quoted

@@ -419,17 +446,52 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
 struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
-	struct vmpacket_descriptor *desc;
+	struct vmpacket_descriptor *desc, *desc_copy;
+	u32 bytes_avail, pkt_len, pkt_offset;

-	hv_debug_delay_test(channel, MESSAGE_DELAY);
-	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+	desc = hv_pkt_iter_first_raw(channel);
+	if (!desc)
 		return NULL;

-	desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
-	if (desc)
-		prefetch((char *)desc + (desc->len8 << 3));
+	bytes_avail = hv_pkt_iter_avail(rbi);
+
+	/*
+	 * Ensure the compiler does not use references to incoming Hyper-V values (which
+	 * could change at any moment) when reading local variables later in the code
+	 */
+	pkt_len = READ_ONCE(desc->len8) << 3;
+	pkt_offset = READ_ONCE(desc->offset8) << 3;
+
+	/*
+	 * If pkt_len is invalid, set it to the smaller of hv_pkt_iter_avail() and
+	 * rbi->pkt_buffer_size
+	 */
+	if (rbi->pkt_buffer_size < bytes_avail)
+		bytes_avail = rbi->pkt_buffer_size;

I think the above could be combined with the earlier call to hv_pkt_iter_avail(),
and more logically expressed as:

	bytes_avail = min(rbi->pkt_buffer_size, hv_pkt_iter_avail(rbi));


This is a minor nit.  Everything else in this patch looks good to me.

Thanks for the feedback, Michael; I'll send v3 to address it shortly.

  Andrea