sims/nic/i40e_bm: add support for 16b rx descriptors

The newer linux drivers now use 16b instead of 32b descriptors. So far
this leads to an abort. This adds proper support for 16b descriptors.

sims/nic/i40e_bm/i40e_bm.h

@@ -133,6 +133,7 @@ class queue_base {
     enum state state;
     uint32_t index;
     void *desc;
+    size_t desc_len;
     void *data;
     size_t data_len;
     size_t data_capacity;

sims/nic/i40e_bm/i40e_lan.cc

@@ -287,12 +287,6 @@ void lan_queue_rx::initialize() {
   crc_strip = !!(((*hbsz_p) >> 13) & 0x1);
   rxmax = (((*rxmax_p) >> 6) & ((1 << 14) - 1)) * 128;
 
-  if (!longdesc) {
-    log << "lan_queue_rx::initialize: currently only 32B descs "
-           " supported"
-        << logger::endl;
-    abort();
-  }
   if (dtype != 0) {
     log << "lan_queue_rx::initialize: no header split supported"
         << logger::endl;
@@ -359,12 +353,17 @@ void lan_queue_rx::rx_desc_ctx::process() {
 
 void lan_queue_rx::rx_desc_ctx::packet_received(const void *data, size_t pktlen,
                                                 bool last) {
-  union i40e_32byte_rx_desc *rxd =
-      reinterpret_cast<union i40e_32byte_rx_desc *>(desc);
+  // we only use fields in the lowest 16b anyways, even if set to 32b
+  union i40e_16byte_rx_desc *rxd =
+      reinterpret_cast<union i40e_16byte_rx_desc *>(desc);
 
   uint64_t addr = rxd->read.pkt_addr;
 
   memset(rxd, 0, sizeof(*rxd));
+  // for 32b descriptors need to ensure to zero later fields
+  if (desc_len > sizeof(*rxd))
+    memset((uint8_t *)desc + sizeof(*rxd), 0, desc_len - sizeof(*rxd));
+
   rxd->wb.qword1.status_error_len |= (1 << I40E_RX_DESC_STATUS_DD_SHIFT);
   rxd->wb.qword1.status_error_len |= (pktlen << I40E_RXD_QW1_LENGTH_PBUF_SHIFT);
 

sims/nic/i40e_bm/i40e_queues.cc

@@ -276,10 +276,11 @@ queue_base::desc_ctx::desc_ctx(queue_base &queue_)
     : queue(queue_),
       state(DESC_EMPTY),
       index(0),
+      desc_len(queue_.desc_len),
       data(nullptr),
       data_len(0),
       data_capacity(0) {
-  desc = new uint8_t[queue_.desc_len];
+  desc = new uint8_t[desc_len];
 }
 
 queue_base::desc_ctx::~desc_ctx() {