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Subject[PATCH 5/7] xen/events: add per-xenbus device event statistics and settings
Date
Add sysfs 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>
---
drivers/xen/events/events_base.c | 27 ++++++++++++-
drivers/xen/xenbus/xenbus_probe.c | 66 +++++++++++++++++++++++++++++++
include/xen/xenbus.h | 7 ++++
3 files changed, 98 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 8c620c11e32a..d0c57c5664c0 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -327,6 +327,8 @@ static int xen_irq_info_evtchn_setup(unsigned irq,

ret = xen_irq_info_common_setup(info, irq, IRQT_EVTCHN, evtchn, 0);
info->u.interdomain = dev;
+ if (dev)
+ atomic_inc(&dev->event_channels);

return ret;
}
@@ -572,18 +574,28 @@ static void xen_irq_lateeoi_locked(struct irq_info *info, bool spurious)
return;

if (spurious) {
+ struct xenbus_device *dev = info->u.interdomain;
+ unsigned int threshold = 1;
+
+ if (dev && dev->spurious_threshold)
+ threshold = dev->spurious_threshold;
+
if ((1 << info->spurious_cnt) < (HZ << 2)) {
if (info->spurious_cnt != 0xFF)
info->spurious_cnt++;
}
- if (info->spurious_cnt > 1) {
- delay = 1 << (info->spurious_cnt - 2);
+ if (info->spurious_cnt > threshold) {
+ delay = 1 << (info->spurious_cnt - 1 - threshold);
if (delay > HZ)
delay = HZ;
if (!info->eoi_time)
info->eoi_cpu = smp_processor_id();
info->eoi_time = get_jiffies_64() + delay;
+ if (dev)
+ atomic_add(delay, &dev->jiffies_eoi_delayed);
}
+ if (dev)
+ atomic_inc(&dev->spurious_events);
} else {
info->spurious_cnt = 0;
}
@@ -920,6 +932,7 @@ static void __unbind_from_irq(unsigned int irq)

if (VALID_EVTCHN(evtchn)) {
unsigned int cpu = cpu_from_irq(irq);
+ struct xenbus_device *dev;

xen_evtchn_close(evtchn);

@@ -930,6 +943,11 @@ static void __unbind_from_irq(unsigned int irq)
case IRQT_IPI:
per_cpu(ipi_to_irq, cpu)[ipi_from_irq(irq)] = -1;
break;
+ case IRQT_EVTCHN:
+ dev = info->u.interdomain;
+ if (dev)
+ atomic_dec(&dev->event_channels);
+ break;
default:
break;
}
@@ -1593,6 +1611,7 @@ void handle_irq_for_port(evtchn_port_t port, struct evtchn_loop_ctrl *ctrl)
{
int irq;
struct irq_info *info;
+ struct xenbus_device *dev;

irq = get_evtchn_to_irq(port);
if (irq == -1)
@@ -1622,6 +1641,10 @@ void handle_irq_for_port(evtchn_port_t port, struct evtchn_loop_ctrl *ctrl)

info = info_for_irq(irq);

+ dev = (info->type == IRQT_EVTCHN) ? info->u.interdomain : NULL;
+ if (dev)
+ atomic_inc(&dev->events);
+
if (ctrl->defer_eoi) {
info->eoi_cpu = smp_processor_id();
info->irq_epoch = __this_cpu_read(irq_epoch);
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 18ffd0551b54..9494ecad3c92 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) {
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 2c43b0ef1e4d..13ee375a1f05 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -88,6 +88,13 @@ struct xenbus_device {
struct completion down;
struct work_struct work;
struct semaphore reclaim_sem;
+
+ /* Event channel based statistics and settings. */
+ atomic_t event_channels;
+ atomic_t events;
+ atomic_t spurious_events;
+ atomic_t jiffies_eoi_delayed;
+ unsigned int spurious_threshold;
};

static inline struct xenbus_device *to_xenbus_device(struct device *dev)
--
2.26.2
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