xl: provide a command to set the saved configuration for a running domain

Pickup this new configuration on reboot.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

docs/man/xl.pod.1

@@ -148,6 +148,31 @@ soon as it is run.
 
 =back
 
+=item B<config-update> B<domid> [I<configfile>] [I<OPTIONS>]
+
+Update the saved configuration for a running domain. This has no
+immediate effect but will be applied when the guest is next
+restarted. This command is useful to ensure that runtime modifications
+made to the guest will be preserved when the guest is restarted.
+
+I<configfile> has to be an absolute path to a file.
+
+B<OPTIONS>
+
+=over 4 
+
+=item B<-f=FILE>, B<--defconfig=FILE>
+
+Use the given configuration file.
+
+=item B<key=value>
+
+It is possible to pass I<key=value> pairs on the command line to provide
+options as if they were written in the configuration file; these override
+whatever is in the I<configfile>.
+
+=back
+
 =item B<console> [I<OPTIONS>] I<domain-id>
 
 Attach to domain I<domain-id>'s console.  If you've set up your domains to

tools/libxl/xl.h

@@ -50,6 +50,7 @@ int main_reboot(int argc, char **argv);
 int main_list(int argc, char **argv);
 int main_list_vm(int argc, char **argv);
 int main_create(int argc, char **argv);
+int main_config_update(int argc, char **argv);
 int main_button_press(int argc, char **argv);
 int main_vcpupin(int argc, char **argv);
 int main_vcpuset(int argc, char **argv);

tools/libxl/xl_cmdimpl.c

@@ -1206,11 +1206,31 @@ skip_vfb:
     xlu_cfg_destroy(config);
 }
 
+static void reload_domain_config(libxl_ctx *ctx, uint32_t domid,
+                                 uint8_t **config_data, int *config_len)
+{
+    uint8_t *t_data;
+    int ret, t_len;
+
+    ret = libxl_userdata_retrieve(ctx, domid, "xl", &t_data, &t_len);
+    if (ret) {
+        LOG("failed to retrieve guest configuration (rc=%d). "
+            "reusing old configuration", ret);
+        return;
+    }
+
+    free(*config_data);
+    *config_data = t_data;
+    *config_len = t_len;
+}
+
 /* Returns 1 if domain should be restarted,
  * 2 if domain should be renamed then restarted, or 0 */
 static int handle_domain_death(libxl_ctx *ctx, uint32_t domid,
                                libxl_event *event,
+                               uint8_t **config_data, int *config_len,
                                libxl_domain_config *d_config)
+
 {
     int restart = 0;
     libxl_action_on_shutdown action;
@@ -1265,10 +1285,13 @@ static int handle_domain_death(libxl_ctx *ctx, uint32_t domid,
         break;
 
     case LIBXL_ACTION_ON_SHUTDOWN_RESTART_RENAME:
+        reload_domain_config(ctx, domid, config_data, config_len);
         restart = 2;
         break;
 
     case LIBXL_ACTION_ON_SHUTDOWN_RESTART:
+        reload_domain_config(ctx, domid, config_data, config_len);
+
         restart = 1;
         /* fall-through */
     case LIBXL_ACTION_ON_SHUTDOWN_DESTROY:
@@ -1753,7 +1776,9 @@ start:
             LOG("Domain %d has shut down, reason code %d 0x%x", domid,
                 event->u.domain_shutdown.shutdown_reason,
                 event->u.domain_shutdown.shutdown_reason);
-            switch (handle_domain_death(ctx, domid, event, &d_config)) {
+            switch (handle_domain_death(ctx, domid, event,
+                                        (uint8_t **)&config_data, &config_len,
+                                        &d_config)) {
             case 2:
                 if (!preserve_domain(ctx, domid, event, &d_config)) {
                     /* If we fail then exit leaving the old domain in place. */
@@ -1790,6 +1815,12 @@ start:
                     d_config.c_info.name = strdup(common_domname);
                 }
 
+                /* Reparse the configuration in case it has changed */
+                libxl_domain_config_dispose(&d_config);
+                memset(&d_config, 0, sizeof(d_config));
+                parse_config_data(config_file, config_data, config_len,
+                                  &d_config);
+
                 /*
                  * XXX FIXME: If this sleep is not there then domain
                  * re-creation fails sometimes.
@@ -3399,6 +3430,120 @@ int main_create(int argc, char **argv)
     return 0;
 }
 
