xen/events: add per-xenbus device event statistics and settings

Add syfs nodes for each xenbus device showing event statistics (number
of events and spurious events, number of associated event channels)
and for setting a spurious event threshold in case a frontend is
sending too many events without being rogue on purpose.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210219154030.10892-7-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 8a75092bb148..97f0d234482d 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -206,6 +206,65 @@ void xenbus_otherend_changed(struct xenbus_watch *watch,
 }
 EXPORT_SYMBOL_GPL(xenbus_otherend_changed);
 
+#define XENBUS_SHOW_STAT(name)						\
+static ssize_t show_##name(struct device *_dev,				\
+			   struct device_attribute *attr,		\
+			   char *buf)					\
+{									\
+	struct xenbus_device *dev = to_xenbus_device(_dev);		\
+									\
+	return sprintf(buf, "%d\n", atomic_read(&dev->name));		\
+}									\
+static DEVICE_ATTR(name, 0444, show_##name, NULL)
+
+XENBUS_SHOW_STAT(event_channels);
+XENBUS_SHOW_STAT(events);
+XENBUS_SHOW_STAT(spurious_events);
+XENBUS_SHOW_STAT(jiffies_eoi_delayed);
+
+static ssize_t show_spurious_threshold(struct device *_dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+
+	return sprintf(buf, "%d\n", dev->spurious_threshold);
+}
+
+static ssize_t set_spurious_threshold(struct device *_dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+	unsigned int val;
+	ssize_t ret;
+
+	ret = kstrtouint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	dev->spurious_threshold = val;
+
+	return count;
+}
+
+static DEVICE_ATTR(spurious_threshold, 0644, show_spurious_threshold,
+		   set_spurious_threshold);
+
+static struct attribute *xenbus_attrs[] = {
+	&dev_attr_event_channels.attr,
+	&dev_attr_events.attr,
+	&dev_attr_spurious_events.attr,
+	&dev_attr_jiffies_eoi_delayed.attr,
+	&dev_attr_spurious_threshold.attr,
+	NULL
+};
+
+static const struct attribute_group xenbus_group = {
+	.name = "xenbus",
+	.attrs = xenbus_attrs,
+};
+
 int xenbus_dev_probe(struct device *_dev)
 {
 	struct xenbus_device *dev = to_xenbus_device(_dev);
@@ -253,6 +312,11 @@ int xenbus_dev_probe(struct device *_dev)
 		return err;
 	}
 
+	dev->spurious_threshold = 1;
+	if (sysfs_create_group(&dev->dev.kobj, &xenbus_group))
+		dev_warn(&dev->dev, "sysfs_create_group on %s failed.\n",
+			 dev->nodename);
+
 	return 0;
 fail_put:
 	module_put(drv->driver.owner);
@@ -269,6 +333,8 @@ int xenbus_dev_remove(struct device *_dev)
 
 	DPRINTK("%s", dev->nodename);
 
+	sysfs_remove_group(&dev->dev.kobj, &xenbus_group);
+
 	free_otherend_watch(dev);
 
 	if (drv->remove) {