dev: add support for multi gem5 runs

Multi gem5 is an extension to gem5 to enable parallel simulation of a
distributed system (e.g. simulation of a pool of machines
connected by Ethernet links). A multi gem5 run consists of seperate gem5
processes running in parallel (potentially on different hosts/slots on
a cluster). Each gem5 process executes the simulation of a component of the
simulated distributed system (e.g. a multi-core board with an Ethernet NIC).

The patch implements the "distributed" Ethernet link device
(dev/src/multi_etherlink.[hh.cc]). This device will send/receive
(simulated) Ethernet packets to/from peer gem5 processes. The interface
to talk to the peer gem5 processes is defined in dev/src/multi_iface.hh and
in tcp_iface.hh.

There is also a central message server process (util/multi/tcp_server.[hh,cc])
which acts like an Ethernet switch and transfers messages among the gem5 peers.

A multi gem5 simulations can be kicked off by the util/multi/gem5-multi.sh
wrapper script.

Checkpoints are supported by multi-gem5. The checkpoint must be
initiated by a single gem5 process. E.g., the gem5 process with rank 0
can take a checkpoint from the bootscript just before it invokes
'mpirun' to launch an MPI test. The message server process will notify
all the other peer gem5 processes and make them take a checkpoint, too
(after completing a global synchronisation to ensure that there are no
inflight messages among gem5).

1 files changed, 18 insertions, 0 deletions

diff --git a/src/dev/etherpkt.cc b/src/dev/etherpkt.cc
index 548a1f179..58b53b5e6 100644
--- a/src/dev/etherpkt.cc
+++ b/src/dev/etherpkt.cc
@@ -31,6 +31,7 @@
 #include <iostream>
 
 #include "base/misc.hh"
+#include "base/inet.hh"
 #include "dev/etherpkt.hh"
 #include "sim/serialize.hh"
 
@@ -50,3 +51,20 @@ EthPacketData::unserialize(const string &base, CheckpointIn &cp)
     if (length)
         arrayParamIn(cp, base + ".data", data, length);
 }
+
+void
+EthPacketData::packAddress(uint8_t *src_addr,
+                           uint8_t *dst_addr,
+                           unsigned &nbytes)
+{
+    Net::EthHdr *hdr = (Net::EthHdr *)data;
+    assert(hdr->src().size() == hdr->dst().size());
+    if (nbytes < hdr->src().size())
+        panic("EthPacketData::packAddress() Buffer overflow");
+
+    memcpy(dst_addr, hdr->dst().bytes(), hdr->dst().size());
+    memcpy(src_addr, hdr->src().bytes(), hdr->src().size());
+
+    nbytes = hdr->src().size();
+}
+