[PATCH net v2 7/9] gve: disable NAPI when registering XSK pools in QPL mode

[Joshua Washington <joshwash@google.com>]

As a result of QPL modes not posting XSK buffers directly to the NIC,
they do not need to recreate queues or re-post DMA buffers.

However, traffic should still be quiesced because both the driver and
the XDP redirect stack must have the same knowledge about whether a
given packet is being processed with AF_XDP zero-copy enabled or not.
GVE in QPL mode does not current respect this, which could lead to a
race condition between packet processing and the XSK_BUFF_POOL memory
model registration.

Quiesce traffic by disabling the NAPI while the XSK_BUFF_POOL memory
model is being registered with the kernel.

Fixes: fd8e40321a12 ("gve: Add AF_XDP zero-copy support for GQI-QPL format")
Cc: stable@vger.kernel.org
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
---
v2:
- newly introduced
---
 drivers/net/ethernet/google/gve/gve_main.c | 41 ++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 49ae2b8c6a27..f2bd4011de23 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -1626,6 +1626,40 @@ static int gve_xdp_xmit(struct net_device *dev, int n,
 	return -EOPNOTSUPP;
 }
 
+static void gve_disable_xsk_napis(struct gve_priv *priv, u16 qid)
+{
+	struct napi_struct *napi_rx, *napi_tx;
+	u16 tx_qid;
+
+	napi_rx = &priv->ntfy_blocks[priv->rx[qid].ntfy_id].napi;
+	napi_disable_locked(napi_rx);
+
+	tx_qid = gve_xdp_tx_queue_id(priv, qid);
+	napi_tx = &priv->ntfy_blocks[priv->tx[tx_qid].ntfy_id].napi;
+	napi_disable_locked(napi_tx);
+}
+
+static void gve_enable_xsk_napis(struct gve_priv *priv, u16 qid)
+{
+	struct napi_struct *napi_rx, *napi_tx;
+	u16 tx_qid;
+
+	napi_rx = &priv->ntfy_blocks[priv->rx[qid].ntfy_id].napi;
+	napi_enable_locked(napi_rx);
+
+	tx_qid = gve_xdp_tx_queue_id(priv, qid);
+	napi_tx = &priv->ntfy_blocks[priv->tx[tx_qid].ntfy_id].napi;
+	napi_enable_locked(napi_tx);
+
+	if (gve_is_gqi(priv)) {
+		if (gve_rx_work_pending(&priv->rx[qid]))
+			napi_schedule(napi_rx);
+
+		if (gve_tx_clean_pending(priv, &priv->tx[tx_qid]))
+			napi_schedule(napi_tx);
+	}
+}
+
 static int gve_xsk_pool_enable(struct net_device *dev,
 			       struct xsk_buff_pool *pool,
 			       u16 qid)
@@ -1655,7 +1689,14 @@ static int gve_xsk_pool_enable(struct net_device *dev,
 		return 0;
 
 	if (gve_is_qpl(priv)) {
+		gve_disable_xsk_napis(priv, qid);
+
 		err = gve_reg_xsk_pool(priv, dev, pool, qid);
+		/* Make sure it is visible to the workers on datapath */
+		smp_mb();
+
+		gve_enable_xsk_napis(priv, qid);
+
 		if (err)
 			goto err_xsk_pool_dma_mapped;
 	} else {
-- 
2.55.0.1082.g2b9226bbc0-goog