hwtracing: hisi_ptt: Add support for dynamically updating the filter list

The PCIe devices supported by the PTT trace can be removed/rescanned by
hotplug or through sysfs.  Add support for dynamically updating the
available filter list by registering a PCI bus notifier block. Then user
can always get latest information about available tracing filters and
driver can block the invalid filters of which related devices no longer
exist in the system.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230621092804.15120-3-yangyicong@huawei.com

Documentation/trace/hisi-ptt.rst

@@ -153,9 +153,9 @@ Endpoint function can be specified in one trace. Specifying both Root Port
 and function at the same time is not supported. Driver maintains a list of
 available filters and will check the invalid inputs.
 
-Currently the available filters are detected in driver's probe. If the supported
-devices are removed/added after probe, you may need to reload the driver to update
-the filters.
+The available filters will be dynamically updated, which means you will always
+get correct filter information when hotplug events happen, or when you manually
+remove/rescan the devices.
 
 2. Type
 -------

drivers/hwtracing/ptt/hisi_ptt.c

@@ -357,24 +357,42 @@ static int hisi_ptt_register_irq(struct hisi_ptt *hisi_ptt)
 static void hisi_ptt_del_free_filter(struct hisi_ptt *hisi_ptt,
 				      struct hisi_ptt_filter_desc *filter)
 {
+	if (filter->is_port)
+		hisi_ptt->port_mask &= ~hisi_ptt_get_filter_val(filter->devid, true);
+
 	list_del(&filter->list);
+	kfree(filter->name);
 	kfree(filter);
 }
 
 static struct hisi_ptt_filter_desc *
-hisi_ptt_alloc_add_filter(struct hisi_ptt *hisi_ptt, struct pci_dev *pdev)
+hisi_ptt_alloc_add_filter(struct hisi_ptt *hisi_ptt, u16 devid, bool is_port)
 {
 	struct hisi_ptt_filter_desc *filter;
+	u8 devfn = devid & 0xff;
+	char *filter_name;
+
+	filter_name = kasprintf(GFP_KERNEL, "%04x:%02x:%02x.%d", pci_domain_nr(hisi_ptt->pdev->bus),
+				 PCI_BUS_NUM(devid), PCI_SLOT(devfn), PCI_FUNC(devfn));
+	if (!filter_name) {
+		pci_err(hisi_ptt->pdev, "failed to allocate name for filter %04x:%02x:%02x.%d\n",
+			pci_domain_nr(hisi_ptt->pdev->bus), PCI_BUS_NUM(devid),
+			PCI_SLOT(devfn), PCI_FUNC(devfn));
+		return NULL;
+	}
 
 	filter = kzalloc(sizeof(*filter), GFP_KERNEL);
 	if (!filter) {
 		pci_err(hisi_ptt->pdev, "failed to add filter for %s\n",
-			pci_name(pdev));
+			filter_name);
+		kfree(filter_name);
 		return NULL;
 	}
 
-	filter->devid = PCI_DEVID(pdev->bus->number, pdev->devfn);
-	filter->is_port = pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT;
+	filter->name = filter_name;
+	filter->is_port = is_port;
+	filter->devid = devid;
+
 	if (filter->is_port) {
 		list_add_tail(&filter->list, &hisi_ptt->port_filters);
 
@@ -387,6 +405,102 @@ hisi_ptt_alloc_add_filter(struct hisi_ptt *hisi_ptt, struct pci_dev *pdev)
 	return filter;
 }
 
