vhost: introduce vring call API

Users of librte_vhost currently implement the vring call operation
themselves.  Each caller performs the operation slightly differently.

This patch introduces a new librte_vhost API called
rte_vhost_vring_call() that performs the operation so that vhost-user
applications don't have to duplicate it.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>

diff --git a/examples/vhost/virtio_net.c b/examples/vhost/virtio_net.c
index 496763d..f6e0067 100644 (file)
--- a/examples/vhost/virtio_net.c
+++ b/examples/vhost/virtio_net.c
@@ -178,13 +178,8 @@ vs_enqueue_pkts(struct vhost_dev *dev, uint16_t queue_id,
        *(volatile uint16_t *)&vr->used->idx += count;
        queue->last_used_idx += count;
 
-       /* flush used->idx update before we read avail->flags. */
-       rte_mb();
+       rte_vhost_vring_call(dev->vid, queue_id);
 
-       /* Kick the guest if necessary. */
-       if (!(vr->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-                       && (vr->callfd >= 0))
-               eventfd_write(vr->callfd, (eventfd_t)1);
        return count;
 }
 
@@ -367,9 +362,7 @@ vs_dequeue_pkts(struct vhost_dev *dev, uint16_t queue_id,
 
        vr->used->idx += i;
 
-       if (!(vr->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-                       && (vr->callfd >= 0))
-               eventfd_write(vr->callfd, (eventfd_t)1);
+       rte_vhost_vring_call(dev->vid, queue_id);
 
        return i;
 }

diff --git a/examples/vhost_scsi/vhost_scsi.c b/examples/vhost_scsi/vhost_scsi.c
index 38f5d82..da01ad3 100644 (file)
--- a/examples/vhost_scsi/vhost_scsi.c
+++ b/examples/vhost_scsi/vhost_scsi.c
@@ -81,7 +81,7 @@ descriptor_is_wr(struct vring_desc *cur_desc)
 }
 
 static void
-submit_completion(struct vhost_scsi_task *task)
+submit_completion(struct vhost_scsi_task *task, uint32_t q_idx)
 {
        struct rte_vhost_vring *vq;
        struct vring_used *used;
@@ -102,7 +102,7 @@ submit_completion(struct vhost_scsi_task *task)
        /* Send an interrupt back to the guest VM so that it knows
         * a completion is ready to be processed.
         */
-       eventfd_write(vq->callfd, (eventfd_t)1);
+       rte_vhost_vring_call(task->bdev->vid, q_idx);
 }
 
 static void
@@ -234,7 +234,7 @@ process_requestq(struct vhost_scsi_ctrlr *ctrlr, uint32_t q_idx)
                        task->resp->status = 0;
                        task->resp->resid = 0;
                }
-               submit_completion(task);
+               submit_completion(task, q_idx);
                rte_free(task);
        }
 }

diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
index 1a84ddf..d332069 100644 (file)
--- a/lib/librte_vhost/rte_vhost.h
+++ b/lib/librte_vhost/rte_vhost.h
@@ -57,7 +57,9 @@ struct rte_vhost_vring {
        struct vring_used       *used;
        uint64_t                log_guest_addr;
 
+       /** Deprecated, use rte_vhost_vring_call() instead. */
        int                     callfd;
+
        int                     kickfd;
        uint16_t                size;
 };
@@ -407,6 +409,19 @@ int rte_vhost_get_mem_table(int vid, struct rte_vhost_memory **mem);
 int rte_vhost_get_vhost_vring(int vid, uint16_t vring_idx,
                              struct rte_vhost_vring *vring);
 
+/**
+ * Notify the guest that used descriptors have been added to the vring.  This
+ * function acts as a memory barrier.
+ *
+ * @param vid
+ *  vhost device ID
+ * @param vring_idx
+ *  vring index
+ * @return
+ *  0 on success, -1 on failure
+ */
+int rte_vhost_vring_call(int vid, uint16_t vring_idx);
+
 /**
  * Get vhost RX queue avail count.
  *

diff --git a/lib/librte_vhost/rte_vhost_version.map b/lib/librte_vhost/rte_vhost_version.map
index 1e70495..df01031 100644 (file)
--- a/lib/librte_vhost/rte_vhost_version.map
+++ b/lib/librte_vhost/rte_vhost_version.map
@@ -52,3 +52,10 @@ DPDK_17.08 {
        rte_vhost_rx_queue_count;
 
 } DPDK_17.05;
+
+DPDK_18.02 {
+       global:
+
+       rte_vhost_vring_call;
+
+} DPDK_17.08;

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index a93c70d..4eb450c 100644 (file)
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -490,6 +490,27 @@ rte_vhost_get_vhost_vring(int vid, uint16_t vring_idx,
        return 0;
 }
 
+int
+rte_vhost_vring_call(int vid, uint16_t vring_idx)
+{
+       struct virtio_net *dev;
+       struct vhost_virtqueue *vq;
+
+       dev = get_device(vid);
+       if (!dev)
+               return -1;
+
+       if (vring_idx >= VHOST_MAX_VRING)
+               return -1;
+
+       vq = dev->virtqueue[vring_idx];
+       if (!vq)
+               return -1;
+
+       vhost_vring_call(vq);
+       return 0;
+}
+
 uint16_t
 rte_vhost_avail_entries(int vid, uint16_t queue_id)
 {