sfc: Rework IRQ enable/disable

There are many problems with the current efx_stop_interrupts() and
efx_start_interrupts():

1. On Siena, it is unsafe to disable the master IRQ enable bit
(DRV_INT_EN_KER) while any IRQ sources are enabled.

2. On EF10 there is no master IRQ enable bit, so we cannot expect to
defer IRQs without tearing down event queues.  (Though I don't think
we will need to keep any event queues around while the device is down,
as we do for VFDI on Siena.)

3. synchronize_irq() only waits for a running IRQ handler to finish,
not for any propagation through IRQ controllers.  Therefore an IRQ may
still be received and handled after efx_stop_interrupts() returns.
IRQ handlers can then race with channel reallocation.

To fix this:

a. Introduce a software IRQ enable flag.  So long as this is clear,
IRQ handlers will only acknowledge IRQs and not touch the channel
structures.

b. Define a new struct efx_msi_context as the context for MSIs.  This
is never reallocated and is sufficient to find the software enable
flag and the channel structure.  It also includes the channel/IRQ
name, which was previously separated out as it must also not be
reallocated.

c. Split efx_{start,stop}_interrupts() into
efx_{,soft_}_{enable,disable}_interrupts().  The 'soft' functions
don't touch the hardware master enable flag (if it exists) and don't
reinitialise or tear down channels with the keep_eventq flag set.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

4 files changed, 112 insertions, 59 deletions

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 2b2dba1a0676..a7818d1c2415 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -191,8 +191,8 @@ MODULE_PARM_DESC(debug, "Bitmapped debugging message enable value");
  *
  *************************************************************************/
 
-static void efx_start_interrupts(struct efx_nic *efx, bool may_keep_eventq);
-static void efx_stop_interrupts(struct efx_nic *efx, bool may_keep_eventq);
+static void efx_soft_enable_interrupts(struct efx_nic *efx);
+static void efx_soft_disable_interrupts(struct efx_nic *efx);
 static void efx_remove_channel(struct efx_channel *channel);
 static void efx_remove_channels(struct efx_nic *efx);
 static const struct efx_channel_type efx_default_channel_type;
@@ -520,8 +520,8 @@ static void efx_set_channel_names(struct efx_nic *efx)
 
 	efx_for_each_channel(channel, efx)
 		channel->type->get_name(channel,
-					efx->channel_name[channel->channel],
-					sizeof(efx->channel_name[0]));
+					efx->msi_context[channel->channel].name,
+					sizeof(efx->msi_context[0].name));
 }
 
 static int efx_probe_channels(struct efx_nic *efx)
@@ -746,7 +746,7 @@ efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries)
 
 	efx_device_detach_sync(efx);
 	efx_stop_all(efx);
-	efx_stop_interrupts(efx, true);
+	efx_soft_disable_interrupts(efx);
 
 	/* Clone channels (where possible) */
 	memset(other_channel, 0, sizeof(other_channel));
@@ -796,7 +796,7 @@ out:
 		}
 	}
 
-	efx_start_interrupts(efx, true);
+	efx_soft_enable_interrupts(efx);
 	efx_start_all(efx);
 	netif_device_attach(efx->net_dev);
 	return rc;
@@ -1329,23 +1329,17 @@ static int efx_probe_interrupts(struct efx_nic *efx)
 	return 0;
 }
 
-/* Enable interrupts, then probe and start the event queues */
-static void efx_start_interrupts(struct efx_nic *efx, bool may_keep_eventq)
+static void efx_soft_enable_interrupts(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
 
 	BUG_ON(efx->state == STATE_DISABLED);
 
-	if (efx->eeh_disabled_legacy_irq) {
-		enable_irq(efx->legacy_irq);
-		efx->eeh_disabled_legacy_irq = false;
-	}
-	if (efx->legacy_irq)
-		efx->legacy_irq_enabled = true;
-	efx_nic_enable_interrupts(efx);
+	efx->irq_soft_enabled = true;
+	smp_wmb();
 
 	efx_for_each_channel(channel, efx) {
-		if (!channel->type->keep_eventq || !may_keep_eventq)
+		if (!channel->type->keep_eventq)
 			efx_init_eventq(channel);
 		efx_start_eventq(channel);
 	}
@@ -1353,7 +1347,7 @@ static void efx_start_interrupts(struct efx_nic *efx, bool may_keep_eventq)
 	efx_mcdi_mode_event(efx);
 }
 
