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[libvirt] [PATCH] [DRAFT] handle qemu event GUEST_PANICKED



This is for early review, comments are welcome!

qemu is adding a method to detect guest panic, and a new event
GUEST_PANICKED[1]. This patch adds support for GUEST_PANICKED.

But I have two questions:

  -  to react to GUEST_PANICKED, can xml element <on_crash> be
     used as the action to take, or do I have to invent another
     xml element to configure the action?

  -  Currently libvirt relies on watchdog to detect guest panic,
     but this way is not that reliable(there has to be a watchdog
     device, the watchdog itself has to be working when panic occurs),
     so it seems to be appropriate to remove this method from libvirt
     as there is a better one. But, will the removal cause any problems,
     such as backward compatibility, user confusion, etc.?


[1] http://lists.nongnu.org/archive/html/qemu-devel/2012-10/msg04361.html
---
 src/qemu/qemu_command.c      |   31 ++++++++++++++++++++-----------
 src/qemu/qemu_monitor.c      |   10 ++++++++++
 src/qemu/qemu_monitor.h      |    3 +++
 src/qemu/qemu_monitor_json.c |    9 +++++++++
 src/qemu/qemu_process.c      |    9 +++++++++
 5 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 898c4c0..0c3f9ff 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4300,6 +4300,9 @@ qemuBuildMachineArgStr(virCommandPtr cmd,
                        const virDomainDefPtr def,
                        qemuCapsPtr caps)
 {
+    virBuffer params = VIR_BUFFER_INITIALIZER;
+    char *tmp = NULL;
+
     /* This should *never* be NULL, since we always provide
      * a machine in the capabilities data for QEMU. So this
      * check is just here as a safety in case the unexpected
@@ -4307,29 +4310,35 @@ qemuBuildMachineArgStr(virCommandPtr cmd,
     if (!def->os.machine)
         return 0;
 
-    if (!def->mem.dump_core) {
-        /* if no parameter to the machine type is needed, we still use
-         * '-M' to keep the most of the compatibility with older versions.
-         */
-        virCommandAddArgList(cmd, "-M", def->os.machine, NULL);
-    } else {
+    virBufferAsprintf(&params, ",enable_pv_event=on");
+
+    if (def->mem.dump_core) {
         if (!qemuCapsGet(caps, QEMU_CAPS_DUMP_GUEST_CORE)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                            "%s", _("dump-guest-core is not available "
                                    " with this QEMU binary"));
             return -1;
         }
+        virBufferAsprintf(&params,",%s",
+                          virDomainMemDumpTypeToString(def->mem.dump_core));
+    }
 
-        /* However, in case there is a parameter to be added, we need to
+    tmp = virBufferContentAndReset(&params);
+    if (!tmp || strlen(tmp) == 0) {
+        /* if no parameter to the machine type is needed, we still use
+         * '-M' to keep the most of the compatibility with older versions.
+         */
+        virCommandAddArgList(cmd, "-M", def->os.machine, NULL);
+    } else {
+        /* However, in case there are parameters to be added, we need to
          * use the "-machine" parameter because qemu is not parsing the
          * "-M" correctly */
         virCommandAddArg(cmd, "-machine");
-        virCommandAddArgFormat(cmd,
-                               "%s,dump-guest-core=%s",
-                               def->os.machine,
-                               virDomainMemDumpTypeToString(def->mem.dump_core));
+        virCommandAddArgFormat(cmd, "%s%s", def->os.machine, tmp);
     }
 
+    VIR_FREE(tmp);
+
     return 0;
 }
 
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index 2d9c44c..8ab7ed2 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -1146,6 +1146,16 @@ int qemuMonitorEmitBalloonChange(qemuMonitorPtr mon,
 }
 
