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Re: [libvirt] [PATCH 4/4] qemu: query command line options in QMP



On 27/04/13 05:01, Eric Blake wrote:
Ever since the conversion to using only QMP for probing features
of qemu 1.2 and newer, we have been unable to detect features
that are added only by additional command line options.  For
example, we'd like to know if '-machine mem-merge=on' (added
in qemu 1.5) is present.  To do this, we will take advantage
of qemu 1.5's query-command-line-parameters QMP call [1].

This patch wires up the framework for probing the command results;
if the QMP command is missing, or if a particular command line
option does not output any parameters (for example, -net uses
an old-style parser, so it shows up with no parameters), we
silently treat that command as having no results.

[1] https://lists.gnu.org/archive/html/qemu-devel/2013-04/msg05180.html

* src/qemu/qemu_monitor.h (qemuMonitorGetOptions)
(qemuMonitorSetOptions)
(qemuMonitorGetCommandLineOptionParameters): New functions.
* src/qemu/qemu_monitor_json.h
(qemuMonitorJSONGetCommandLineOptionParameters): Likewise.
* src/qemu/qemu_monitor.c (_qemuMonitor): Add cache field.
(qemuMonitorDispose): Clean it.
(qemuMonitorGetCommandLineOptionParameters): Implement new function.
* src/qemu/qemu_monitor_json.c
(qemuMonitorJSONGetCommandLineOptionParameters): Likewise.
(testQemuMonitorJSONGetCommandLineParameters): Test it.

Signed-off-by: Eric Blake <eblake redhat com>
---
  src/qemu/qemu_monitor.c      |  41 +++++++++++++++
  src/qemu/qemu_monitor.h      |   9 +++-
  src/qemu/qemu_monitor_json.c | 123 +++++++++++++++++++++++++++++++++++++++++++
  src/qemu/qemu_monitor_json.h |   4 ++
  tests/qemumonitorjsontest.c  | 103 ++++++++++++++++++++++++++++++++++++
  5 files changed, 279 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index 5f714d6..fffd4cd 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -78,6 +78,9 @@ struct _qemuMonitor {

      bool json;
      bool waitGreeting;
+
+    /* cache of query-command-line-options results */
+    virJSONValuePtr options;
  };

  static virClassPtr qemuMonitorClass;
@@ -242,6 +245,7 @@ static void qemuMonitorDispose(void *obj)
          (mon->cb->destroy)(mon, mon->vm);
      virCondDestroy(&mon->notify);
      VIR_FREE(mon->buffer);
+    virJSONValueFree(mon->options);
  }


@@ -911,6 +915,18 @@ cleanup:
  }


+virJSONValuePtr
+qemuMonitorGetOptions(qemuMonitorPtr mon)
+{
+    return mon->options;
+}
+
+void
+qemuMonitorSetOptions(qemuMonitorPtr mon, virJSONValuePtr options)
+{
+    mon->options = options;
+}
+
  int qemuMonitorHMPCommandWithFd(qemuMonitorPtr mon,
                                  const char *cmd,
                                  int scm_fd,
@@ -3333,6 +3349,31 @@ int qemuMonitorGetEvents(qemuMonitorPtr mon,
  }


+/* Collect the parameters associated with a given command line option.
+ * Return count of known parameters or -1 on error.  */
+int
+qemuMonitorGetCommandLineOptionParameters(qemuMonitorPtr mon,
+                                          const char *option,
+                                          char ***params)
+{
+    VIR_DEBUG("mon=%p option=%s params=%p", mon, option, params);
+
+    if (!mon) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                       _("monitor must not be NULL"));
+        return -1;
+    }
+
+    if (!mon->json) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("JSON monitor is required"));
+        return -1;
+    }
+
+    return qemuMonitorJSONGetCommandLineOptionParameters(mon, option, params);
+}
+
+
  int qemuMonitorGetKVMState(qemuMonitorPtr mon,
                             bool *enabled,
                             bool *present)
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 527da0a..8f9c182 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -162,12 +162,16 @@ int qemuMonitorSetCapabilities(qemuMonitorPtr mon);

  int qemuMonitorSetLink(qemuMonitorPtr mon,
                         const char *name,
-                       enum virDomainNetInterfaceLinkState state) ;
+                       enum virDomainNetInterfaceLinkState state);