-static void efx_stop_interrupts(struct efx_nic *efx, bool may_keep_eventq)
+static void efx_soft_disable_interrupts(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
 
@@ -1362,22 +1356,57 @@ static void efx_stop_interrupts(struct efx_nic *efx, bool may_keep_eventq)
 
 	efx_mcdi_mode_poll(efx);
 
-	efx_nic_disable_interrupts(efx);
-	if (efx->legacy_irq) {
+	efx->irq_soft_enabled = false;
+	smp_wmb();
+
+	if (efx->legacy_irq)
 		synchronize_irq(efx->legacy_irq);
-		efx->legacy_irq_enabled = false;
-	}
 
 	efx_for_each_channel(channel, efx) {
 		if (channel->irq)
 			synchronize_irq(channel->irq);
 
 		efx_stop_eventq(channel);
-		if (!channel->type->keep_eventq || !may_keep_eventq)
+		if (!channel->type->keep_eventq)
 			efx_fini_eventq(channel);
 	}
 }
 
+static void efx_enable_interrupts(struct efx_nic *efx)
+{
+	struct efx_channel *channel;
+
+	BUG_ON(efx->state == STATE_DISABLED);
+
+	if (efx->eeh_disabled_legacy_irq) {
+		enable_irq(efx->legacy_irq);
+		efx->eeh_disabled_legacy_irq = false;
+	}
+
+	efx_nic_enable_interrupts(efx);
+
+	efx_for_each_channel(channel, efx) {
+		if (channel->type->keep_eventq)
+			efx_init_eventq(channel);
+	}
+
+	efx_soft_enable_interrupts(efx);
+}
+
+static void efx_disable_interrupts(struct efx_nic *efx)
+{
+	struct efx_channel *channel;
+
+	efx_soft_disable_interrupts(efx);
+
+	efx_for_each_channel(channel, efx) {
+		if (channel->type->keep_eventq)
+			efx_fini_eventq(channel);
+	}
+
+	efx_nic_disable_interrupts(efx);
+}
+
 static void efx_remove_interrupts(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
@@ -2160,7 +2189,7 @@ void efx_reset_down(struct efx_nic *efx, enum reset_type method)
 	EFX_ASSERT_RESET_SERIALISED(efx);
 
 	efx_stop_all(efx);
-	efx_stop_interrupts(efx, false);
+	efx_disable_interrupts(efx);
 
 	mutex_lock(&efx->mac_lock);
 	if (efx->port_initialized && method != RESET_TYPE_INVISIBLE)
@@ -2199,7 +2228,7 @@ int efx_reset_up(struct efx_nic *efx, enum reset_type method, bool ok)
 
 	efx->type->reconfigure_mac(efx);
 
-	efx_start_interrupts(efx, false);
+	efx_enable_interrupts(efx);
 	efx_restore_filters(efx);
 	efx_sriov_reset(efx);
 
@@ -2464,6 +2493,8 @@ static int efx_init_struct(struct efx_nic *efx,
 		efx->channel[i] = efx_alloc_channel(efx, i, NULL);
 		if (!efx->channel[i])
 			goto fail;
+		efx->msi_context[i].efx = efx;
+		efx->msi_context[i].index = i;
 	}
 
 	EFX_BUG_ON_PARANOID(efx->type->phys_addr_channels > EFX_MAX_CHANNELS);
@@ -2516,7 +2547,7 @@ static void efx_pci_remove_main(struct efx_nic *efx)
 	BUG_ON(efx->state == STATE_READY);
 	cancel_work_sync(&efx->reset_work);
 
