vhost-vdpa: change name and polarity for vhost_vdpa_one_time_request()

The name vhost_vdpa_one_time_request() was confusing. No
matter whatever it returns, its typical occurrence had
always been at requests that only need to be applied once.
And the name didn't suggest what it actually checks for.
Change it to vhost_vdpa_first_dev() with polarity flipped
for better readibility of code. That way it is able to
reflect what the check is really about.

This call is applicable to request which performs operation
only once, before queues are set up, and usually at the beginning
of the caller function. Document the requirement for it in place.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Message-Id: <1651890498-24478-7-git-send-email-si-wei.liu@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

hw/virtio/vhost-vdpa.c

@@ -368,11 +368,18 @@ static void vhost_vdpa_get_iova_range(struct vhost_vdpa *v)
                                     v->iova_range.last);
 }
 
-static bool vhost_vdpa_one_time_request(struct vhost_dev *dev)
+/*
+ * The use of this function is for requests that only need to be
+ * applied once. Typically such request occurs at the beginning
+ * of operation, and before setting up queues. It should not be
+ * used for request that performs operation until all queues are
+ * set, which would need to check dev->vq_index_end instead.
+ */
+static bool vhost_vdpa_first_dev(struct vhost_dev *dev)
 {
     struct vhost_vdpa *v = dev->opaque;
 
-    return v->index != 0;
+    return v->index == 0;
 }
 
 static int vhost_vdpa_get_dev_features(struct vhost_dev *dev,
@@ -453,7 +460,7 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
 
     vhost_vdpa_get_iova_range(v);
 
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_first_dev(dev)) {
         return 0;
     }
 
@@ -596,7 +603,7 @@ static int vhost_vdpa_memslots_limit(struct vhost_dev *dev)
 static int vhost_vdpa_set_mem_table(struct vhost_dev *dev,
                                     struct vhost_memory *mem)
 {
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_first_dev(dev)) {
         return 0;
     }
 
@@ -625,7 +632,7 @@ static int vhost_vdpa_set_features(struct vhost_dev *dev,
     struct vhost_vdpa *v = dev->opaque;
     int ret;
 
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_first_dev(dev)) {
         return 0;
     }
 
@@ -667,7 +674,7 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
 
     features &= f;
 
-    if (!vhost_vdpa_one_time_request(dev)) {
+    if (vhost_vdpa_first_dev(dev)) {
         r = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, &features);
         if (r) {
             return -EFAULT;
@@ -1120,7 +1127,7 @@ static int vhost_vdpa_set_log_base(struct vhost_dev *dev, uint64_t base,
                                      struct vhost_log *log)
 {
     struct vhost_vdpa *v = dev->opaque;
-    if (v->shadow_vqs_enabled || vhost_vdpa_one_time_request(dev)) {
+    if (v->shadow_vqs_enabled || !vhost_vdpa_first_dev(dev)) {
         return 0;
     }
 
@@ -1242,7 +1249,7 @@ static int vhost_vdpa_get_features(struct vhost_dev *dev,
 
 static int vhost_vdpa_set_owner(struct vhost_dev *dev)
 {
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_first_dev(dev)) {
         return 0;
     }