  /* These APIs are for use by the internal Text/JSON monitor impl code only */
  char *qemuMonitorNextCommandID(qemuMonitorPtr mon);
  int qemuMonitorSend(qemuMonitorPtr mon,
                      qemuMonitorMessagePtr msg);
+virJSONValuePtr qemuMonitorGetOptions(qemuMonitorPtr mon)
+    ATTRIBUTE_NONNULL(1);
+void qemuMonitorSetOptions(qemuMonitorPtr mon, virJSONValuePtr options)
+    ATTRIBUTE_NONNULL(1);
  int qemuMonitorHMPCommandWithFd(qemuMonitorPtr mon,
                                  const char *cmd,
                                  int scm_fd,
@@ -664,6 +668,9 @@ int qemuMonitorGetCommands(qemuMonitorPtr mon,
                             char ***commands);
  int qemuMonitorGetEvents(qemuMonitorPtr mon,
                           char ***events);
+int qemuMonitorGetCommandLineOptionParameters(qemuMonitorPtr mon,
+                                              const char *option,
+                                              char ***params);

  int qemuMonitorGetKVMState(qemuMonitorPtr mon,
                             bool *enabled,
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 341b295..0423ec7 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -4275,6 +4275,129 @@ cleanup:
  }


+int
+qemuMonitorJSONGetCommandLineOptionParameters(qemuMonitorPtr mon,
+                                              const char *option,
+                                              char ***params)
+{
+    int ret;
+    virJSONValuePtr cmd;
+    virJSONValuePtr reply = NULL;
+    virJSONValuePtr data = NULL;
+    virJSONValuePtr array = NULL;
+    char **paramlist = NULL;
+    int n = 0;
+    size_t i;
+
+    *params = NULL;
+
+    /* query-command-line-options has fixed output for a given qemu
+     * binary; but since callers want to query parameters for one
+     * option at a time, we cache the option list from qemu.  */
+    if (!qemuMonitorGetOptions(mon)) {
+        if (!(cmd = qemuMonitorJSONMakeCommand("query-command-line-options",
+                                               NULL)))
+            return -1;
+
+        ret = qemuMonitorJSONCommand(mon, cmd, &reply);
+
+        if (ret == 0) {
+            if (qemuMonitorJSONHasError(reply, "CommandNotFound"))
+                goto cleanup;
+            ret = qemuMonitorJSONCheckError(cmd, reply);
+        }
+
+        if (ret < 0)
+            goto cleanup;
+
+        if (virJSONValueObjectRemoveKey(reply, "return", &array) <= 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("query-command-line-options reply was missing "
+                             "return data"));
+            goto cleanup;
+        }
+        qemuMonitorSetOptions(mon, array);
+    }
+
+    ret = -1;
+
+    array = qemuMonitorGetOptions(mon);

No need to get it when the options is cached. How about:

    if (!(array = qemuMonitorGetOptions(mon))) {
        .....
    }

+    if ((n = virJSONValueArraySize(array)) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("query-command-line-options reply data was not "

s/was/is/, ? I'm sure that I don't want to talk about English with you
though. :-)

+                         "an array"));
+        goto cleanup;
+    }
+
+    for (i = 0 ; i < n ; i++) {
+        virJSONValuePtr child = virJSONValueArrayGet(array, i);
+        const char *tmp;
+
+        if (!(tmp = virJSONValueObjectGetString(child, "option"))) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("query-command-line-options reply data was "

Likewise.

+                             "missing 'option'"));
+            goto cleanup;
+        }
+        if (STREQ(tmp, option)) {
+            data = virJSONValueObjectGet(child, "parameters");
+            break;
+        }
+    }
+
+    if (!data) {
+        /* Option not found; return 0 parameters rather than an error.  */
+        ret = 0;
+        goto cleanup;
+    }
+
+    if ((n = virJSONValueArraySize(data)) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("query-command-line-options parameter data was not "

Likewise.

+                         "an array"));
+        goto cleanup;
+    }
+
+    /* null-terminated list */
+    if (VIR_ALLOC_N(paramlist, n + 1) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    for (i = 0 ; i < n ; i++) {
+        virJSONValuePtr child = virJSONValueArrayGet(data, i);
+        const char *tmp;
+
+        if (!(tmp = virJSONValueObjectGetString(child, "name"))) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("query-command-line-options parameter data was "

Likwise.

+                             "missing 'name'"));
+            goto cleanup;
+        }
+
+        if (!(paramlist[i] = strdup(tmp))) {

This has to be changed to use VIR_STRDUP.

