[RFC PATCH v9 08/23] vhost: Decouple vhost_svq_add_split from VirtQueueElement

[Eugenio Pérez]

VirtQueueElement comes from the guest, but we're heading SVQ to be able
to inject element without the guest's knowledge.

To do so, make this accept sg buffers directly, instead of using
VirtQueueElement.

Add vhost_svq_add_element to maintain element convenience

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.c | 38 +++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index 2fc5789b73..46d3c1d74f 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -172,30 +172,32 @@ static bool 
vhost_svq_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg,
 }
 
 static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
-                                VirtQueueElement *elem, unsigned *head)
+                                const struct iovec *out_sg, size_t out_num,
+                                const struct iovec *in_sg, size_t in_num,
+                                unsigned *head)
 {
     unsigned avail_idx;
     vring_avail_t *avail = svq->vring.avail;
     bool ok;
-    g_autofree hwaddr *sgs = g_new(hwaddr, MAX(elem->out_num, elem->in_num));
+    g_autofree hwaddr *sgs = NULL;
 
     *head = svq->free_head;
 
     /* We need some descriptors here */
-    if (unlikely(!elem->out_num && !elem->in_num)) {
+    if (unlikely(!out_num && !in_num)) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "Guest provided element with no descriptors");
         return false;
     }
 
-    ok = vhost_svq_vring_write_descs(svq, sgs, elem->out_sg, elem->out_num,
-                                     elem->in_num > 0, false);
+    sgs = g_new(hwaddr, MAX(out_num, in_num));
+    ok = vhost_svq_vring_write_descs(svq, sgs, out_sg, out_num, in_num > 0,
+                                     false);
     if (unlikely(!ok)) {
         return false;
     }
 
-    ok = vhost_svq_vring_write_descs(svq, sgs, elem->in_sg, elem->in_num, 
false,
-                                     true);
+    ok = vhost_svq_vring_write_descs(svq, sgs, in_sg, in_num, false, true);
     if (unlikely(!ok)) {
         /* TODO unwind out_sg */
         return false;
@@ -223,10 +225,13 @@ static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
  * takes ownership of the element: In case of failure, it is free and the SVQ
  * is considered broken.
  */
-static bool vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
+static bool vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec 
*out_sg,
+                          size_t out_num, const struct iovec *in_sg,
+                          size_t in_num, VirtQueueElement *elem)
 {
     unsigned qemu_head;
-    bool ok = vhost_svq_add_split(svq, elem, &qemu_head);
+    bool ok = vhost_svq_add_split(svq, out_sg, out_num, in_sg, in_num,
+                                  &qemu_head);
     if (unlikely(!ok)) {
         g_free(elem);
         return false;
@@ -250,6 +255,18 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)
     event_notifier_set(&svq->hdev_kick);
 }
 
+static bool vhost_svq_add_element(VhostShadowVirtqueue *svq,
+                                  VirtQueueElement *elem)
+{
+    bool ok = vhost_svq_add(svq, elem->out_sg, elem->out_num, elem->in_sg,
+                            elem->in_num, elem);
+    if (ok) {
+        vhost_svq_kick(svq);
+    }
+
+    return ok;
+}
+
 /**
  * Forward available buffers.
  *
@@ -302,12 +319,11 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue 
*svq)
                 return;
             }
 
-            ok = vhost_svq_add(svq, elem);
+            ok = vhost_svq_add_element(svq, g_steal_pointer(&elem));
             if (unlikely(!ok)) {
                 /* VQ is broken, just return and ignore any other kicks */
                 return;
             }
-            vhost_svq_kick(svq);
         }
 
         virtio_queue_set_notification(svq->vq, true);
-- 
2.31.1