sfc: fallback for lack of xdp tx queues

If there are not enough resources to allocate one TX queue per core for
XDP TX it was completely disabled.

This patch implements a fallback solution for sharing the available
queues using __netif_tx_lock for synchronization. In the normal case that
there is one TX queue per CPU, no locking is done, as it was before.

With this fallback solution, XDP TX will work in much more cases that
were failing, specially in machines with many CPUs. It's hard for XDP
users to know what features are supported across different NICs and
configurations, so they will benefit on having wider support.

Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 9b4b25704271..e731c766f709 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -782,6 +782,12 @@ struct efx_async_filter_insertion {
 #define EFX_RPS_MAX_IN_FLIGHT	8
 #endif /* CONFIG_RFS_ACCEL */
 
+enum efx_xdp_tx_queues_mode {
+	EFX_XDP_TX_QUEUES_DEDICATED,	/* one queue per core, locking not needed */
+	EFX_XDP_TX_QUEUES_SHARED,	/* each queue used by more than 1 core */
+	EFX_XDP_TX_QUEUES_DISABLED	/* xdp tx not available */
+};
+
 /**
  * struct efx_nic - an Efx NIC
  * @name: Device name (net device name or bus id before net device registered)
@@ -820,6 +826,7 @@ struct efx_async_filter_insertion {
  *	should be allocated for this NIC
  * @xdp_tx_queue_count: Number of entries in %xdp_tx_queues.
  * @xdp_tx_queues: Array of pointers to tx queues used for XDP transmit.
+ * @xdp_txq_queues_mode: XDP TX queues sharing strategy.
  * @rxq_entries: Size of receive queues requested by user.
  * @txq_entries: Size of transmit queues requested by user.
  * @txq_stop_thresh: TX queue fill level at or above which we stop it.
@@ -979,6 +986,7 @@ struct efx_nic {
 
 	unsigned int xdp_tx_queue_count;
 	struct efx_tx_queue **xdp_tx_queues;
+	enum efx_xdp_tx_queues_mode xdp_txq_queues_mode;
 
 	unsigned rxq_entries;
 	unsigned txq_entries;