[PATCH v4 12/26] vhost: add helper for interrupt injection

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Vhost-user uses eventfd to inject IRQs, but VDUSE uses
an ioctl.

This patch prepares vhost_vring_call_split() and
vhost_vring_call_packed() to support VDUSE by introducing
a new helper.

It also adds a new counter for guest notification failures,
which could happen in case of uninitialized call file
descriptor for example.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
 lib/vhost/vhost.c      | 25 +++++++++++++------------
 lib/vhost/vhost.h      | 19 +++++++++----------
 lib/vhost/vhost_user.c | 10 ++++++++++
 3 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index f77f30d674..eb6309b681 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -701,6 +701,11 @@ vhost_new_device(struct vhost_backend_ops *ops)
 		return -1;
 	}
 
+	if (ops->inject_irq == NULL) {
+		VHOST_LOG_CONFIG("device", ERR, "missing IRQ injection backend op.\n");
+		return -1;
+	}
+
 	pthread_mutex_lock(&vhost_dev_lock);
 	for (i = 0; i < RTE_MAX_VHOST_DEVICE; i++) {
 		if (vhost_devices[i] == NULL)
@@ -1511,20 +1516,16 @@ rte_vhost_notify_guest(int vid, uint16_t queue_id)
 
 	rte_rwlock_read_lock(&vq->access_lock);
 
-	if (vq->callfd >= 0) {
-		int ret = eventfd_write(vq->callfd, (eventfd_t)1);
-
-		if (ret) {
-			if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
-				__atomic_fetch_add(&vq->stats.guest_notifications_error,
+	if (dev->backend_ops->inject_irq(dev, vq)) {
+		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
+			__atomic_fetch_add(&vq->stats.guest_notifications_error,
 					1, __ATOMIC_RELAXED);
-		} else {
-			if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
-				__atomic_fetch_add(&vq->stats.guest_notifications,
+	} else {
+		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
+			__atomic_fetch_add(&vq->stats.guest_notifications,
 					1, __ATOMIC_RELAXED);
-			if (dev->notify_ops->guest_notified)
-				dev->notify_ops->guest_notified(dev->vid);
-		}
+		if (dev->notify_ops->guest_notified)
+			dev->notify_ops->guest_notified(dev->vid);
 	}
 
 	rte_rwlock_read_unlock(&vq->access_lock);
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index 25255aaea8..ea2798b0bf 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -90,16 +90,20 @@
 #endif
 
 struct virtio_net;
+struct vhost_virtqueue;
+
 typedef void (*vhost_iotlb_remove_notify)(uint64_t addr, uint64_t off, uint64_t size);
 
 typedef int (*vhost_iotlb_miss_cb)(struct virtio_net *dev, uint64_t iova, uint8_t perm);
 
+typedef int (*vhost_vring_inject_irq_cb)(struct virtio_net *dev, struct vhost_virtqueue *vq);
 /**
  * Structure that contains backend-specific ops.
  */
 struct vhost_backend_ops {
 	vhost_iotlb_remove_notify iotlb_remove_notify;
 	vhost_iotlb_miss_cb iotlb_miss;
+	vhost_vring_inject_irq_cb inject_irq;
 };
 
 /**
@@ -906,8 +910,6 @@ vhost_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
 static __rte_always_inline void
 vhost_vring_inject_irq(struct virtio_net *dev, struct vhost_virtqueue *vq)
 {
-	int ret;
-
 	if (dev->notify_ops->guest_notify &&
 	    dev->notify_ops->guest_notify(dev->vid, vq->index)) {
 		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
@@ -916,8 +918,7 @@ vhost_vring_inject_irq(struct virtio_net *dev, struct vhost_virtqueue *vq)
 		return;
 	}
 
-	ret = eventfd_write(vq->callfd, (eventfd_t) 1);
-	if (ret) {
+	if (dev->backend_ops->inject_irq(dev, vq)) {
 		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
 			__atomic_fetch_add(&vq->stats.guest_notifications_error,
 				1, __ATOMIC_RELAXED);
@@ -950,14 +951,12 @@ vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
 			"%s: used_event_idx=%d, old=%d, new=%d\n",
 			__func__, vhost_used_event(vq), old, new);
 
-		if ((vhost_need_event(vhost_used_event(vq), new, old) ||
-					unlikely(!signalled_used_valid)) &&
-				vq->callfd >= 0)
+		if (vhost_need_event(vhost_used_event(vq), new, old) ||
+				unlikely(!signalled_used_valid))
 			vhost_vring_inject_irq(dev, vq);
 	} else {
 		/* Kick the guest if necessary. */
-		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT) &&
-				(vq->callfd >= 0))
+		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
 			vhost_vring_inject_irq(dev, vq);
 	}
 }
@@ -1009,7 +1008,7 @@ vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	if (vhost_need_event(off, new, old))
 		kick = true;
 kick:
-	if (kick && vq->callfd >= 0)
+	if (kick)
 		vhost_vring_inject_irq(dev, vq);
 }
 
diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 30ad63aba0..901a80bbaa 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -3465,8 +3465,18 @@ int rte_vhost_host_notifier_ctrl(int vid, uint16_t qid, bool enable)
 	return ret;
 }
 
+static int
+vhost_user_inject_irq(struct virtio_net *dev __rte_unused, struct vhost_virtqueue *vq)
+{
+	if (vq->callfd < 0)
+		return -1;
+
+	return eventfd_write(vq->callfd, (eventfd_t)1);
+}
+
 static struct vhost_backend_ops vhost_user_backend_ops = {
 	.iotlb_miss = vhost_user_iotlb_miss,
+	.inject_irq = vhost_user_inject_irq,
 };
 
 int
-- 
2.40.1