qemu_process: introduce qemuProcessCreatePretendCmd

This will skip few steps from qemuProcessStart in order to create only
qemu CMD.  Use a VIR_QEMU_PROCESS_START_PRETEND for all the qemuProcess*
functions called by this one to not modify or check host.

This new function will be used later on for XMLToNative API and also for
qemuxml2argvtest to make sure that both API and test uses the same code
as qemuProcessStart.

We need also update qemuProcessInit to wrap few lines of code with check
that VIR_QEMU_PROCESS_START_PRETEND that makes sense only for
qemuProcessStart.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_process.c

@@ -4480,6 +4480,10 @@ qemuProcessStartValidate(virQEMUDriverPtr driver,
  * Prepares the domain up to the point when priv->qemuCaps is initialized. The
  * function calls qemuProcessStop when needed.
  *
+ * Flag VIR_QEMU_PROCESS_START_PRETEND tells, that we don't want to actually
+ * start the domain but create a valid qemu command.  If some code shouldn't be
+ * executed in this case, make sure to check this flag.
+ *
  * Returns 0 on success, -1 on error.
  */
 int
@@ -4529,18 +4533,20 @@ qemuProcessInit(virQEMUDriverPtr driver,
     if (virDomainObjSetDefTransient(caps, driver->xmlopt, vm, true) < 0)
         goto stop;
 
-    vm->def->id = qemuDriverAllocateID(driver);
-    qemuDomainSetFakeReboot(driver, vm, false);
-    virDomainObjSetState(vm, VIR_DOMAIN_PAUSED, VIR_DOMAIN_PAUSED_STARTING_UP);
+    if (!(flags & VIR_QEMU_PROCESS_START_PRETEND)) {
+        vm->def->id = qemuDriverAllocateID(driver);
+        qemuDomainSetFakeReboot(driver, vm, false);
+        virDomainObjSetState(vm, VIR_DOMAIN_PAUSED, VIR_DOMAIN_PAUSED_STARTING_UP);
 
-    if (virAtomicIntInc(&driver->nactive) == 1 && driver->inhibitCallback)
-        driver->inhibitCallback(true, driver->inhibitOpaque);
+        if (virAtomicIntInc(&driver->nactive) == 1 && driver->inhibitCallback)
+            driver->inhibitCallback(true, driver->inhibitOpaque);
 
-    /* Run an early hook to set-up missing devices */
-    if (qemuProcessStartHook(driver, vm,
-                             VIR_HOOK_QEMU_OP_PREPARE,
-                             VIR_HOOK_SUBOP_BEGIN) < 0)
-        goto stop;
+        /* Run an early hook to set-up missing devices */
+        if (qemuProcessStartHook(driver, vm,
+                                 VIR_HOOK_QEMU_OP_PREPARE,
+                                 VIR_HOOK_SUBOP_BEGIN) < 0)
+            goto stop;
+    }
 
     if (qemuDomainSetPrivatePaths(&priv->libDir,
                                   &priv->channelTargetDir,
@@ -5539,6 +5545,56 @@ qemuProcessStart(virConnectPtr conn,
 }
 
 
+virCommandPtr
+qemuProcessCreatePretendCmd(virConnectPtr conn,
+                            virQEMUDriverPtr driver,
+                            virDomainObjPtr vm,
+                            const char *migrateURI,
+                            bool forceFips,
+                            bool standalone,
+                            unsigned int flags)
+{
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    virCommandPtr cmd = NULL;
+
+    virCheckFlagsGoto(VIR_QEMU_PROCESS_START_COLD |
+                      VIR_QEMU_PROCESS_START_PAUSED |
+                      VIR_QEMU_PROCESS_START_AUTODESTROY, cleanup);
+
+    flags |= VIR_QEMU_PROCESS_START_PRETEND;
+
+    if (qemuProcessInit(driver, vm, QEMU_ASYNC_JOB_NONE, !!migrateURI,
+                        false, flags) < 0)
+        goto cleanup;
+
+    if (qemuProcessPrepareDomain(conn, driver, vm, flags) < 0)
+        goto cleanup;
+
+    VIR_DEBUG("Building emulator command line");
+    cmd = qemuBuildCommandLine(conn,
+                               driver,
+                               NULL,
+                               vm->def,
+                               priv->monConfig,
+                               priv->monJSON,
+                               priv->qemuCaps,
+                               migrateURI,
+                               NULL,
+                               VIR_NETDEV_VPORT_PROFILE_OP_NO_OP,
+                               &buildCommandLineCallbacks,
+                               standalone,
+                               forceFips ? true : qemuCheckFips(),
+                               priv->autoNodeset,
+                               NULL,
+                               NULL,
+                               priv->libDir,
+                               priv->channelTargetDir);
+
+ cleanup:
+    return cmd;
+}
+
+
 int
 qemuProcessKill(virDomainObjPtr vm, unsigned int flags)
 {

src/qemu/qemu_process.h

@@ -81,6 +81,13 @@ int qemuProcessStart(virConnectPtr conn,
                      virNetDevVPortProfileOp vmop,
                      unsigned int flags);
 
+virCommandPtr qemuProcessCreatePretendCmd(virConnectPtr conn,
+                                          virQEMUDriverPtr driver,
+                                          virDomainObjPtr vm,
+                                          const char *migrateURI,
+                                          bool forceFips,
+                                          bool standalone,
+                                          unsigned int flags);
 
 int qemuProcessStartValidate(virQEMUDriverPtr driver,
                              virDomainObjPtr vm,