+            virReportOOMError();
+            goto cleanup;
+        }
+    }
+
+    ret = n;
+    *params = paramlist;
+
+cleanup:
+    /* If we failed before getting the JSON array of options, we (try)
+     * to cache an empty array to speed up the next failure.  */
+    if (!qemuMonitorGetOptions(mon))
+        qemuMonitorSetOptions(mon, virJSONValueNewArray());
+
+    if (ret < 0)
+        virStringFreeList(paramlist);
+    virJSONValueFree(cmd);
+    virJSONValueFree(reply);
+    return ret;
+}
+
+
  int qemuMonitorJSONGetKVMState(qemuMonitorPtr mon,
                                 bool *enabled,
                                 bool *present)
diff --git a/src/qemu/qemu_monitor_json.h b/src/qemu/qemu_monitor_json.h
index 5ee0d84..74e2476 100644
--- a/src/qemu/qemu_monitor_json.h
+++ b/src/qemu/qemu_monitor_json.h
@@ -319,6 +319,10 @@ int qemuMonitorJSONGetCommands(qemuMonitorPtr mon,
  int qemuMonitorJSONGetEvents(qemuMonitorPtr mon,
                               char ***events)
      ATTRIBUTE_NONNULL(2);
+int qemuMonitorJSONGetCommandLineOptionParameters(qemuMonitorPtr mon,
+                                                  const char *option,
+                                                  char ***params)
+    ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3);

  int qemuMonitorJSONGetKVMState(qemuMonitorPtr mon,
                                 bool *enabled,
diff --git a/tests/qemumonitorjsontest.c b/tests/qemumonitorjsontest.c
index 6f42598..c7f0536 100644
--- a/tests/qemumonitorjsontest.c
+++ b/tests/qemumonitorjsontest.c
@@ -494,6 +494,108 @@ cleanup:


  static int
+testQemuMonitorJSONGetCommandLineOptionParameters(const void *data)
+{
+    const virDomainXMLOptionPtr xmlopt = (virDomainXMLOptionPtr)data;
+    qemuMonitorTestPtr test = qemuMonitorTestNew(true, xmlopt);
+    int ret = -1;
+    char **params = NULL;
+    int nparams = 0;
+
+    if (!test)
+        return -1;
+
+    if (qemuMonitorTestAddItem(test, "query-command-line-options",
+                               "{ "
+                               "  \"return\": [ "
+                               "  {\"parameters\": [], \"option\": \"acpi\" },"
+                               "  {\"parameters\": ["
+                               "    {\"name\": \"romfile\", "
+                               "     \"type\": \"string\"}, "
+                               "    {\"name\": \"bootindex\", "
+                               "     \"type\": \"number\"}], "
+                               "   \"option\": \"option-rom\"}"
+                               "  ]"
+                               "}") < 0)
+        goto cleanup;
+
+    /* present with params */
+    if ((nparams = qemuMonitorGetCommandLineOptionParameters(qemuMonitorTestGetMonitor(test),
+                                                             "option-rom",
+                                                             &params)) < 0)
+        goto cleanup;
+
+    if (nparams != 2) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "nparams %d is not 2", nparams);

This will produce something like "4 is not 2", which is obvious and confused. :/

"'nparams' is not 2" might be better.

+        goto cleanup;
+    }
+
+#define CHECK(i, wantname)                                              \
+    do {                                                                \
+        if (STRNEQ(params[i], (wantname))) {                            \
+            virReportError(VIR_ERR_INTERNAL_ERROR,                      \
+                           "name %s is not %s",                         \
+                           params[i], (wantname));                      \
+            goto cleanup;                                               \
+        }                                                               \
+    } while (0)
+
+    CHECK(0, "romfile");
+    CHECK(1, "bootindex");
+
+#undef CHECK
+
+    virStringFreeList(params);
+    params = NULL;
+
+    /* present but empty */
+    if ((nparams = qemuMonitorGetCommandLineOptionParameters(qemuMonitorTestGetMonitor(test),
+                                                             "acpi",
+                                                             &params)) < 0)
+        goto cleanup;
+
+    if (nparams != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "nparams %d is not 0", nparams);

Likewise.

+        goto cleanup;
+    }
+    if (params && params[0]) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       "unexpected array contents");
+        goto cleanup;
+    }
+
+    virStringFreeList(params);
+    params = NULL;
+
+    /* no such option */
+    if ((nparams = qemuMonitorGetCommandLineOptionParameters(qemuMonitorTestGetMonitor(test),
+                                                             "foobar",
+                                                             &params)) < 0)
+        goto cleanup;
+
+    if (nparams != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "nparams %d is not 0", nparams);

Likewise.

ACK with the nits fixed.


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