Re: [PATCH v5 14/15] vhost: add notification for packed ring

[Tiwei Bie <tiwei.bie@intel.com>]

On Fri, Jun 22, 2018 at 03:43:26PM +0200, Maxime Coquelin wrote:
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/vhost.c         | 55 +++++++++++++++++++++++++++----
>  lib/librte_vhost/vhost.h         | 71 ++++++++++++++++++++++++++++++++++++----
>  lib/librte_vhost/vhost_user.c    | 29 +++++++++++++---
>  lib/librte_vhost/virtio-packed.h | 11 +++++++
>  lib/librte_vhost/virtio_net.c    | 12 +++----
>  5 files changed, 154 insertions(+), 24 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> index 7cbf1eded..c26162542 100644
> --- a/lib/librte_vhost/vhost.c
> +++ b/lib/librte_vhost/vhost.c
> @@ -595,7 +595,11 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
>  	if (!vq)
>  		return -1;
>  
> -	vhost_vring_call(dev, vq);
> +	if (vq_is_packed(dev))
> +		vhost_vring_call_packed(dev, vq);
> +	else
> +		vhost_vring_call_split(dev, vq);
> +
>  	return 0;
>  }
>  
> @@ -616,20 +620,59 @@ rte_vhost_avail_entries(int vid, uint16_t queue_id)
>  	return *(volatile uint16_t *)&vq->avail->idx - vq->last_used_idx;
>  }
>  
> +static inline int
> +vhost_enable_notify_split(struct vhost_virtqueue *vq, int enable)
> +{
> +	if (enable)
> +		vq->used->flags &= ~VRING_USED_F_NO_NOTIFY;
> +	else
> +		vq->used->flags |= VRING_USED_F_NO_NOTIFY;
> +
> +	return 0;
> +}
> +
> +static inline int
> +vhost_enable_notify_packed(struct virtio_net *dev,
> +		struct vhost_virtqueue *vq, int enable)
> +{
> +	uint16_t flags;
> +
> +	if (!enable) {
> +		vq->device_event->desc_event_flags = RING_EVENT_FLAGS_DISABLE;
> +		return 0;
> +	}
> +
> +	flags = RING_EVENT_FLAGS_DISABLE;

Should be RING_EVENT_FLAGS_ENABLE.

> +	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> +		flags = RING_EVENT_FLAGS_DESC;
> +		vq->device_event->desc_event_off_wrap = vq->last_avail_idx |
> +			vq->avail_wrap_counter << 15;
> +	}
> +
> +	rte_smp_wmb();
> +
> +	vq->device_event->desc_event_flags = flags;
> +
> +	rte_smp_wmb();
> +
> +	return 0;
> +}
> +
>  int
>  rte_vhost_enable_guest_notification(int vid, uint16_t queue_id, int enable)
>  {
>  	struct virtio_net *dev = get_device(vid);
> +	struct vhost_virtqueue *vq;
>  
>  	if (!dev)
>  		return -1;
>  
> -	if (enable)
> -		dev->virtqueue[queue_id]->used->flags &=
> -			~VRING_USED_F_NO_NOTIFY;
> +	vq = dev->virtqueue[queue_id];
> +
> +	if (vq_is_packed(dev))
> +		return vhost_enable_notify_packed(dev, vq, enable);
>  	else
> -		dev->virtqueue[queue_id]->used->flags |= VRING_USED_F_NO_NOTIFY;
> -	return 0;
> +		return vhost_enable_notify_split(vq, enable);
>  }
>  
>  void
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 5dcb61c71..99db688a8 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -21,6 +21,7 @@
>  
>  #include "rte_vhost.h"
>  #include "rte_vdpa.h"
> +#include "virtio-packed.h"

The definitions in virtio-packed.h probably will conflit
with the definitions in linux/virtio_ring.h which is
included by linux/vhost.h (which is also included by
this file) when packed ring is upstreamed to linux.
It probably will cause build issues in the future.