+static void hisi_ptt_update_filters(struct work_struct *work)
+{
+	struct delayed_work *delayed_work = to_delayed_work(work);
+	struct hisi_ptt_filter_update_info info;
+	struct hisi_ptt_filter_desc *filter;
+	struct hisi_ptt *hisi_ptt;
+
+	hisi_ptt = container_of(delayed_work, struct hisi_ptt, work);
+
+	if (!mutex_trylock(&hisi_ptt->filter_lock)) {
+		schedule_delayed_work(&hisi_ptt->work, HISI_PTT_WORK_DELAY_MS);
+		return;
+	}
+
+	while (kfifo_get(&hisi_ptt->filter_update_kfifo, &info)) {
+		if (info.is_add) {
+			/*
+			 * Notify the users if failed to add this filter, others
+			 * still work and available. See the comments in
+			 * hisi_ptt_init_filters().
+			 */
+			filter = hisi_ptt_alloc_add_filter(hisi_ptt, info.devid, info.is_port);
+			if (!filter)
+				continue;
+		} else {
+			struct hisi_ptt_filter_desc *tmp;
+			struct list_head *target_list;
+
+			target_list = info.is_port ? &hisi_ptt->port_filters :
+				      &hisi_ptt->req_filters;
+
+			list_for_each_entry_safe(filter, tmp, target_list, list)
+				if (filter->devid == info.devid) {
+					hisi_ptt_del_free_filter(hisi_ptt, filter);
+					break;
+				}
+		}
+	}
+
+	mutex_unlock(&hisi_ptt->filter_lock);
+}
+
+/*
+ * A PCI bus notifier is used here for dynamically updating the filter
+ * list.
+ */
+static int hisi_ptt_notifier_call(struct notifier_block *nb, unsigned long action,
+				  void *data)
+{
+	struct hisi_ptt *hisi_ptt = container_of(nb, struct hisi_ptt, hisi_ptt_nb);
+	struct hisi_ptt_filter_update_info info;
+	struct pci_dev *pdev, *root_port;
+	struct device *dev = data;
+	u32 port_devid;
+
+	pdev = to_pci_dev(dev);
+	root_port = pcie_find_root_port(pdev);
+	if (!root_port)
+		return 0;
+
+	port_devid = PCI_DEVID(root_port->bus->number, root_port->devfn);
+	if (port_devid < hisi_ptt->lower_bdf ||
+	    port_devid > hisi_ptt->upper_bdf)
+		return 0;
+
+	info.is_port = pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT;
+	info.devid = PCI_DEVID(pdev->bus->number, pdev->devfn);
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		info.is_add = true;
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		info.is_add = false;
+		break;
+	default:
+		return 0;
+	}
+
+	/*
+	 * The FIFO size is 16 which is sufficient for almost all the cases,
+	 * since each PCIe core will have most 8 Root Ports (typically only
+	 * 1~4 Root Ports). On failure log the failed filter and let user
+	 * handle it.
+	 */
+	if (kfifo_in_spinlocked(&hisi_ptt->filter_update_kfifo, &info, 1,
+				&hisi_ptt->filter_update_lock))
+		schedule_delayed_work(&hisi_ptt->work, 0);
+	else
+		pci_warn(hisi_ptt->pdev,
+			 "filter update fifo overflow for target %s\n",
+			 pci_name(pdev));
+
+	return 0;
+}
+
 static int hisi_ptt_init_filters(struct pci_dev *pdev, void *data)
 {
 	struct pci_dev *root_port = pcie_find_root_port(pdev);
@@ -407,7 +521,8 @@ static int hisi_ptt_init_filters(struct pci_dev *pdev, void *data)
 	 * should be partial initialized and users would know which filter fails
 	 * through the log. Other functions of PTT device are still available.
 	 */
-	filter = hisi_ptt_alloc_add_filter(hisi_ptt, pdev);
+	filter = hisi_ptt_alloc_add_filter(hisi_ptt, PCI_DEVID(pdev->bus->number, pdev->devfn),
+					    pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT);
 	if (!filter)
 		return -ENOMEM;
 
@@ -466,8 +581,13 @@ static int hisi_ptt_init_ctrls(struct hisi_ptt *hisi_ptt)
 	int ret;
 	u32 reg;
 
