qemu: Add function to get migration params for save

Introduce qemuMigrationParamsForSave() to create a
qemuMigrationParams object initialized with appropriate migration
capabilities and parameters for a save operation.

Note that mapped-ram capability also requires the multifd capability.
For now, the number of multifd channels is set to 1. Future work
to support parallel save/restore can set the number of channels to
a user-specified value.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

src/qemu/qemu_migration.c

@@ -7134,7 +7134,7 @@ qemuMigrationSrcToFile(virQEMUDriver *driver, virDomainObj *vm,
 
     /* Increase migration bandwidth to unlimited since target is a file.
      * Failure to change migration speed is not fatal. */
-    if (!(migParams = qemuMigrationParamsNew()))
+    if (!(migParams = qemuMigrationParamsForSave(false)))
         return -1;
 
     if (qemuMigrationParamsSetULL(migParams,

src/qemu/qemu_migration_params.c

@@ -792,6 +792,27 @@ qemuMigrationParamsFromFlags(virTypedParameterPtr params,
 }
 
 
+qemuMigrationParams *
+qemuMigrationParamsForSave(bool sparse)
+{
+    g_autoptr(qemuMigrationParams) saveParams = NULL;
+
+    if (!(saveParams = qemuMigrationParamsNew()))
+        return NULL;
+
+    if (sparse) {
+        if (virBitmapSetBit(saveParams->caps, QEMU_MIGRATION_CAP_MAPPED_RAM) < 0)
+            return NULL;
+        if (virBitmapSetBit(saveParams->caps, QEMU_MIGRATION_CAP_MULTIFD) < 0)
+            return NULL;
+        saveParams->params[QEMU_MIGRATION_PARAM_MULTIFD_CHANNELS].value.i = 1;
+        saveParams->params[QEMU_MIGRATION_PARAM_MULTIFD_CHANNELS].set = true;
+    }
+
+    return g_steal_pointer(&saveParams);
+}
+
+
 int
 qemuMigrationParamsDump(qemuMigrationParams *migParams,
                         virTypedParameterPtr *params,

src/qemu/qemu_migration_params.h

@@ -87,6 +87,9 @@ qemuMigrationParamsFromFlags(virTypedParameterPtr params,
                              unsigned int flags,
                              qemuMigrationParty party);
 
+qemuMigrationParams *
+qemuMigrationParamsForSave(bool sparse);
+
 int
 qemuMigrationParamsDump(qemuMigrationParams *migParams,
                         virTypedParameterPtr *params,