[RFC PATCH v8 08/21] vhost: Add SVQElement

["Eugenio Pérez" <eperezma@redhat.com>]

This allows SVQ to add metadata to the different queue elements.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |  8 ++++--
 hw/virtio/vhost-shadow-virtqueue.c | 46 ++++++++++++++++--------------
 2 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index 50f45153c0..e06ac52158 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -15,6 +15,10 @@
 #include "standard-headers/linux/vhost_types.h"
 #include "hw/virtio/vhost-iova-tree.h"
 
+typedef struct SVQElement {
+    VirtQueueElement elem;
+} SVQElement;
+
 typedef void (*VirtQueueElementCallback)(VirtIODevice *vdev,
                                          const VirtQueueElement *elem);
 
@@ -64,10 +68,10 @@ typedef struct VhostShadowVirtqueue {
     VhostIOVATree *iova_tree;
 
     /* Map for use the guest's descriptors */
-    VirtQueueElement **ring_id_maps;
+    SVQElement **ring_id_maps;
 
     /* Next VirtQueue element that guest made available */
-    VirtQueueElement *next_guest_avail_elem;
+    SVQElement *next_guest_avail_elem;
 
     /*
      * Backup next field for each descriptor so we can recover securely, not
diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 2d5d27d29c..044005ba89 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -171,9 +171,10 @@ static bool vhost_svq_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg,
     return true;
 }
 
-static bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
-                                VirtQueueElement *elem, unsigned *head)
+static bool vhost_svq_add_split(VhostShadowVirtqueue *svq, SVQElement *svq_elem,
+                                unsigned *head)
 {
+    const VirtQueueElement *elem = &svq_elem->elem;
     unsigned avail_idx;
     vring_avail_t *avail = svq->vring.avail;
     bool ok;
@@ -222,7 +223,7 @@ 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, SVQElement *elem)
 {
     unsigned qemu_head;
     bool ok = vhost_svq_add_split(svq, elem, &qemu_head);
@@ -272,19 +273,21 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
         virtio_queue_set_notification(svq->vq, false);
 
         while (true) {
+            SVQElement *svq_elem;
             VirtQueueElement *elem;
             bool ok;
 
             if (svq->next_guest_avail_elem) {
-                elem = g_steal_pointer(&svq->next_guest_avail_elem);
+                svq_elem = g_steal_pointer(&svq->next_guest_avail_elem);
             } else {
-                elem = virtqueue_pop(svq->vq, sizeof(*elem));
+                svq_elem = virtqueue_pop(svq->vq, sizeof(*svq_elem));
             }
 
-            if (!elem) {
+            if (!svq_elem) {
                 break;
             }
 
+            elem = &svq_elem->elem;
             if (elem->out_num + elem->in_num > vhost_svq_available_slots(svq)) {
                 /*
                  * This condition is possible since a contiguous buffer in GPA
@@ -297,11 +300,11 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
                  * queue the current guest descriptor and ignore further kicks
                  * until some elements are used.
                  */
-                svq->next_guest_avail_elem = elem;
+                svq->next_guest_avail_elem = svq_elem;
                 return;
             }
 
-            ok = vhost_svq_add(svq, elem);
+            ok = vhost_svq_add(svq, svq_elem);
             if (unlikely(!ok)) {
                 /* VQ is broken, just return and ignore any other kicks */
                 return;
@@ -368,8 +371,7 @@ static uint16_t vhost_svq_last_desc_of_chain(const VhostShadowVirtqueue *svq,
     return i;
 }
 
-static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
-                                           uint32_t *len)
+static SVQElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq, uint32_t *len)
 {
     const vring_used_t *used = svq->vring.used;
     vring_used_elem_t used_elem;
@@ -399,8 +401,8 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
         return NULL;
     }
 
-    num = svq->ring_id_maps[used_elem.id]->in_num +
-          svq->ring_id_maps[used_elem.id]->out_num;
+    num = svq->ring_id_maps[used_elem.id]->elem.in_num +
+          svq->ring_id_maps[used_elem.id]->elem.out_num;
     last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
     svq->desc_next[last_used_chain] = svq->free_head;
     svq->free_head = used_elem.id;
@@ -421,11 +423,13 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
         vhost_svq_disable_notification(svq);
         while (true) {
             uint32_t len;
-            g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq, &len);
-            if (!elem) {
+            g_autofree SVQElement *svq_elem = vhost_svq_get_buf(svq, &len);
+            VirtQueueElement *elem;
+            if (!svq_elem) {
                 break;
             }
 
+            elem = &svq_elem->elem;
             if (svq->ops && svq->ops->used_elem_handler) {
                 svq->ops->used_elem_handler(svq->vdev, elem);
             }
@@ -580,7 +584,7 @@ void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
     memset(svq->vring.desc, 0, driver_size);
     svq->vring.used = qemu_memalign(qemu_real_host_page_size(), device_size);
     memset(svq->vring.used, 0, device_size);
-    svq->ring_id_maps = g_new0(VirtQueueElement *, svq->vring.num);
+    svq->ring_id_maps = g_new0(SVQElement *, svq->vring.num);
     svq->desc_next = g_new0(uint16_t, svq->vring.num);
     for (unsigned i = 0; i < svq->vring.num - 1; i++) {
         svq->desc_next[i] = cpu_to_le16(i + 1);
@@ -594,7 +598,7 @@ void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
 void vhost_svq_stop(VhostShadowVirtqueue *svq)
 {
     event_notifier_set_handler(&svq->svq_kick, NULL);
-    g_autofree VirtQueueElement *next_avail_elem = NULL;
+    g_autofree SVQElement *next_avail_elem = NULL;
 
     if (!svq->vq) {
         return;
@@ -604,16 +608,16 @@ void vhost_svq_stop(VhostShadowVirtqueue *svq)
     vhost_svq_flush(svq, false);
 
     for (unsigned i = 0; i < svq->vring.num; ++i) {
-        g_autofree VirtQueueElement *elem = NULL;
-        elem = g_steal_pointer(&svq->ring_id_maps[i]);
-        if (elem) {
-            virtqueue_detach_element(svq->vq, elem, 0);
+        g_autofree SVQElement *svq_elem = NULL;
+        svq_elem = g_steal_pointer(&svq->ring_id_maps[i]);
+        if (svq_elem) {
+            virtqueue_detach_element(svq->vq, &svq_elem->elem, 0);
         }
     }
 
     next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
     if (next_avail_elem) {
-        virtqueue_detach_element(svq->vq, next_avail_elem, 0);
+        virtqueue_detach_element(svq->vq, &next_avail_elem->elem, 0);
     }
     svq->vq = NULL;
     g_free(svq->desc_next);
-- 
2.27.0