-	efx_stop_interrupts(efx, false);
+	efx_disable_interrupts(efx);
 	efx_nic_fini_interrupt(efx);
 	efx_fini_port(efx);
 	efx->type->fini(efx);
@@ -2538,7 +2569,7 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
 	/* Mark the NIC as fini, then stop the interface */
 	rtnl_lock();
 	dev_close(efx->net_dev);
-	efx_stop_interrupts(efx, false);
+	efx_disable_interrupts(efx);
 	rtnl_unlock();
 
 	efx_sriov_fini(efx);
@@ -2640,7 +2671,7 @@ static int efx_pci_probe_main(struct efx_nic *efx)
 	rc = efx_nic_init_interrupt(efx);
 	if (rc)
 		goto fail5;
-	efx_start_interrupts(efx, false);
+	efx_enable_interrupts(efx);
 
 	return 0;
 
@@ -2761,7 +2792,7 @@ static int efx_pm_freeze(struct device *dev)
 		efx_device_detach_sync(efx);
 
 		efx_stop_all(efx);
-		efx_stop_interrupts(efx, false);
+		efx_disable_interrupts(efx);
 	}
 
 	rtnl_unlock();
@@ -2776,7 +2807,7 @@ static int efx_pm_thaw(struct device *dev)
 	rtnl_lock();
 
 	if (efx->state != STATE_DISABLED) {
-		efx_start_interrupts(efx, false);
+		efx_enable_interrupts(efx);
 
 		mutex_lock(&efx->mac_lock);
 		efx->phy_op->reconfigure(efx);
@@ -2879,7 +2910,7 @@ static pci_ers_result_t efx_io_error_detected(struct pci_dev *pdev,
 		efx_device_detach_sync(efx);
 
 		efx_stop_all(efx);
-		efx_stop_interrupts(efx, false);
+		efx_disable_interrupts(efx);
 
 		status = PCI_ERS_RESULT_NEED_RESET;
 	} else {
diff --git a/drivers/net/ethernet/sfc/falcon.c b/drivers/net/ethernet/sfc/falcon.c
index f87710e9f8cd..f8de38243348 100644
--- a/drivers/net/ethernet/sfc/falcon.c
+++ b/drivers/net/ethernet/sfc/falcon.c
@@ -367,6 +367,9 @@ irqreturn_t falcon_legacy_interrupt_a1(int irq, void *dev_id)
 		   "IRQ %d on CPU %d status " EFX_OWORD_FMT "\n",
 		   irq, raw_smp_processor_id(), EFX_OWORD_VAL(*int_ker));
 
+	if (!likely(ACCESS_ONCE(efx->irq_soft_enabled)))
+		return IRQ_HANDLED;
+
 	/* Check to see if we have a serious error condition */
 	syserr = EFX_OWORD_FIELD(*int_ker, FSF_AZ_NET_IVEC_FATAL_INT);
 	if (unlikely(syserr))
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index ad89d7d990f5..7c9637203ea0 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -420,6 +420,21 @@ struct efx_channel {
 };
 
