libxl: detect support for save and restore

libxl does not support save, restore, or migrate on all architectures,
notably ARM.  Detect whether libxl supports these operations using
LIBXL_HAVE_NO_SUSPEND_RESUME.  If not supported, drop advertisement of
<migration_features>.

Found by Ian Campbell while improving Xen's OSSTEST infrastructure

http://lists.xen.org/archives/html/xen-devel/2014-06/msg02171.html

src/libxl/libxl_conf.c

@@ -1340,7 +1340,11 @@ libxlMakeCapabilities(libxl_ctx *ctx)
 {
     virCapsPtr caps;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    if ((caps = virCapabilitiesNew(virArchFromHost(), 0, 0)) == NULL)
+#else
     if ((caps = virCapabilitiesNew(virArchFromHost(), 1, 1)) == NULL)
+#endif
         return NULL;
 
     if (libxlCapsInitHost(ctx, caps) < 0)

src/libxl/libxl_driver.c

@@ -1379,6 +1379,11 @@ libxlDomainSaveFlags(virDomainPtr dom, const char *to, const char *dxml,
     int ret = -1;
     bool remove_dom = false;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return -1;
+#endif
+
     virCheckFlags(0, -1);
     if (dxml) {
         virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
@@ -1440,6 +1445,11 @@ libxlDomainRestoreFlags(virConnectPtr conn, const char *from,
     int fd = -1;
     int ret = -1;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return -1;
+#endif
+
     virCheckFlags(VIR_DOMAIN_SAVE_PAUSED, -1);
     if (dxml) {
         virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
@@ -4351,6 +4361,11 @@ libxlDomainMigrateBegin3Params(virDomainPtr domain,
     const char *xmlin = NULL;
     virDomainObjPtr vm = NULL;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return NULL;
+#endif
+
     virCheckFlags(LIBXL_MIGRATION_FLAGS, NULL);
     if (virTypedParamsValidate(params, nparams, LIBXL_MIGRATION_PARAMETERS) < 0)
         return NULL;
@@ -4395,6 +4410,11 @@ libxlDomainMigratePrepare3Params(virConnectPtr dconn,
     const char *dname = NULL;
     const char *uri_in = NULL;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return -1;
+#endif
+
     virCheckFlags(LIBXL_MIGRATION_FLAGS, -1);
     if (virTypedParamsValidate(params, nparams, LIBXL_MIGRATION_PARAMETERS) < 0)
         goto error;
@@ -4445,6 +4465,11 @@ libxlDomainMigratePerform3Params(virDomainPtr dom,
     const char *uri = NULL;
     int ret = -1;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return -1;
+#endif
+
     virCheckFlags(LIBXL_MIGRATION_FLAGS, -1);
     if (virTypedParamsValidate(params, nparams, LIBXL_MIGRATION_PARAMETERS) < 0)
         goto cleanup;
@@ -4497,6 +4522,11 @@ libxlDomainMigrateFinish3Params(virConnectPtr dconn,
     virDomainObjPtr vm = NULL;
     const char *dname = NULL;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return NULL;
+#endif
+
     virCheckFlags(LIBXL_MIGRATION_FLAGS, NULL);
     if (virTypedParamsValidate(params, nparams, LIBXL_MIGRATION_PARAMETERS) < 0)
         return NULL;
@@ -4545,6 +4575,11 @@ libxlDomainMigrateConfirm3Params(virDomainPtr domain,
     libxlDriverPrivatePtr driver = domain->conn->privateData;
     virDomainObjPtr vm = NULL;
 
+#ifdef LIBXL_HAVE_NO_SUSPEND_RESUME
+    virReportUnsupportedError();
+    return -1;
+#endif
+
     virCheckFlags(LIBXL_MIGRATION_FLAGS, -1);
     if (virTypedParamsValidate(params, nparams, LIBXL_MIGRATION_PARAMETERS) < 0)
         return -1;