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Re: [Qemu-devel] [V4 PATCH 2/5] net: announce self after vm start


From: Jason Wang
Subject: Re: [Qemu-devel] [V4 PATCH 2/5] net: announce self after vm start
Date: Thu, 15 Mar 2012 14:08:09 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2

On 03/13/2012 05:18 PM, Paolo Bonzini wrote:
Il 13/03/2012 09:56, Jason Wang ha scritto:
This patch moves qemu_announce_self() to vm_start() and add a new parameters to
control whether sending gratuitous packet is needed. There are several reasons
to do this:

- Gratuitous packet is also needed when we resume a stopped vm or successfully
   load a state.
- Sending gratuitous packets may be done through co-operation with guest, so
   this work should be done after vm is started.

Signed-off-by: Jason Wang<address@hidden>
---
  gdbstub.c   |    2 +-
  migration.c |    5 ++---
  monitor.c   |    2 +-
  qmp.c       |    2 +-
  savevm.c    |    2 +-
  sysemu.h    |    2 +-
  vl.c        |    7 +++++--
  7 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index ef95ac2..f4d22e5 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -371,7 +371,7 @@ static inline void gdb_continue(GDBState *s)
  #ifdef CONFIG_USER_ONLY
      s->running_state = 1;
  #else
-    vm_start();
+    vm_start(false);
  #endif
Here we're switching from RUNSTATE_DEBUG.

  }

diff --git a/migration.c b/migration.c
index 00fa1e3..40332d2 100644
--- a/migration.c
+++ b/migration.c
@@ -88,14 +88,13 @@ void process_incoming_migration(QEMUFile *f)
          fprintf(stderr, "load of migration failed\n");
          exit(0);
      }
-    qemu_announce_self();
      DPRINTF("successfully loaded vm state\n");

      /* Make sure all file formats flush their mutable metadata */
      bdrv_invalidate_cache_all();

      if (autostart) {
-        vm_start();
+        vm_start(true);
Here from RUN_STATE_INMIGRATE.

      } else {
          runstate_set(RUN_STATE_PRELAUNCH);
      }
@@ -274,7 +273,7 @@ static void migrate_fd_put_ready(void *opaque)
          }
          if (s->state != MIG_STATE_COMPLETED) {
              if (old_vm_running) {
-                vm_start();
+                vm_start(false);
Here from RUN_STATE_FINISH_MIGRATE.

              }
          }
      }
diff --git a/monitor.c b/monitor.c
index cbdfbad..0b63c11 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2260,7 +2260,7 @@ static void do_loadvm(Monitor *mon, const QDict *qdict)
      vm_stop(RUN_STATE_RESTORE_VM);

      if (load_vmstate(name) == 0&&  saved_vm_running) {
-        vm_start();
+        vm_start(true);
Here from RUN_STATE_RESTORE_VM.

      }
  }

diff --git a/qmp.c b/qmp.c
index a182b51..252c842 100644
--- a/qmp.c
+++ b/qmp.c
@@ -160,7 +160,7 @@ void qmp_cont(Error **errp)
          return;
      }

-    vm_start();
+    vm_start(true);
Here from RUN_STATE_PAUSED or RUN_STATE_PRELAUNCH.

This introduces a difference here with "qemu -S" + cont, and "qemu".
The former will send a gratuitous ARP, the latter won't.  Is this
desired/harmless/...?

Not desired but harmless I think.

And indeed there're two possibilities:

- start a fresh vm with -S, and then continue the vm.
- migrate a guest with -S option used in destination, and then continue the vm.

It's a little hard to differentiate one from another just in vm_stop().

  }

  void qmp_system_wakeup(Error **errp)
diff --git a/savevm.c b/savevm.c
index 5b59826..82b9d3a 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2107,7 +2107,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)

   the_end:
      if (saved_vm_running)
-        vm_start();
+        vm_start(false);
  }
This is RUN_STATE_SAVE_VM.


  int load_vmstate(const char *name)
diff --git a/sysemu.h b/sysemu.h
index 98118cc..787edd4 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -34,7 +34,7 @@ void vm_state_notify(int running, RunState state);
  #define VMRESET_SILENT   false
  #define VMRESET_REPORT   true

-void vm_start(void);
+void vm_start(bool announce);
  void vm_stop(RunState state);
  void vm_stop_force_state(RunState state);

diff --git a/vl.c b/vl.c
index 65f11f2..4e04f82 100644
--- a/vl.c
+++ b/vl.c
@@ -1258,7 +1258,7 @@ void vm_state_notify(int running, RunState state)
      }
  }

-void vm_start(void)
+void vm_start(bool announce)
  {
      if (!runstate_is_running()) {
          cpu_enable_ticks();
@@ -1266,6 +1266,9 @@ void vm_start(void)
          vm_state_notify(1, RUN_STATE_RUNNING);
          resume_all_vcpus();
          monitor_protocol_event(QEVENT_RESUME, NULL);
+        if (announce) {
+            qemu_announce_self();
+        }
      }
  }

@@ -3619,7 +3622,7 @@ int main(int argc, char **argv, char **envp)
              exit(ret);
          }
      } else if (autostart) {
-        vm_start();
+        vm_start(false);
      }
This is RUN_STATE_PRELAUNCH.

To some up, it seems like whether to send an announcement depends on the
previous runstate: it should be sent only for RUN_STATE_INMIGRATE,
RUN_STATE_RESTORE_VM and (new with your patch) RUN_STATE_PAUSED.  So
perhaps the new argument to vm_start is not needed.

Paolo

Make sense, thanks.

      os_setup_post();







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