 /**
+ * struct efx_msi_context - Context for each MSI
+ * @efx: The associated NIC
+ * @index: Index of the channel/IRQ
+ * @name: Name of the channel/IRQ
+ *
+ * Unlike &struct efx_channel, this is never reallocated and is always
+ * safe for the IRQ handler to access.
+ */
+struct efx_msi_context {
+	struct efx_nic *efx;
+	unsigned int index;
+	char name[IFNAMSIZ + 6];
+};
+
+/**
  * struct efx_channel_type - distinguishes traffic and extra channels
  * @handle_no_channel: Handle failure to allocate an extra channel
  * @pre_probe: Set up extra state prior to initialisation
@@ -669,7 +684,6 @@ struct vfdi_status;
  * @pci_dev: The PCI device
  * @type: Controller type attributes
  * @legacy_irq: IRQ number
- * @legacy_irq_enabled: Are IRQs enabled on NIC (INT_EN_KER register)?
  * @workqueue: Workqueue for port reconfigures and the HW monitor.
  *	Work items do not hold and must not acquire RTNL.
  * @workqueue_name: Name of workqueue
@@ -686,7 +700,7 @@ struct vfdi_status;
  * @tx_queue: TX DMA queues
  * @rx_queue: RX DMA queues
  * @channel: Channels
- * @channel_name: Names for channels and their IRQs
+ * @msi_context: Context for each MSI
  * @extra_channel_types: Types of extra (non-traffic) channels that
  *	should be allocated for this NIC
  * @rxq_entries: Size of receive queues requested by user.
@@ -709,6 +723,8 @@ struct vfdi_status;
  * @rx_scatter: Scatter mode enabled for receives
  * @int_error_count: Number of internal errors seen recently
  * @int_error_expire: Time at which error count will be expired
+ * @irq_soft_enabled: Are IRQs soft-enabled? If not, IRQ handler will
+ *	acknowledge but do nothing else.
  * @irq_status: Interrupt status buffer
  * @irq_zero_count: Number of legacy IRQs seen with queue flags == 0
  * @irq_level: IRQ level/index for IRQs not triggered by an event queue
@@ -786,7 +802,6 @@ struct efx_nic {
 	unsigned int port_num;
 	const struct efx_nic_type *type;
 	int legacy_irq;
-	bool legacy_irq_enabled;
 	bool eeh_disabled_legacy_irq;
 	struct workqueue_struct *workqueue;
 	char workqueue_name[16];
@@ -804,7 +819,7 @@ struct efx_nic {
 	unsigned long reset_pending;
 
 	struct efx_channel *channel[EFX_MAX_CHANNELS];
-	char channel_name[EFX_MAX_CHANNELS][IFNAMSIZ + 6];
+	struct efx_msi_context msi_context[EFX_MAX_CHANNELS];
 	const struct efx_channel_type *
 	extra_channel_type[EFX_MAX_EXTRA_CHANNELS];
 
@@ -835,6 +850,7 @@ struct efx_nic {
 	unsigned int_error_count;
 	unsigned long int_error_expire;
 
+	bool irq_soft_enabled;
 	struct efx_buffer irq_status;
 	unsigned irq_zero_count;
 	unsigned irq_level;
diff --git a/drivers/net/ethernet/sfc/nic.c b/drivers/net/ethernet/sfc/nic.c
index f758333b4d85..c17d659f4525 100644
--- a/drivers/net/ethernet/sfc/nic.c
+++ b/drivers/net/ethernet/sfc/nic.c
@@ -1567,6 +1567,7 @@ irqreturn_t efx_nic_fatal_interrupt(struct efx_nic *efx)
 static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 {
 	struct efx_nic *efx = dev_id;
+	bool soft_enabled = ACCESS_ONCE(efx->irq_soft_enabled);
 	efx_oword_t *int_ker = efx->irq_status.addr;
 	irqreturn_t result = IRQ_NONE;
 	struct efx_channel *channel;
@@ -1574,12 +1575,6 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 	u32 queues;
 	int syserr;
 
-	/* Could this be ours?  If interrupts are disabled then the
-	 * channel state may not be valid.
-	 */
-	if (!efx->legacy_irq_enabled)
-		return result;
-
 	/* Read the ISR which also ACKs the interrupts */
 	efx_readd(efx, &reg, FR_BZ_INT_ISR0);
 	queues = EFX_EXTRACT_DWORD(reg, 0, 31);
@@ -1595,7 +1590,7 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 	}
 
 	/* Handle non-event-queue sources */
-	if (queues & (1U << efx->irq_level)) {
+	if (queues & (1U << efx->irq_level) && soft_enabled) {
 		syserr = EFX_OWORD_FIELD(*int_ker, FSF_AZ_NET_IVEC_FATAL_INT);
 		if (unlikely(syserr))
 			return efx_nic_fatal_interrupt(efx);
@@ -1607,10 +1602,12 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 			efx->irq_zero_count = 0;
 
 		/* Schedule processing of any interrupting queues */
-		efx_for_each_channel(channel, efx) {
-			if (queues & 1)
-				efx_schedule_channel_irq(channel);
-			queues >>= 1;
+		if (likely(soft_enabled)) {
+			efx_for_each_channel(channel, efx) {
+				if (queues & 1)
+					efx_schedule_channel_irq(channel);
+				queues >>= 1;
+			}
 		}
 		result = IRQ_HANDLED;
 
