@@ -437,6 +437,29 @@ static void gve_rx_skb_hash(struct sk_buff *skb,
skb_set_hash(skb, le32_to_cpu(compl_desc->hash), hash_type);
}
+/* Expand the hardware timestamp to the full 64 bits of width, and add it to the
+ * skb.
+ *
+ * This algorithm works by using the passed hardware timestamp to generate a
+ * diff relative to the last read of the nic clock. This diff can be positive or
+ * negative, as it is possible that we have read the clock more recently than
+ * the hardware has received this packet. To detect this, we use the high bit of
+ * the diff, and assume that the read is more recent if the high bit is set. In
+ * this case we invert the process.
+ *
+ * Note that this means if the time delta between packet reception and the last
+ * clock read is greater than ~2 seconds, this will provide invalid results.
+ */
+static void __maybe_unused gve_rx_skb_hwtstamp(struct gve_rx_ring *rx, u32 hwts)
+{
+ s64 last_read = rx->gve->last_sync_nic_counter;
+ struct sk_buff *skb = rx->ctx.skb_head;
+ u32 low = (u32)last_read;
+ s32 diff = hwts - low;
+
+ skb_hwtstamps(skb)->hwtstamp = ns_to_ktime(last_read + diff);
+}
+
static void gve_rx_free_skb(struct napi_struct *napi, struct gve_rx_ring *rx)
{
if (!rx->ctx.skb_head)