libxl: support dom0

In Xen, dom0 is really just another domain that supports ballooning,
adding/removing devices, changing vcpu configuration, etc. This patch
adds support to the libxl driver for managing dom0. Note that the
legacy xend driver has long supported managing dom0.

Operations that are not supported on dom0 are filtered in libvirt
where a sensible error is reported. Errors from libxl are not
always helpful. E.g., attempting a save on dom0 results in

2015-06-23 15:25:05 MDT libxl: debug: libxl_dom.c:1570:libxl__toolstack_save: domain=0 toolstack data size=8
2015-06-23 15:25:05 MDT libxl: debug: libxl.c:979:do_libxl_domain_suspend: ao 0x7f7e68000b70: inprogress: poller=0x7f7e68000930, flags=i
2015-06-23 15:25:05 MDT libxl-save-helper: debug: starting save: Success
2015-06-23 15:25:05 MDT xc: detail: xc_domain_save_suse: starting save of domid 0
2015-06-23 15:25:05 MDT xc: error: Couldn't map live_shinfo (3 = No such process): Internal error
2015-06-23 15:25:05 MDT xc: detail: Save exit of domid 0 with errno=3
2015-06-23 15:25:05 MDT libxl-save-helper: debug: complete r=1: No such process
2015-06-23 15:25:05 MDT libxl: error: libxl_dom.c:1876:libxl__xc_domain_save_done: saving domain: domain did not respond to suspend request: No such process
2015-06-23 15:25:05 MDT libxl: error: libxl_dom.c:2033:remus_teardown_done: Remus: failed to teardown device for guest with domid 0, rc -8
Signed-off-by: NJim Fehlig <jfehlig@suse.com>

src/libxl/libxl_driver.c

@@ -79,6 +79,15 @@ VIR_LOG_INIT("libxl.libxl_driver");
 /* Number of Xen scheduler parameters */
 #define XEN_SCHED_CREDIT_NPARAM   2
 
+#define LIBXL_CHECK_DOM0_GOTO(name, label)                               \
+    do {                                                                  \
+        if (STREQ_NULLABLE(name, "Domain-0")) {                           \
+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",               \
+                           _("Domain-0 does not support requested operation")); \
+            goto label;                                                   \
+        }                                                                 \
+    } while (0)
+
 
 static libxlDriverPrivatePtr libxl_driver;
 
@@ -500,6 +509,63 @@ const struct libxl_event_hooks ev_hooks = {
     .disaster = NULL,
 };
 
+static int
+libxlAddDom0(libxlDriverPrivatePtr driver)
+{
+    libxlDriverConfigPtr cfg = libxlDriverConfigGet(driver);
+    virDomainDefPtr def = NULL;
+    virDomainObjPtr vm = NULL;
+    virDomainDefPtr oldDef = NULL;
+    libxl_dominfo d_info;
+    int ret = -1;
+
+    libxl_dominfo_init(&d_info);
+
+    /* Ensure we have a dom0 */
+    if (libxl_domain_info(cfg->ctx, &d_info, 0) != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "%s", _("unable to get Domain-0 information from libxenlight"));
+        goto cleanup;
+    }
+
+    if (!(def = virDomainDefNew()))
+        goto cleanup;
+
+    def->id = 0;
+    def->virtType = VIR_DOMAIN_VIRT_XEN;
+    if (VIR_STRDUP(def->name, "Domain-0") < 0)
+        goto cleanup;
+
+    def->os.type = VIR_DOMAIN_OSTYPE_XEN;
+
+    if (virUUIDParse("00000000-0000-0000-0000-000000000000", def->uuid) < 0)
+        goto cleanup;
+
+    if (!(vm = virDomainObjListAdd(driver->domains, def,
+                                   driver->xmlopt,
+                                   0,
+                                   &oldDef)))
+        goto cleanup;
+
+    def = NULL;
+
+    vm->def->vcpus = d_info.vcpu_online;
+    vm->def->maxvcpus = d_info.vcpu_max_id + 1;
+    vm->def->mem.cur_balloon = d_info.current_memkb;
+    vm->def->mem.max_balloon = d_info.max_memkb;
+
+    ret = 0;
+
+ cleanup:
+    libxl_dominfo_dispose(&d_info);
+    virDomainDefFree(def);
+    virDomainDefFree(oldDef);
+    if (vm)
+        virObjectUnlock(vm);
+    virObjectUnref(cfg);
+    return ret;
+}
+
 static int
 libxlStateInitialize(bool privileged,
                      virStateInhibitCallback callback ATTRIBUTE_UNUSED,
@@ -616,6 +682,10 @@ libxlStateInitialize(bool privileged,
     if (!(libxl_driver->xmlopt = libxlCreateXMLConf()))
         goto error;
 
+    /* Add Domain-0 */
+    if (libxlAddDom0(libxl_driver) < 0)
+        goto error;
+
     /* Load running domains first. */
     if (virDomainObjListLoadAllConfigs(libxl_driver->domains,
                                        cfg->stateDir,
@@ -1030,6 +1100,8 @@ libxlDomainSuspend(virDomainPtr dom)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainSuspendEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -1086,6 +1158,8 @@ libxlDomainResume(virDomainPtr dom)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainResumeEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -1147,6 +1221,8 @@ libxlDomainShutdownFlags(virDomainPtr dom, unsigned int flags)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
         goto cleanup;
 
@@ -1212,6 +1288,8 @@ libxlDomainReboot(virDomainPtr dom, unsigned int flags)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainRebootEnsureACL(dom->conn, vm->def, flags) < 0)
         goto cleanup;
 
@@ -1254,6 +1332,8 @@ libxlDomainDestroyFlags(virDomainPtr dom,
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainDestroyFlagsEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -1656,6 +1736,8 @@ libxlDomainSaveFlags(virDomainPtr dom, const char *to, const char *dxml,
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainSaveFlagsEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -1782,6 +1864,8 @@ libxlDomainCoreDump(virDomainPtr dom, const char *to, unsigned int flags)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainCoreDumpEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -1877,6 +1961,8 @@ libxlDomainManagedSave(virDomainPtr dom, unsigned int flags)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainManagedSaveEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -4000,6 +4086,8 @@ libxlDomainSetAutostart(virDomainPtr dom, int autostart)
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainSetAutostartEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -4294,6 +4382,8 @@ libxlDomainOpenConsole(virDomainPtr dom,
     if (!(vm = libxlDomObjFromDomain(dom)))
         goto cleanup;
 
+    LIBXL_CHECK_DOM0_GOTO(vm->def->name, cleanup);
+
     if (virDomainOpenConsoleEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
@@ -4817,6 +4907,12 @@ libxlDomainMigrateBegin3Params(virDomainPtr domain,
     if (!(vm = libxlDomObjFromDomain(domain)))
         return NULL;
 
+    if (STREQ_NULLABLE(vm->def->name, "Domain-0")) {
+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                           _("Domain-0 cannot be migrated"));
+            return NULL;
+    }
+
     if (virDomainMigrateBegin3ParamsEnsureACL(domain->conn, vm->def) < 0) {
         virObjectUnlock(vm);
         return NULL;