From: Eelco Chaudron <echaudro@redhat.com>
Date: Wed, 28 Aug 2019 14:49:39 +0000 (-0400)
Subject: vhost: add device op when notification to guest is sent
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=039253166a57ee660dd2fbe92ca77fa65154751c;p=dpdk.git

vhost: add device op when notification to guest is sent

This patch adds an operation callback which gets called every time
the library is waking up the guest trough an eventfd_write() call.

This can be used by 3rd party application, like OVS, to track the
number of times interrupts where generated. This might be of
interest to find out system-call were called in the fast path.

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---

diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
index 7fb172912a..878e339550 100644
--- a/lib/librte_vhost/rte_vhost.h
+++ b/lib/librte_vhost/rte_vhost.h
@@ -172,7 +172,15 @@ struct vhost_device_ops {
 	int (*new_connection)(int vid);
 	void (*destroy_connection)(int vid);
 
-	void *reserved[2]; /**< Reserved for future extension */
+	/**
+	 * This callback gets called each time a guest gets notified
+	 * about waiting packets. This is the interrupt handling trough
+	 * the eventfd_write(callfd), which can be used for counting these
+	 * "slow" syscalls.
+	 */
+	void (*guest_notified)(int vid);
+
+	void *reserved[1]; /**< Reserved for future extension */
 };
 
 /**
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 884befa858..5131a97a39 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -543,13 +543,19 @@ vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
 
 		if ((vhost_need_event(vhost_used_event(vq), new, old) &&
 					(vq->callfd >= 0)) ||
-				unlikely(!signalled_used_valid))
+				unlikely(!signalled_used_valid)) {
 			eventfd_write(vq->callfd, (eventfd_t) 1);
+			if (dev->notify_ops->guest_notified)
+				dev->notify_ops->guest_notified(dev->vid);
+		}
 	} else {
 		/* Kick the guest if necessary. */
 		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-				&& (vq->callfd >= 0))
+				&& (vq->callfd >= 0)) {
 			eventfd_write(vq->callfd, (eventfd_t)1);
+			if (dev->notify_ops->guest_notified)
+				dev->notify_ops->guest_notified(dev->vid);
+		}
 	}
 }
 
@@ -600,8 +606,11 @@ vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	if (vhost_need_event(off, new, old))
 		kick = true;
 kick:
-	if (kick)
+	if (kick) {
 		eventfd_write(vq->callfd, (eventfd_t)1);
+		if (dev->notify_ops->guest_notified)
+			dev->notify_ops->guest_notified(dev->vid);
+	}
 }
 
 static __rte_always_inline void