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, 25 insertions, 2 deletions

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index b249f2d6b0cc..adb7260e94b2 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -323,6 +323,8 @@ 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;
 }
@@ -568,18 +570,28 @@ 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;
 	}
@@ -908,6 +920,7 @@ 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);
 
@@ -918,6 +931,11 @@ 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;
 		}
@@ -1581,6 +1599,7 @@ 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)
@@ -1610,6 +1629,10 @@ 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);