 
+int qemuMonitorEmitPanic(qemuMonitorPtr mon)
+{
+    int ret = -1;
+    VIR_DEBUG("mon=%p", mon);
+
+    QEMU_MONITOR_CALLBACK(mon, ret, domainPanic, mon->vm);
+    return ret;
+}
+
+
 int qemuMonitorSetCapabilities(qemuMonitorPtr mon)
 {
     int ret;
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 8856d9f..ea0a474 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -138,6 +138,8 @@ struct _qemuMonitorCallbacks {
                                unsigned long long actual);
     int (*domainPMSuspendDisk)(qemuMonitorPtr mon,
                                virDomainObjPtr vm);
+    int (*domainPanic)(qemuMonitorPtr mon,
+                       virDomainObjPtr vm);
 };
 
 char *qemuMonitorEscapeArg(const char *in);
@@ -216,6 +218,7 @@ int qemuMonitorEmitBlockJob(qemuMonitorPtr mon,
 int qemuMonitorEmitBalloonChange(qemuMonitorPtr mon,
                                  unsigned long long actual);
 int qemuMonitorEmitPMSuspendDisk(qemuMonitorPtr mon);
+int qemuMonitorEmitPanic(qemuMonitorPtr mon);
 
 int qemuMonitorStartCPUs(qemuMonitorPtr mon,
                          virConnectPtr conn);
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index e495c0a..0adbefc 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -71,6 +71,8 @@ static void qemuMonitorJSONHandleBlockJobCompleted(qemuMonitorPtr mon, virJSONVa
 static void qemuMonitorJSONHandleBlockJobCanceled(qemuMonitorPtr mon, virJSONValuePtr data);
 static void qemuMonitorJSONHandleBalloonChange(qemuMonitorPtr mon, virJSONValuePtr data);
 static void qemuMonitorJSONHandlePMSuspendDisk(qemuMonitorPtr mon, virJSONValuePtr data);
+static void qemuMonitorJSONHandlePanic(qemuMonitorPtr mon, virJSONValuePtr data);
+
 
 typedef struct {
     const char *type;
@@ -83,6 +85,7 @@ static qemuEventHandler eventHandlers[] = {
     { "BLOCK_JOB_CANCELLED", qemuMonitorJSONHandleBlockJobCanceled, },
     { "BLOCK_JOB_COMPLETED", qemuMonitorJSONHandleBlockJobCompleted, },
     { "DEVICE_TRAY_MOVED", qemuMonitorJSONHandleTrayChange, },
+    { "GUEST_PANICKED", qemuMonitorJSONHandlePanic, },
     { "POWERDOWN", qemuMonitorJSONHandlePowerdown, },
     { "RESET", qemuMonitorJSONHandleReset, },
     { "RTC_CHANGE", qemuMonitorJSONHandleRTCChange, },
@@ -4417,3 +4420,9 @@ cleanup:
     virJSONValueFree(reply);
     return ret;
 }
+
+static void qemuMonitorJSONHandlePanic(qemuMonitorPtr mon,
+                                       virJSONValuePtr data ATTRIBUTE_UNUSED)
+{
+    qemuMonitorEmitPanic(mon);
+}
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 969e3ce..d3b37e0 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -1235,6 +1235,14 @@ qemuProcessHandlePMSuspendDisk(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
     return 0;
 }
 
+static int
+qemuProcessHandlePanic(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
+                       virDomainObjPtr vm ATTRIBUTE_UNUSED)
+{
+    VIR_WARN("guest panicked.");
+    return 0;
+}
+
 
 static qemuMonitorCallbacks monitorCallbacks = {
     .destroy = qemuProcessHandleMonitorDestroy,
@@ -1254,6 +1262,7 @@ static qemuMonitorCallbacks monitorCallbacks = {
     .domainPMSuspend = qemuProcessHandlePMSuspend,
     .domainBalloonChange = qemuProcessHandleBalloonChange,
     .domainPMSuspendDisk = qemuProcessHandlePMSuspendDisk,
+    .domainPanic = qemuProcessHandlePanic,
 };
 
 static int
-- 
1.7.10.2


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