@@ -1623,12 +1620,15 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 			result = IRQ_HANDLED;
 
 		/* Ensure we schedule or rearm all event queues */
-		efx_for_each_channel(channel, efx) {
-			event = efx_event(channel, channel->eventq_read_ptr);
-			if (efx_event_present(event))
-				efx_schedule_channel_irq(channel);
-			else
-				efx_nic_eventq_read_ack(channel);
+		if (likely(soft_enabled)) {
+			efx_for_each_channel(channel, efx) {
+				event = efx_event(channel,
+						  channel->eventq_read_ptr);
+				if (efx_event_present(event))
+					efx_schedule_channel_irq(channel);
+				else
+					efx_nic_eventq_read_ack(channel);
+			}
 		}
 	}
 
@@ -1649,8 +1649,8 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
  */
 static irqreturn_t efx_msi_interrupt(int irq, void *dev_id)
 {
-	struct efx_channel *channel = *(struct efx_channel **)dev_id;
-	struct efx_nic *efx = channel->efx;
+	struct efx_msi_context *context = dev_id;
+	struct efx_nic *efx = context->efx;
 	efx_oword_t *int_ker = efx->irq_status.addr;
 	int syserr;
 
@@ -1658,8 +1658,11 @@ static irqreturn_t efx_msi_interrupt(int irq, void *dev_id)
 		   "IRQ %d on CPU %d status " EFX_OWORD_FMT "\n",
 		   irq, raw_smp_processor_id(), EFX_OWORD_VAL(*int_ker));
 
+	if (!likely(ACCESS_ONCE(efx->irq_soft_enabled)))
+		return IRQ_HANDLED;
+
 	/* Handle non-event-queue sources */
-	if (channel->channel == efx->irq_level) {
+	if (context->index == efx->irq_level) {
 		syserr = EFX_OWORD_FIELD(*int_ker, FSF_AZ_NET_IVEC_FATAL_INT);
 		if (unlikely(syserr))
 			return efx_nic_fatal_interrupt(efx);
@@ -1667,7 +1670,7 @@ static irqreturn_t efx_msi_interrupt(int irq, void *dev_id)
 	}
 
 	/* Schedule processing of the channel */
-	efx_schedule_channel_irq(channel);
+	efx_schedule_channel_irq(efx->channel[context->index]);
 
 	return IRQ_HANDLED;
 }
@@ -1739,8 +1742,8 @@ int efx_nic_init_interrupt(struct efx_nic *efx)
 	efx_for_each_channel(channel, efx) {
 		rc = request_irq(channel->irq, efx_msi_interrupt,
 				 IRQF_PROBE_SHARED, /* Not shared */
-				 efx->channel_name[channel->channel],
-				 &efx->channel[channel->channel]);
+				 efx->msi_context[channel->channel].name,
+				 &efx->msi_context[channel->channel]);
 		if (rc) {
 			netif_err(efx, drv, efx->net_dev,
 				  "failed to hook IRQ %d\n", channel->irq);
@@ -1769,7 +1772,7 @@ int efx_nic_init_interrupt(struct efx_nic *efx)
 	efx_for_each_channel(channel, efx) {
 		if (n_irqs-- == 0)
 			break;
-		free_irq(channel->irq, &efx->channel[channel->channel]);
+		free_irq(channel->irq, &efx->msi_context[channel->channel]);
 	}
  fail1:
 	return rc;
@@ -1787,7 +1790,7 @@ void efx_nic_fini_interrupt(struct efx_nic *efx)
 
 	/* Disable MSI/MSI-X interrupts */
 	efx_for_each_channel(channel, efx)
-		free_irq(channel->irq, &efx->channel[channel->channel]);
+		free_irq(channel->irq, &efx->msi_context[channel->channel]);
 
 	/* ACK legacy interrupt */
 	if (efx_nic_rev(efx) >= EFX_REV_FALCON_B0)