[RFC PATCH v9 13/23] vhost: Add vhost_svq_inject

[Eugenio Pérez]

This allows qemu to inject buffers to the device.

Signed-off-by: Eugenio Pérez <epere...@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |  2 ++
 hw/virtio/vhost-shadow-virtqueue.c | 34 ++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
b/hw/virtio/vhost-shadow-virtqueue.h
index a811f90e01..d01d2370db 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -98,6 +98,8 @@ bool vhost_svq_valid_features(uint64_t features, Error 
**errp);
 
 void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
                          const VirtQueueElement *elem, uint32_t len);
+int vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
+                     size_t out_num, size_t in_num, void *opaque);
 void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
 void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd);
 void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index 492bb12b5f..bd9e34b413 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -283,6 +283,40 @@ static bool vhost_svq_add_element(VhostShadowVirtqueue 
*svq,
     return ok;
 }
 
+/**
+ * Inject a chain of buffers to the device
+ *
+ * @svq: Shadow VirtQueue
+ * @iov: I/O vector
+ * @out_num: Number of front out descriptors
+ * @in_num: Number of last input descriptors
+ * @opaque: Contextual data to store in descriptor
+ *
+ * Return 0 on success, -ENOMEM if cannot inject
+ */
+int vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
+                     size_t out_num, size_t in_num, void *opaque)
+{
+    bool ok;
+
+    /*
+     * All vhost_svq_inject calls are controlled by qemu so we won't hit this
+     * assertions.
+     */
+    assert(out_num || in_num);
+    assert(svq->ops);
+
+    if (unlikely(svq->next_guest_avail_elem)) {
+        error_report("Injecting in a full queue");
+        return -ENOMEM;
+    }
+
+    ok = vhost_svq_add(svq, iov, out_num, iov + out_num, in_num, opaque);
+    assert(ok);
+    vhost_svq_kick(svq);
+    return 0;
+}
+
 /**
  * Forward available buffers.
  *
-- 
2.31.1