lkl: Refactor net_enqueue

This commit introduces some more descriptive names to the two queues
used by virtio_net, and wraps up some of the conditionals in net_enqueue
into functions so that it's a little more intention-revealing. As a
result, it's forced to pull the virtqueue struct definition into
virtio.h, but exposing more info is justified by keeping the virtio
structs closer together and allowing clearer code in virtio_net.

Signed-off-by: Patrick Collins <pscollins@google.com>

tools/lkl/lib/virtio.c

@@ -46,18 +46,6 @@
 #define bad_driver(msg) do { } while (0)
 #endif /* DEBUG */
 
-struct virtio_queue {
- uint32_t num_max;
- uint32_t num;
- uint32_t ready;
-
- struct lkl_vring_desc *desc;
- struct lkl_vring_avail *avail;
- struct lkl_vring_used *used;
- uint16_t last_avail_idx;
-};
-
-
 static inline uint16_t virtio_get_used_event(struct virtio_queue *q)
 {
  return q->avail->ring[q->num];

tools/lkl/lib/virtio.h

@@ -25,6 +25,17 @@ struct virtio_dev_ops {
  int (*enqueue)(struct virtio_dev *dev, struct virtio_req *req);
 };
 
+struct virtio_queue {
+ uint32_t num_max;
+ uint32_t num;
+ uint32_t ready;
+
+ struct lkl_vring_desc *desc;
+ struct lkl_vring_avail *avail;
+ struct lkl_vring_used *used;
+ uint16_t last_avail_idx;
+};
+
 struct virtio_dev {
  uint32_t device_id;
  uint32_t vendor_id;

tools/lkl/lib/virtio_net.c

@@ -7,6 +7,21 @@
 
 #define BIT(x) (1ULL << x)
 
+/* We always have 2 queues on a netdev: one for tx, one for rx. */
+#define RX_QUEUE_IDX 0
+#define TX_QUEUE_IDX 1
+#define NUM_QUEUES (TX_QUEUE_IDX + 1)
+
+#ifdef DEBUG
+#define bad_request(s) do { \
+ lkl_printf("%s\n", s); \
+ panic(); \
+ } while (0)
+#else
+#define bad_request(s) lkl_printf("virtio_net: %s\n", s);
+#endif /* DEBUG */
+
+
 struct virtio_net_poll {
  struct virtio_net_dev *dev;
  struct lkl_sem_t *sem;
@@ -29,40 +44,54 @@ static int net_check_features(struct virtio_dev *dev)
  return -LKL_EINVAL;
 }
 
+static inline int is_rx_queue(struct virtio_dev *dev, struct virtio_queue *queue)
+{
+ return &dev->queue[RX_QUEUE_IDX] == queue;
+}
+
+static inline int is_tx_queue(struct virtio_dev *dev, struct virtio_queue *queue)
+{
+ return &dev->queue[TX_QUEUE_IDX] == queue;
+}
+
 static int net_enqueue(struct virtio_dev *dev, struct virtio_req *req)
 {
- struct lkl_virtio_net_hdr_v1 *h;
+ struct lkl_virtio_net_hdr_v1 *header;
  struct virtio_net_dev *net_dev;
  int ret, len;
  void *buf;
 
- h = req->buf[0].addr;
+ header = req->buf[0].addr;
  net_dev = container_of(dev, struct virtio_net_dev, dev);
- len = req->buf[0].len - sizeof(*h);
+ len = req->buf[0].len - sizeof(*header);
 
- buf = &h[1];
+ buf = &header[1];
 
  if (!len && req->buf_count > 1) {
  buf = req->buf[1].addr;
  len = req->buf[1].len;
  }
 
- if (req->q != dev->queue) {
+ /* Pick which virtqueue to send the buffer(s) to */
+ if (is_tx_queue(dev, req->q)) {
  ret = net_dev->ops->tx(net_dev->nd, buf, len);
  if (ret < 0) {
  lkl_host_ops.sem_up(net_dev->tx_poll.sem);
  return -1;
  }
- } else {
- h->num_buffers = 1;
+ } else if (is_rx_queue(dev, req->q)) {
+ header->num_buffers = 1;
  ret = net_dev->ops->rx(net_dev->nd, buf, &len);
  if (ret < 0) {
  lkl_host_ops.sem_up(net_dev->rx_poll.sem);
  return -1;
  }
+ } else {
+ bad_request("tried to push on non-existent queue");
+ return -1;
  }
 
- virtio_req_complete(req, len + sizeof(*h));
+ virtio_req_complete(req, len + sizeof(*header));
  return 0;
 }