[PATCH net v3 07/10] net: stmmac: account for failed live XDP reopening

[James Hilliard <james.hilliard1@gmail.com>]

The XDP-specific release/open pair bypasses the ordinary datapath
bookkeeping, and its caller ignores reopen errors. A failed allocation
therefore leaves the device marked running with NAPI disabled and rings
released. A later close disables NAPI again. An IRQ-request failure also
frees descriptors after starting DMA without first stopping it.

Detach and stop phylink while replacing the XDP datapath, update its
ownership state, and reattach only after successful reopening. Preserve
the existing PTP registration on success, but release it on failure so a
DOWN datapath has no residual PTP ownership. Drain transmitters and timer
producers after freeing IRQs which can restart TX queues, including on
the ordinary release path.

Keep the old program reference until the change has succeeded. On an
attach failure restore the old program and return the error, allowing the
core to release the proposed program. Program removal must still succeed
when the non-XDP datapath cannot restart: BPF link teardown cannot retain
the detached program. Leave the interface administratively up but detached
for an ordinary down/up recovery in either failure case.

Fixes: ac746c8520d9 ("net: stmmac: enhance XDP ZC driver level switching performance")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 47 +++++++++++++++--------
 drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c  | 31 +++++++++++----
 2 files changed, 54 insertions(+), 24 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index ce598b575763..467f471874cf 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4314,12 +4314,10 @@ static int stmmac_open(struct net_device *dev)
 	return ret;
 }
 
-/* Quiesce NAPI and transmit queues without releasing their resources. */
-static void stmmac_quiesce(struct stmmac_priv *priv)
+static void stmmac_stop_tx_queues(struct stmmac_priv *priv)
 {
 	u8 chan;
 
-	stmmac_disable_all_queues(priv);
 	netif_tx_disable(priv->dev);
 
 	/* A poll function can still arm a timer after napi_complete_done().
@@ -4332,6 +4330,13 @@ static void stmmac_quiesce(struct stmmac_priv *priv)
 		hrtimer_cancel(&priv->dma_conf->tx_queue[chan].txtimer);
 }
 
+/* Quiesce NAPI and transmit queues without releasing their resources. */
+static void stmmac_quiesce(struct stmmac_priv *priv)
+{
+	stmmac_disable_all_queues(priv);
+	stmmac_stop_tx_queues(priv);
+}
+
 static void __stmmac_release(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
@@ -4350,6 +4355,9 @@ static void __stmmac_release(struct net_device *dev)
 	/* Free the IRQ lines */
 	stmmac_free_irq(dev, REQ_IRQ_ERR_ALL, 0);
 
+	/* TX error IRQs can restart a queue after the first quiescence. */
+	stmmac_stop_tx_queues(priv);
+
 	/* Stop TX/RX DMA after draining IRQ handlers which can restart it. */
 	stmmac_stop_all_dma(priv);
 
@@ -7244,19 +7252,15 @@ void stmmac_enable_tx_queue(struct stmmac_priv *priv, u32 queue)
 void stmmac_xdp_release(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
-	u8 chan;
-
-	/* Ensure tx function is not running */
-	netif_tx_disable(dev);
 
-	/* Disable NAPI process */
-	stmmac_disable_all_queues(priv);
-
-	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)
-		hrtimer_cancel(&priv->dma_conf->tx_queue[chan].txtimer);
+	netif_device_detach(dev);
+	phylink_stop(priv->phylink);
+	stmmac_quiesce(priv);
+	priv->datapath = STMMAC_DATAPATH_DOWN;
 
 	/* Free the IRQ lines */
 	stmmac_free_irq(dev, REQ_IRQ_ERR_ALL, 0);
+	stmmac_stop_tx_queues(priv);
 
 	/* Stop TX/RX DMA channels */
 	stmmac_stop_all_dma(priv);
@@ -7271,7 +7275,13 @@ void stmmac_xdp_release(struct net_device *dev)
 	 * watchdogs during reset
 	 */
 	netif_trans_update(dev);
-	netif_carrier_off(dev);
+
+	if (stmmac_fpe_supported(priv))
+		ethtool_mmsv_stop(&priv->fpe_cfg.mmsv);
+
+	/* Keep PTP across the immediately following stmmac_xdp_open(). That
+	 * function releases it if reopening fails, before returning DOWN.
+	 */
 }
 
 int stmmac_xdp_open(struct net_device *dev)
@@ -7350,19 +7360,22 @@ int stmmac_xdp_open(struct net_device *dev)
 
 	/* Enable NAPI process*/
 	stmmac_enable_all_queues(priv);
-	netif_carrier_on(dev);
-	netif_tx_start_all_queues(dev);
 	stmmac_enable_all_dma_irq(priv);
+	priv->datapath = STMMAC_DATAPATH_RUNNING;
+	phylink_start(priv->phylink);
+	netif_device_attach(dev);
 
 	return 0;
 
 irq_error:
-	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)
-		hrtimer_cancel(&priv->dma_conf->tx_queue[chan].txtimer);
+	stmmac_stop_tx_queues(priv);
+	stmmac_stop_all_dma(priv);
+	stmmac_mac_set(priv, priv->ioaddr, false);
 
 init_error:
 	free_dma_desc_resources(priv, priv->dma_conf);
 dma_desc_error:
+	stmmac_release_ptp(priv);
 	return ret;
 }
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
index 909219775507..7ecb7addd2ea 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
@@ -108,6 +108,7 @@ int stmmac_xdp_set_prog(struct stmmac_priv *priv, struct bpf_prog *prog,
 	struct bpf_prog *old_prog;
 	bool need_update;
 	bool if_running;
+	int ret;
 
 	if_running = priv->datapath == STMMAC_DATAPATH_RUNNING;
 
@@ -119,25 +120,41 @@ int stmmac_xdp_set_prog(struct stmmac_priv *priv, struct bpf_prog *prog,
 		return -EOPNOTSUPP;
 	}
 
-	if (!prog)
-		xdp_features_clear_redirect_target(dev);
-
 	need_update = !!priv->xdp_prog != !!prog;
 	if (if_running && need_update)
 		stmmac_xdp_release(dev);
 
 	old_prog = xchg(&priv->xdp_prog, prog);
-	if (old_prog)
-		bpf_prog_put(old_prog);
 
 	/* Disable RX SPH for XDP operation */
 	priv->sph_active = priv->sph_capable && !stmmac_xdp_is_enabled(priv);
 
-	if (if_running && need_update)
-		stmmac_xdp_open(dev);
+	if (if_running && need_update) {
+		ret = stmmac_xdp_open(dev);
+		if (ret) {
+			netdev_err(dev, "failed reopening after XDP change: %pe; interface remains detached\n",
+				   ERR_PTR(ret));
+			if (prog) {
+				/* The core retains the old program on error and drops
+				 * the reference it passed for the proposed program.
+				 */
+				xchg(&priv->xdp_prog, old_prog);
+				priv->sph_active = priv->sph_capable && !old_prog;
+				return ret;
+			}
+			/* Uninstalling a BPF link must release its program even
+			 * if the non-XDP datapath cannot be restarted.
+			 */
+		}
+	}
+
+	if (old_prog)
+		bpf_prog_put(old_prog);
 
 	if (prog)
 		xdp_features_set_redirect_target(dev, false);
+	else
+		xdp_features_clear_redirect_target(dev);
 
 	return 0;
 }

-- 
2.53.0