupts(efx);
+
+	} while (rc == -EAGAIN);
 
 	if (efx->n_channels > 1)
 		netdev_rss_key_fill(&efx->rx_hash_key,