ixgbevf: implement CONFIG_NET_RX_BUSY_POLL

This patch enables CONFIG_NET_RX_BUSY_POLL support in the VF code. This enables
sockets which have enabled the SO_BUSY_POLL socket option to use the
ndo_busy_poll_recv operation which could result in lower latency, at the cost
of higher CPU utilization, and increased power usage. This support is similar
to how the ixgbe driver works.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 109 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
index d7837dcc9897..85c7560e237b 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf.h
@@ -38,6 +38,10 @@
 
 #include "vf.h"
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
+#include <net/busy_poll.h>
+#endif
+
 /* wrapper around a pointer to a socket buffer,
  * so a DMA handle can be stored along with the buffer */
 struct ixgbevf_tx_buffer {
@@ -145,7 +149,112 @@ struct ixgbevf_q_vector {
 	struct napi_struct napi;
 	struct ixgbevf_ring_container rx, tx;
 	char name[IFNAMSIZ + 9];
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	unsigned int state;
+#define IXGBEVF_QV_STATE_IDLE		0
+#define IXGBEVF_QV_STATE_NAPI		1    /* NAPI owns this QV */
+#define IXGBEVF_QV_STATE_POLL		2    /* poll owns this QV */
+#define IXGBEVF_QV_STATE_DISABLED	4    /* QV is disabled */
+#define IXGBEVF_QV_OWNED (IXGBEVF_QV_STATE_NAPI | IXGBEVF_QV_STATE_POLL)
+#define IXGBEVF_QV_LOCKED (IXGBEVF_QV_OWNED | IXGBEVF_QV_STATE_DISABLED)
+#define IXGBEVF_QV_STATE_NAPI_YIELD	8    /* NAPI yielded this QV */
+#define IXGBEVF_QV_STATE_POLL_YIELD	16   /* poll yielded this QV */
+#define IXGBEVF_QV_YIELD (IXGBEVF_QV_STATE_NAPI_YIELD | IXGBEVF_QV_STATE_POLL_YIELD)
+#define IXGBEVF_QV_USER_PEND (IXGBEVF_QV_STATE_POLL | IXGBEVF_QV_STATE_POLL_YIELD)
+	spinlock_t lock;
+#endif /* CONFIG_NET_RX_BUSY_POLL */
 };
+#ifdef CONFIG_NET_RX_BUSY_POLL
+static inline void ixgbevf_qv_init_lock(struct ixgbevf_q_vector *q_vector)
+{
+
+	spin_lock_init(&q_vector->lock);
+	q_vector->state = IXGBEVF_QV_STATE_IDLE;
+}
+
+/* called from the device poll routine to get ownership of a q_vector */
+static inline bool ixgbevf_qv_lock_napi(struct ixgbevf_q_vector *q_vector)
+{
+	int rc = true;
+	spin_lock_bh(&q_vector->lock);
+	if (q_vector->state & IXGBEVF_QV_LOCKED) {
+		WARN_ON(q_vector->state & IXGBEVF_QV_STATE_NAPI);
+		q_vector->state |= IXGBEVF_QV_STATE_NAPI_YIELD;
+		rc = false;
+	} else {
+		/* we don't care if someone yielded */
+		q_vector->state = IXGBEVF_QV_STATE_NAPI;
+	}
+	spin_unlock_bh(&q_vector->lock);
+	return rc;
+}
+
+/* returns true is someone tried to get the qv while napi had it */
+static inline bool ixgbevf_qv_unlock_napi(struct ixgbevf_q_vector *q_vector)
+{
+	int rc = false;
+	spin_lock_bh(&q_vector->lock);
+	WARN_ON(q_vector->state & (IXGBEVF_QV_STATE_POLL |
+				   IXGBEVF_QV_STATE_NAPI_YIELD));
+
+	if (q_vector->state & IXGBEVF_QV_STATE_POLL_YIELD)
+		rc = true;
+	/* reset state to idle, unless QV is disabled */
+	q_vector->state &= IXGBEVF_QV_STATE_DISABLED;
+	spin_unlock_bh(&q_vector->lock);
+	return rc;
+}
+
+/* called from ixgbevf_low_latency_poll() */
+static inline bool ixgbevf_qv_lock_poll(struct ixgbevf_q_vector *q_vector)
+{
+	int rc = true;
+	spin_lock_bh(&q_vector->lock);
+	if ((q_vector->state & IXGBEVF_QV_LOCKED)) {
+		q_vector->state |= IXGBEVF_QV_STATE_POLL_YIELD;
+		rc = false;
+	} else {
+		/* preserve yield marks */
+		q_vector->state |= IXGBEVF_QV_STATE_POLL;
+	}
+	spin_unlock_bh(&q_vector->lock);
+	return rc;
+}
+
+/* returns true if someone tried to get the qv while it was locked */
+static inline bool ixgbevf_qv_unlock_poll(struct ixgbevf_q_vector *q_vector)
+{
+	int rc = false;
+	spin_lock_bh(&q_vector->lock);
+	WARN_ON(q_vector->state & (IXGBEVF_QV_STATE_NAPI));
+
+	if (q_vector->state & IXGBEVF_QV_STATE_POLL_YIELD)
+		rc = true;
+	/* reset state to idle, unless QV is disabled */
+	q_vector->state &= IXGBEVF_QV_STATE_DISABLED;
+	spin_unlock_bh(&q_vector->lock);
+	return rc;
+}
+
+/* true if a socket is polling, even if it did not get the lock */
+static inline bool ixgbevf_qv_busy_polling(struct ixgbevf_q_vector *q_vector)
+{
+	WARN_ON(!(q_vector->state & IXGBEVF_QV_OWNED));
+	return q_vector->state & IXGBEVF_QV_USER_PEND;
+}
+
+/* false if QV is currently owned */
+static inline bool ixgbevf_qv_disable(struct ixgbevf_q_vector *q_vector)
+{
+	int rc = true;
+	spin_lock_bh(&q_vector->lock);
+	if (q_vector->state & IXGBEVF_QV_OWNED)
+		rc = false;
+	spin_unlock_bh(&q_vector->lock);
+	return rc;
+}
+
+#endif /* CONFIG_NET_RX_BUSY_POLL */
 
 /*
  * microsecond values for various ITR rates shifted by 2 to fit itr register