+	INIT_DELAYED_WORK(&hisi_ptt->work, hisi_ptt_update_filters);
+	INIT_KFIFO(hisi_ptt->filter_update_kfifo);
+	spin_lock_init(&hisi_ptt->filter_update_lock);
+
 	INIT_LIST_HEAD(&hisi_ptt->port_filters);
 	INIT_LIST_HEAD(&hisi_ptt->req_filters);
+	mutex_init(&hisi_ptt->filter_lock);
 
 	ret = hisi_ptt_config_trace_buf(hisi_ptt);
 	if (ret)
@@ -620,6 +740,7 @@ static int hisi_ptt_trace_valid_filter(struct hisi_ptt *hisi_ptt, u64 config)
 {
 	unsigned long val, port_mask = hisi_ptt->port_mask;
 	struct hisi_ptt_filter_desc *filter;
+	int ret = 0;
 
 	hisi_ptt->trace_ctrl.is_port = FIELD_GET(HISI_PTT_PMU_FILTER_IS_PORT, config);
 	val = FIELD_GET(HISI_PTT_PMU_FILTER_VAL_MASK, config);
@@ -633,16 +754,20 @@ static int hisi_ptt_trace_valid_filter(struct hisi_ptt *hisi_ptt, u64 config)
 	 * For Requester ID filters, walk the available filter list to see
 	 * whether we have one matched.
 	 */
+	mutex_lock(&hisi_ptt->filter_lock);
 	if (!hisi_ptt->trace_ctrl.is_port) {
 		list_for_each_entry(filter, &hisi_ptt->req_filters, list) {
 			if (val == hisi_ptt_get_filter_val(filter->devid, filter->is_port))
-				return 0;
+				goto out;
 		}
 	} else if (bitmap_subset(&val, &port_mask, BITS_PER_LONG)) {
-		return 0;
+		goto out;
 	}
 
-	return -EINVAL;
+	ret = -EINVAL;
+out:
+	mutex_unlock(&hisi_ptt->filter_lock);
+	return ret;
 }
 
 static void hisi_ptt_pmu_init_configs(struct hisi_ptt *hisi_ptt, struct perf_event *event)
@@ -916,6 +1041,31 @@ static int hisi_ptt_register_pmu(struct hisi_ptt *hisi_ptt)
 					&hisi_ptt->hisi_ptt_pmu);
 }
 
+static void hisi_ptt_unregister_filter_update_notifier(void *data)
+{
+	struct hisi_ptt *hisi_ptt = data;
+
+	bus_unregister_notifier(&pci_bus_type, &hisi_ptt->hisi_ptt_nb);
+
+	/* Cancel any work that has been queued */
+	cancel_delayed_work_sync(&hisi_ptt->work);
+}
+
+/* Register the bus notifier for dynamically updating the filter list */
+static int hisi_ptt_register_filter_update_notifier(struct hisi_ptt *hisi_ptt)
+{
+	int ret;
+
+	hisi_ptt->hisi_ptt_nb.notifier_call = hisi_ptt_notifier_call;
+	ret = bus_register_notifier(&pci_bus_type, &hisi_ptt->hisi_ptt_nb);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(&hisi_ptt->pdev->dev,
+					hisi_ptt_unregister_filter_update_notifier,
+					hisi_ptt);
+}
+
 /*
  * The DMA of PTT trace can only use direct mappings due to some
  * hardware restriction. Check whether there is no IOMMU or the
@@ -987,6 +1137,10 @@ static int hisi_ptt_probe(struct pci_dev *pdev,
 		return ret;
 	}
 
+	ret = hisi_ptt_register_filter_update_notifier(hisi_ptt);
+	if (ret)
+		pci_warn(pdev, "failed to register filter update notifier, ret = %d", ret);
+
 	ret = hisi_ptt_register_pmu(hisi_ptt);
 	if (ret) {
 		pci_err(pdev, "failed to register PMU device, ret = %d", ret);

drivers/hwtracing/ptt/hisi_ptt.h

@@ -11,12 +11,15 @@
 
 #include <linux/bits.h>
 #include <linux/cpumask.h>
+#include <linux/kfifo.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
+#include <linux/notifier.h>
 #include <linux/pci.h>
 #include <linux/perf_event.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 #define DRV_NAME "hisi_ptt"
 