>  
>  /* Used to indicate that the device is running on a data core */
>  #define VIRTIO_DEV_RUNNING 1
> @@ -95,8 +96,14 @@ struct vhost_virtqueue {
>  		struct vring_desc	*desc;
>  		struct vring_desc_packed   *desc_packed;
>  	};
> -	struct vring_avail	*avail;
> -	struct vring_used	*used;
> +	union {
> +		struct vring_avail	*avail;
> +		struct vring_packed_desc_event *driver_event;
> +	};
> +	union {
> +		struct vring_used	*used;
> +		struct vring_packed_desc_event *device_event;
> +	};
>  	uint32_t		size;
>  
>  	uint16_t		last_avail_idx;
> @@ -614,7 +621,7 @@ vhost_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
>  }
>  
>  static __rte_always_inline void
> -vhost_vring_call(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  {
>  	/* Flush used->idx update before we read avail->flags. */
>  	rte_mb();
> @@ -625,11 +632,11 @@ vhost_vring_call(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  		uint16_t new = vq->last_used_idx;
>  
>  		VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
> -			__func__,
> -			vhost_used_event(vq),
> -			old, new);
> +				__func__,
> +				vhost_used_event(vq),
> +				old, new);
>  		if (vhost_need_event(vhost_used_event(vq), new, old)
> -			&& (vq->callfd >= 0)) {
> +				&& (vq->callfd >= 0)) {
>  			vq->signalled_used = vq->last_used_idx;
>  			eventfd_write(vq->callfd, (eventfd_t) 1);
>  		}
> @@ -641,4 +648,54 @@ vhost_vring_call(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  	}
>  }
>  
> +static __rte_always_inline void
> +vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +{
> +	uint16_t old, new, off, off_wrap, wrap;
> +	bool kick = false;
> +
> +

There is no need to have two blank lines.

> +	/*  Flush used desc update. */
> +	rte_smp_mb();
> +
> +	if (!(dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))) {
> +		if (vq->driver_event->desc_event_flags !=
> +				RING_EVENT_FLAGS_DISABLE)
> +			kick = true;
> +		goto kick;
> +	}
> +
> +	old = vq->signalled_used;
> +	new = vq->last_used_idx;
> +	vq->signalled_used = new;
> +
> +	if (vq->driver_event->desc_event_flags != RING_EVENT_FLAGS_DESC) {
> +		if (vq->driver_event->desc_event_flags !=
> +				RING_EVENT_FLAGS_DISABLE)
> +			kick = true;
> +		goto kick;
> +	}
> +
> +	rte_smp_rmb();
> +
> +	off_wrap = vq->driver_event->desc_event_off_wrap;
> +	off = off_wrap & ~(1 << 15);
> +	wrap = vq->used_wrap_counter;
> +
> +	if (new < old) {
> +		new += vq->size;
> +		wrap ^= 1;
> +	}
> +
> +	if (wrap != off_wrap >> 15)
> +		off += vq->size;
> +
> +	if (vhost_need_event(off, new, old))
> +		kick = true;
> +
> +kick:
> +	if (kick)
> +		eventfd_write(vq->callfd, (eventfd_t)1);
> +}
> +
>  #endif /* _VHOST_NET_CDEV_H_ */
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index a08d99314..c74924564 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -509,9 +509,6 @@ translate_ring_addresses(struct virtio_net *dev, int vq_index)
>  		len = sizeof(struct vring_desc_packed) * vq->size;
>  		vq->desc_packed = (struct vring_desc_packed *) ring_addr_to_vva
>  			(dev, vq, addr->desc_user_addr, &len);
> -		vq->desc = NULL;
> -		vq->avail = NULL;
> -		vq->used = NULL;

There is no need to add them from the beginning.

>  		vq->log_guest_addr = 0;
>  		if (vq->desc_packed == 0 ||
>  				len != sizeof(struct vring_desc_packed) *
> @@ -526,6 +523,30 @@ translate_ring_addresses(struct virtio_net *dev, int vq_index)
>  		vq = dev->virtqueue[vq_index];
>  		addr = &vq->ring_addrs;
>  
> +		len = sizeof(struct vring_packed_desc_event);
> +		vq->driver_event = (struct vring_packed_desc_event *)
> +					(uintptr_t)ring_addr_to_vva(dev,
> +					vq, addr->avail_user_addr, &len);
> +		if (vq->driver_event == 0 ||

It's better to compare with NULL.

> +				len != sizeof(struct vring_packed_desc_event)) {
> +			RTE_LOG(DEBUG, VHOST_CONFIG,
> +				"(%d) failed to find driver area address.\n",
> +				dev->vid);
> +			return dev;
> +		}
> +
> +		len = sizeof(struct vring_packed_desc_event);
> +		vq->device_event = (struct vring_packed_desc_event *)
> +					(uintptr_t)ring_addr_to_vva(dev,
> +					vq, addr->used_user_addr, &len);
> +		if (vq->device_event == 0 ||

It's better to compare with NULL.

> +				len != sizeof(struct vring_packed_desc_event)) {
> +			RTE_LOG(DEBUG, VHOST_CONFIG,
> +				"(%d) failed to find device area address.\n",
> +				dev->vid);
> +			return dev;
> +		}
> +
>  		return dev;
>  	}
>  
> @@ -542,8 +563,6 @@ translate_ring_addresses(struct virtio_net *dev, int vq_index)
>  			dev->vid);
>  		return dev;
>  	}
> -	vq->desc_packed = NULL;

There is no need to add it from the beginning.

Best regards,
Tiwei Bie