From 57a4bdd563db4bc12ad1aa3aaa6d0000cc486fc7 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 4 Feb 2019 14:39:33 +0200
Subject: Use QMP (QEMU Machine Protocol) events as machine log file

---
 bbot/agent/machine.cxx | 110 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 101 insertions(+), 9 deletions(-)

(limited to 'bbot/agent/machine.cxx')

diff --git a/bbot/agent/machine.cxx b/bbot/agent/machine.cxx
index fdc11c0..2566ca4 100644
--- a/bbot/agent/machine.cxx
+++ b/bbot/agent/machine.cxx
@@ -189,6 +189,9 @@ namespace bbot
     using machine::wait;
 
     virtual void
+    cleanup () override;
+
+    virtual void
     print_info (diag_record&) override;
 
   private:
@@ -202,6 +205,8 @@ namespace bbot
     tap net;      // Tap network interface.
     string vnc;   // QEMU VNC TCP addr:port.
     path monitor; // QEMU monitor UNIX socket.
+    path log;     // QEMU log (QMP read end).
+    auto_fd qmp;  // QMP write end.
     process proc;
   };
 
@@ -229,6 +234,18 @@ namespace bbot
     if (sizeof (sockaddr_un::sun_path) <= monitor.size ())
       throw invalid_argument ("monitor unix socket path too long");
 
+    // Machine name.
+    //
+    // While we currently can only have one running machine per toolchain, add
+    // the instance number for debuggability.
+    //
+    string name (mm.name + '-' + tc_name + '-' + to_string (inst));
+
+    // Machine log. Note that it is only removed with an explicit cleanup()
+    // call.
+    //
+    log = path ("/tmp/" + path::traits::temp_name (name) + ".log");
+
     // Map logical CPUs to sockets/cores/threads keeping the number of and
     // cores even. Failed that, QEMU just makes it a machine with that number
     // of sockets and some operating systems (like Windows) can only do two.
@@ -315,20 +332,45 @@ namespace bbot
       //"-device", "scsi-hd,drive=disk0"
     }
 
-    // Start the VM.
+    // Setup QMP (QEMU Machine Protocol) monitor to act as a log.
     //
-    // Notes:
+    // Note that we still have to tell it our "capabilities" so while it will
+    // write to a log file, we need a pipe it will read from.
     //
-    // 1. echo system_powerdown | socat - UNIX-CONNECT:.../monitor
+    fdpipe qmp_in;
+    try
+    {
+      qmp_in = fdopen_pipe ();
+    }
+    catch (const io_error& e)
+    {
+      fail << "unable to create QMP input pipe: " << e;
+    }
+
+    auto_fd qmp_out;
+    try
+    {
+      qmp_out = fdopen (log, (fdopen_mode::out      |
+                              fdopen_mode::create   |
+                              fdopen_mode::exclusive));
+    }
+    catch (const io_error& e)
+    {
+      fail << "unable to create QMP output file: " << e;
+    }
+
+    // Start the VM.
     //
     const char* env[] = {"QEMU_AUDIO_DRV=none", // Disable audio output.
                          nullptr};
     proc = run_io_start (
       trace,
-      fdnull (),
-      2,
-      2,
+      qmp_in,
+      2,       // 1>&2 (QMP goes to stdout)
+      qmp_out,
       process_env (kvm, md, env), // Run from the machine's directory.
+      "-name", name + ",debug-threads=on",
+      "-S",         // Start suspended.
       "-boot", "c", // Boot from disk.
       "-no-reboot", // Exit on VM reboot.
       "-m",   to_string (ram / 1024) + "M",
@@ -337,15 +379,64 @@ namespace bbot
                ",sockets=" + to_string (sockets) +
                ",cores="   + to_string (cores) +
                ",threads=" + to_string (threads)),
-      //
+
       // RTC settings.
       //
       "-rtc", "clock=vm,driftfix=slew",
       "-no-hpet",
       "-global", "kvm-pit.lost_tick_policy=discard",
+
       os,
+
+      // VNC.
+      //
       "-vnc", "127.0.0.1:" + to_string (offset), // 5900 + offset
-      "-monitor", "unix:" + monitor.string () + ",server,nowait");
+
+      // QMP.
+      //
+      "-chardev", "stdio,id=qmp",
+      "-mon",     "chardev=qmp,mode=control,pretty=on",
+
+      // Monitor.
+      //
+      "-chardev", "socket,id=mon,path=" + monitor.string () + ",server,nowait",
+      "-mon",     "chardev=mon,mode=readline");
+
+    qmp_out.close ();
+    qmp_in.in.close ();
+    qmp = move (qmp_in.out);
+
+    // Wait for the QMP greeting. One day we will find a better way.
+    //
+    sleep (1);
+
+    try
+    {
+      ofdstream os (move (qmp));
+      os << "{ \"execute\": \"qmp_capabilities\" }" << endl;
+      qmp = os.release ();
+    }
+    catch (const io_error& e)
+    {
+      fail << "unable to initialize QMP: " << e;
+    }
+
+    // Start execution.
+    //
+    try
+    {
+      monitor_command ("cont");
+    }
+    catch (const system_error& e)
+    {
+      fail << "unable to communicate with qemu monitor: " << e;
+    }
+  }
+
+  void kvm_machine::
+  cleanup ()
+  {
+    try_rmfile (log, true /* ignore_errors */);
   }
 
   // Connect to the QEMU monitor via the UNIX socket and send system_reset.
@@ -434,6 +525,7 @@ namespace bbot
   print_info (diag_record& dr)
   {
     dr << info << "qemu pid: " << proc.id ()
+       << info << "qemu log: " << log
        << info << "qemu vnc: " << vnc
        << info << "qemu monitor: unix:" << monitor;
   }
@@ -453,7 +545,7 @@ namespace bbot
       {
         run_io_finish (trace, proc, kvm, fh);
         net.destroy (); //@@ Always fails hard.
-        try_rmfile (monitor, true); // QEMU doesn't seem to remove it.
+        try_rmfile (monitor, true /* ignore_errors */); // QEMU doesn't do it.
       }
 
       return t;
-- 
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