This combines the previous two feature functions, forwarding the guest
ones to the device and setting the transport ones that the SVQ supports
with the device.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |  3 +++
 hw/virtio/vhost-shadow-virtqueue.c | 31 ++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index 1aae6a2297..af8f8264c0 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -17,6 +17,9 @@ typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
 
 bool vhost_svq_valid_device_features(uint64_t *features);
 bool vhost_svq_valid_guest_features(uint64_t *features);
+bool vhost_svq_ack_guest_features(uint64_t dev_features,
+                                  uint64_t guest_features,
+                                  uint64_t *acked_features);
 
 void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
 void vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int call_fd);
diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index f70160d7ca..a6fb7e3c8f 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -113,6 +113,37 @@ bool vhost_svq_valid_guest_features(uint64_t *guest_features)
     return !(guest_transport_features & (transport ^ valid));
 }
 
+/**
+ * VirtIO features that SVQ must acknowledge to device.
+ *
+ * It combines the SVQ transport compatible features with the guest's device
+ * features.
+ *
+ * @dev_features    The device offered features
+ * @guest_features  The guest acknowledge features
+ * @acked_features  The guest acknowledge features in the device side plus SVQ
+ *                  transport ones.
+ *
+ * Returns true if SVQ can work with this features, false otherwise
+ */
+bool vhost_svq_ack_guest_features(uint64_t dev_features,
+                                  uint64_t guest_features,
+                                  uint64_t *acked_features)
+{
+    static const uint64_t transport = MAKE_64BIT_MASK(VIRTIO_TRANSPORT_F_START,
+                            VIRTIO_TRANSPORT_F_END - VIRTIO_TRANSPORT_F_START);
+
+    bool ok = vhost_svq_valid_device_features(&dev_features) &&
+              vhost_svq_valid_guest_features(&guest_features);
+    if (unlikely(!ok)) {
+        return false;
+    }
+
+    *acked_features = (dev_features & transport) |
+                      (guest_features & ~transport);
+    return true;
+}
+
 /* Forward guest notifications */
 static void vhost_handle_guest_kick(EventNotifier *n)
 {
-- 
2.27.0