+int main_config_update(int argc, char **argv)
+{
+    const char *filename = NULL;
+    char *p;
+    char extra_config[1024];
+    void *config_data = 0;
+    int config_len = 0;
+    libxl_domain_config d_config;
+    int opt, rc;
+    int option_index = 0;
+    int debug = 0;
+    static struct option long_options[] = {
+        {"help", 0, 0, 'h'},
+        {"defconfig", 1, 0, 'f'},
+        {0, 0, 0, 0}
+    };
+
+    if (argc < 2) {
+        fprintf(stderr, "xl config-update requires a domain argument\n");
+        help("config-update");
+        exit(1);
+    }
+
+    find_domain(argv[1]);
+    argc--; argv++;
+
+    if (argv[1] && argv[1][0] != '-' && !strchr(argv[1], '=')) {
+        filename = argv[1];
+        argc--; argv++;
+    }
+
+    while (1) {
+        opt = getopt_long(argc, argv, "dhqf:", long_options, &option_index);
+        if (opt == -1)
+            break;
+
+        switch (opt) {
+        case 'd':
+            debug = 1;
+            break;
+        case 'f':
+            filename = optarg;
+            break;
+        case 'h':
+            help("create");
+            return 0;
+        default:
+            fprintf(stderr, "option `%c' not supported.\n", optopt);
+            break;
+        }
+    }
+
+    extra_config[0] = '\0';
+    for (p = extra_config; optind < argc; optind++) {
+        if (strchr(argv[optind], '=') != NULL) {
+            p += snprintf(p, sizeof(extra_config) - (p - extra_config),
+                "%s\n", argv[optind]);
+        } else if (!filename) {
+            filename = argv[optind];
+        } else {
+            help("create");
+            return 2;
+        }
+    }
+    if (filename) {
+        free(config_data);  config_data = 0;
+        rc = libxl_read_file_contents(ctx, filename,
+                                      &config_data, &config_len);
+        if (rc) { fprintf(stderr, "Failed to read config file: %s: %s\n",
+                           filename, strerror(errno)); return ERROR_FAIL; }
+        if (strlen(extra_config)) {
+            if (config_len > INT_MAX - (strlen(extra_config) + 2 + 1)) {
+                fprintf(stderr, "Failed to attach extra configration\n");
+                exit(1);
+            }
+            /* allocate space for the extra config plus two EOLs plus \0 */
+            config_data = realloc(config_data, config_len
+                + strlen(extra_config) + 2 + 1);
+            if (!config_data) {
+                fprintf(stderr, "Failed to realloc config_data\n");
+                exit(1);
+            }
+            config_len += sprintf(config_data + config_len, "\n%s\n",
+                extra_config);
+        }
+    } else {
+        fprintf(stderr, "Config file not specified\n");
+        exit(1);
+    }
+
+    memset(&d_config, 0x00, sizeof(d_config));
+
+    parse_config_data(filename, config_data, config_len, &d_config);
+
+    if (debug || dryrun_only)
+        printf_info(default_output_format, -1, &d_config);
+
+    if (!dryrun_only) {
+        fprintf(stderr, "setting dom%d configuration\n", domid);
+        rc = libxl_userdata_store(ctx, domid, "xl",
+                                   config_data, config_len);
+        if (rc) {
+            fprintf(stderr, "failed to update configuration\n");
+            exit(1);
+        }
+    }
+
+    libxl_domain_config_dispose(&d_config);
+
+    free(config_data);
+
+    return 0;
+}
+
 static void button_press(const char *p, const char *b)
 {
     libxl_trigger trigger;
@@ -3921,7 +4066,6 @@ static int sched_credit_domain_set(int domid, libxl_sched_credit_domain *scinfo)
 {
     int rc;
 
-    
     rc = libxl_sched_credit_domain_set(ctx, domid, scinfo);
     if (rc)
         fprintf(stderr, "libxl_sched_credit_domain_set failed.\n");

tools/libxl/xl_cmdtable.c

@@ -32,6 +32,15 @@ struct cmd_spec cmd_table[] = {
       "-d                      Enable debug messages.\n"
       "-e                      Do not wait in the background for the death of the domain."
     },
+    { "config-update",
+      &main_config_update, 1,
+      "Update a running domain's saved configuration, used when rebuilding "
+      "the domain after reboot",
+      "<Domain> <ConfigFile> [options] [vars]",
+      "-h                      Print this help.\n"
+      "-f FILE, --defconfig=FILE\n                     Use the given configuration file.\n"
+      "-d                      Enable debug messages.\n"
+    },
     { "list",
       &main_list, 0,
       "List information about all/some domains",