virtio: virtqueue_pop - VIRTIO_F_IN_ORDER support

Add VIRTIO_F_IN_ORDER feature support in virtqueue_split_pop and
virtqueue_packed_pop.

VirtQueueElements popped from the available/descritpor ring are added to
the VirtQueue's used_elems array in-order and in the same fashion as
they would be added the used and descriptor rings, respectively.

This will allow us to keep track of the current order, what elements
have been written, as well as an element's essential data after being
processed.

Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <20240710125522.4168043-3-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 583a22416333e98abb5926c3af7e43ad9f76a463..98eb601b0943000e9d60f6645f1107506fb14a72 100644 (file)
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1505,7 +1505,7 @@ static void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_nu
 
 static void *virtqueue_split_pop(VirtQueue *vq, size_t sz)
 {
-    unsigned int i, head, max;
+    unsigned int i, head, max, idx;
     VRingMemoryRegionCaches *caches;
     MemoryRegionCache indirect_desc_cache;
     MemoryRegionCache *desc_cache;
@@ -1629,6 +1629,13 @@ static void *virtqueue_split_pop(VirtQueue *vq, size_t sz)
         elem->in_sg[i] = iov[out_num + i];
     }
 
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_IN_ORDER)) {
+        idx = (vq->last_avail_idx - 1) % vq->vring.num;
+        vq->used_elems[idx].index = elem->index;
+        vq->used_elems[idx].len = elem->len;
+        vq->used_elems[idx].ndescs = elem->ndescs;
+    }
+
     vq->inuse++;
 
     trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
@@ -1762,6 +1769,13 @@ static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
 
     elem->index = id;
     elem->ndescs = (desc_cache == &indirect_desc_cache) ? 1 : elem_entries;
+
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_IN_ORDER)) {
+        vq->used_elems[vq->last_avail_idx].index = elem->index;
+        vq->used_elems[vq->last_avail_idx].len = elem->len;
+        vq->used_elems[vq->last_avail_idx].ndescs = elem->ndescs;
+    }
+
     vq->last_avail_idx += elem->ndescs;
     vq->inuse += elem->ndescs;