[RFC,14/27] vhost: add helper for interrupt injection

  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 to 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>
---
 lib/vhost/vhost.c      |  6 +++++
 lib/vhost/vhost.h      | 54 +++++++++++++++++++++++-------------------
 lib/vhost/vhost_user.c | 10 ++++++++
 3 files changed, 46 insertions(+), 24 deletions(-)
  

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Friday, March 31, 2023 11:43 PM
> To: dev@dpdk.org; david.marchand@redhat.com; Xia, Chenbo
> <chenbo.xia@intel.com>; mkp@redhat.com; fbl@redhat.com;
> jasowang@redhat.com; Liang, Cunming <cunming.liang@intel.com>; Xie, Yongji
> <xieyongji@bytedance.com>; echaudro@redhat.com; eperezma@redhat.com;
> amorenoz@redhat.com
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Subject: [RFC 14/27] vhost: add helper for interrupt injection
> 
> 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 to for guest notification

to for -> for?

With this fixed:

Reviewed-by: Chenbo Xia <chenbo.xia@intel.com> 

> failures, which could happen in case of uninitialized call
> file descriptor for example.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/vhost/vhost.c      |  6 +++++
>  lib/vhost/vhost.h      | 54 +++++++++++++++++++++++-------------------
>  lib/vhost/vhost_user.c | 10 ++++++++
>  3 files changed, 46 insertions(+), 24 deletions(-)
> 
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 790eb06b28..c07028f2b3 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -44,6 +44,7 @@ static const struct vhost_vq_stats_name_off
> vhost_vq_stat_strings[] = {
>  	{"size_1024_1518_packets", offsetof(struct vhost_virtqueue,
> stats.size_bins[6])},
>  	{"size_1519_max_packets",  offsetof(struct vhost_virtqueue,
> stats.size_bins[7])},
>  	{"guest_notifications",    offsetof(struct vhost_virtqueue,
> stats.guest_notifications)},
> +	{"guest_notifications_error",    offsetof(struct vhost_virtqueue,
> stats.guest_notifications_error)},
>  	{"iotlb_hits",             offsetof(struct vhost_virtqueue,
> stats.iotlb_hits)},
>  	{"iotlb_misses",           offsetof(struct vhost_virtqueue,
> stats.iotlb_misses)},
>  	{"inflight_submitted",     offsetof(struct vhost_virtqueue,
> stats.inflight_submitted)},
> @@ -697,6 +698,11 @@ 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)
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index ee7640e901..8f0875b4e2 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;
>  };
> 
>  /**
> @@ -149,6 +153,7 @@ struct virtqueue_stats {
>  	/* Size bins in array as RFC 2819, undersized [0], 64 [1], etc */
>  	uint64_t size_bins[8];
>  	uint64_t guest_notifications;
> +	uint64_t guest_notifications_error;
>  	uint64_t iotlb_hits;
>  	uint64_t iotlb_misses;
>  	uint64_t inflight_submitted;
> @@ -900,6 +905,24 @@ vhost_need_event(uint16_t event_idx, uint16_t new_idx,
> uint16_t old)
>  	return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx -
> old);
>  }
> 
> +static __rte_always_inline void
> +vhost_vring_inject_irq(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +{
> +	int ret;
> +
> +	ret = dev->backend_ops->inject_irq(dev, vq);
> +	if (ret) {
> +		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> +			vq->stats.guest_notifications_error++;
> +		return;
> +	}
> +
> +	if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> +		vq->stats.guest_notifications++;
> +	if (dev->notify_ops->guest_notified)
> +		dev->notify_ops->guest_notified(dev->vid);
> +}
> +
>  static __rte_always_inline void
>  vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  {
> @@ -919,25 +942,13 @@ 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) {
> -			eventfd_write(vq->callfd, (eventfd_t) 1);
> -			if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> -				vq->stats.guest_notifications++;
> -			if (dev->notify_ops->guest_notified)
> -				dev->notify_ops->guest_notified(dev->vid);
> -		}
> +		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)) {
> -			eventfd_write(vq->callfd, (eventfd_t)1);
> -			if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> -				vq->stats.guest_notifications++;
> -			if (dev->notify_ops->guest_notified)
> -				dev->notify_ops->guest_notified(dev->vid);
> -		}
> +		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
> +			vhost_vring_inject_irq(dev, vq);
>  	}
>  }
> 
> @@ -988,13 +999,8 @@ 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) {
> -		eventfd_write(vq->callfd, (eventfd_t)1);
> -		if (dev->flags & VIRTIO_DEV_STATS_ENABLED)
> -			vq->stats.guest_notifications++;
> -		if (dev->notify_ops->guest_notified)
> -			dev->notify_ops->guest_notified(dev->vid);
> -	}
> +	if (kick)
> +		vhost_vring_inject_irq(dev, vq);
>  }
> 
>  static __rte_always_inline void
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index 6a9f32972a..2e4a9fdea4 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
> --
> 2.39.2