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, 29 insertions, 10 deletions

diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c
index 9096b036d362..ff649ebef637 100644
--- a/drivers/net/ethernet/sfc/ef10.c
+++ b/drivers/net/ethernet/sfc/ef10.c
@@ -295,11 +295,11 @@ static int efx_ef10_probe(struct efx_nic *efx)
 	/* We can have one VI for each 8K region.  However, until we
 	 * use TX option descriptors we need two TX queues per channel.
 	 */
-	efx->max_channels =
-		min_t(unsigned int,
-		      EFX_MAX_CHANNELS,
-		      efx_ef10_mem_map_size(efx) /
-		      (EFX_VI_PAGE_SIZE * EFX_TXQ_TYPES));
+	efx->max_channels = min_t(unsigned int,
+				  EFX_MAX_CHANNELS,
+				  efx_ef10_mem_map_size(efx) /
+				  (EFX_VI_PAGE_SIZE * EFX_TXQ_TYPES));
+	efx->max_tx_channels = efx->max_channels;
 	if (WARN_ON(efx->max_channels == 0))
 		return -EIO;
 
@@ -824,11 +824,13 @@ static int efx_ef10_dimension_resources(struct efx_nic *efx)
 {
 	struct efx_ef10_nic_data *nic_data = efx->nic_data;
 	unsigned int uc_mem_map_size, wc_mem_map_size;
-	unsigned int min_vis, pio_write_vi_base, max_vis;
+	unsigned int min_vis = max(EFX_TXQ_TYPES,
+				   efx_separate_tx_channels ? 2 : 1);
+	unsigned int channel_vis, pio_write_vi_base, max_vis;
 	void __iomem *membase;
 	int rc;
 
-	min_vis = max(efx->n_channels, efx->n_tx_channels * EFX_TXQ_TYPES);
+	channel_vis = max(efx->n_channels, efx->n_tx_channels * EFX_TXQ_TYPES);
 
 #ifdef EFX_USE_PIO
 	/* Try to allocate PIO buffers if wanted and if the full
@@ -862,11 +864,11 @@ static int efx_ef10_dimension_resources(struct efx_nic *efx)
 	 * page size is >4K).  So we may allocate some extra VIs just
 	 * for writing PIO buffers through.
 	 *
-	 * The UC mapping contains (min_vis - 1) complete VIs and the
+	 * The UC mapping contains (channel_vis - 1) complete VIs and the
 	 * first half of the next VI.  Then the WC mapping begins with
 	 * the second half of this last VI.
 	 */
-	uc_mem_map_size = PAGE_ALIGN((min_vis - 1) * EFX_VI_PAGE_SIZE +
+	uc_mem_map_size = PAGE_ALIGN((channel_vis - 1) * EFX_VI_PAGE_SIZE +
 				     ER_DZ_TX_PIOBUF);
 	if (nic_data->n_piobufs) {
 		/* pio_write_vi_base rounds down to give the number of complete
@@ -881,7 +883,7 @@ static int efx_ef10_dimension_resources(struct efx_nic *efx)
 	} else {
 		pio_write_vi_base = 0;
 		wc_mem_map_size = 0;
-		max_vis = min_vis;
+		max_vis = channel_vis;
 	}
 
 	/* In case the last attached driver failed to free VIs, do it now */
@@ -893,6 +895,23 @@ static int efx_ef10_dimension_resources(struct efx_nic *efx)
 	if (rc != 0)
 		return rc;
 
+	if (nic_data->n_allocated_vis < channel_vis) {
+		netif_info(efx, drv, efx->net_dev,
+			   "Could not allocate enough VIs to satisfy RSS"
+			   " requirements. Performance may not be optimal.\n");
+		/* We didn't get the VIs to populate our channels.
+		 * We could keep what we got but then we'd have more
+		 * interrupts than we need.
+		 * Instead calculate new max_channels and restart
+		 */
+		efx->max_channels = nic_data->n_allocated_vis;
+		efx->max_tx_channels =
+			nic_data->n_allocated_vis / EFX_TXQ_TYPES;
+
+		efx_ef10_free_vis(efx);
+		return -EAGAIN;
+	}
+
 	/* If we didn't get enough VIs to map all the PIO buffers, free the
 	 * PIO buffers
 	 */