@@ -71,6 +74,11 @@
 #define HISI_PTT_WAIT_TRACE_TIMEOUT_US	100UL
 #define HISI_PTT_WAIT_POLL_INTERVAL_US	10UL
 
+/* FIFO size for dynamically updating the PTT trace filter list. */
+#define HISI_PTT_FILTER_UPDATE_FIFO_SIZE	16
+/* Delay time for filter updating work */
+#define HISI_PTT_WORK_DELAY_MS			100UL
+
 #define HISI_PCIE_CORE_PORT_ID(devfn)	((PCI_SLOT(devfn) & 0x7) << 1)
 
 /* Definition of the PMU configs */
@@ -135,11 +143,25 @@ struct hisi_ptt_trace_ctrl {
  * struct hisi_ptt_filter_desc - Descriptor of the PTT trace filter
  * @list:    entry of this descriptor in the filter list
  * @is_port: the PCI device of the filter is a Root Port or not
+ * @name:    name of this filter, same as the name of the related PCI device
  * @devid:   the PCI device's devid of the filter
  */
 struct hisi_ptt_filter_desc {
 	struct list_head list;
 	bool is_port;
+	char *name;
+	u16 devid;
+};
+
+/**
+ * struct hisi_ptt_filter_update_info - Information for PTT filter updating
+ * @is_port:    the PCI device to update is a Root Port or not
+ * @is_add:     adding to the filter or not
+ * @devid:      the PCI device's devid of the filter
+ */
+struct hisi_ptt_filter_update_info {
+	bool is_port;
+	bool is_add;
 	u16 devid;
 };
 
@@ -160,6 +182,7 @@ struct hisi_ptt_pmu_buf {
 /**
  * struct hisi_ptt - Per PTT device data
  * @trace_ctrl:   the control information of PTT trace
+ * @hisi_ptt_nb:  dynamic filter update notifier
  * @hotplug_node: node for register cpu hotplug event
  * @hisi_ptt_pmu: the pum device of trace
  * @iobase:       base IO address of the device
@@ -170,10 +193,15 @@ struct hisi_ptt_pmu_buf {
  * @lower_bdf:    the lower BDF range of the PCI devices managed by this PTT device
  * @port_filters: the filter list of root ports
  * @req_filters:  the filter list of requester ID
+ * @filter_lock:  lock to protect the filters
  * @port_mask:    port mask of the managed root ports
+ * @work:         delayed work for filter updating
+ * @filter_update_lock: spinlock to protect the filter update fifo
+ * @filter_update_fifo: fifo of the filters waiting to update the filter list
  */
 struct hisi_ptt {
 	struct hisi_ptt_trace_ctrl trace_ctrl;
+	struct notifier_block hisi_ptt_nb;
 	struct hlist_node hotplug_node;
 	struct pmu hisi_ptt_pmu;
 	void __iomem *iobase;
@@ -192,7 +220,19 @@ struct hisi_ptt {
 	 */
 	struct list_head port_filters;
 	struct list_head req_filters;
+	struct mutex filter_lock;
 	u16 port_mask;
+
+	/*
+	 * We use a delayed work here to avoid indefinitely waiting for
+	 * the hisi_ptt->mutex which protecting the filter list. The
+	 * work will be delayed only if the mutex can not be held,
+	 * otherwise no delay will be applied.
+	 */
+	struct delayed_work work;
+	spinlock_t filter_update_lock;
+	DECLARE_KFIFO(filter_update_kfifo, struct hisi_ptt_filter_update_info,
+		      HISI_PTT_FILTER_UPDATE_FIFO_SIZE);
 };
 
 #define to_hisi_ptt(pmu) container_of(pmu, struct hisi_ptt, hisi_ptt_pmu)