This patch introduces libxl_primary_console_exec: a new libxl function

that finds the domid and console number corresponding to the primary
console of a given vm. The domid might be different from the domid of
the VM and the console number might not be 0 when using stubdoms.
The caller (xl_cmdimpl.c in this case) has to make sure that the stubdom
is already created before calling libxl_primary_console_exec in the hvm
case. In the PV case libxl_primary_console_exec has to be called before
libxl_run_bootloader.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/libxl/libxl.c

@@ -803,6 +803,15 @@ int libxl_console_exec(struct libxl_ctx *ctx, uint32_t domid, int cons_num)
     return execl(p, p, domid_s, "--num", cons_num_s, (void *)NULL) == 0 ? 0 : ERROR_FAIL;
 }
 
+int libxl_primary_console_exec(struct libxl_ctx *ctx, uint32_t domid_vm)
+{
+    uint32_t stubdomid = libxl_get_stubdom_id(ctx, domid_vm);
+    if (stubdomid)
+        return libxl_console_exec(ctx, stubdomid, 1);
+    else
+        return libxl_console_exec(ctx, domid_vm, 0);
+}
+
 static char ** libxl_build_device_model_args(struct libxl_ctx *ctx,
                                              libxl_device_model_info *info,
                                              libxl_device_nic *vifs,

tools/libxl/libxl.h

@@ -399,6 +399,14 @@ int libxl_domain_setmaxmem(struct libxl_ctx *ctx, uint32_t domid, uint32_t targe
 int libxl_set_memory_target(struct libxl_ctx *ctx, uint32_t domid, uint32_t target_memkb, int enforce);
 
 int libxl_console_exec(struct libxl_ctx *ctx, uint32_t domid, int cons_num);
+/* libxl_primary_console_exec finds the domid and console number
+ * corresponding to the primary console of the given vm, then calls
+ * libxl_console_exec with the right arguments (domid might be different
+ * if the guest is using stubdoms).
+ * This function can be called after creating the device model, in
+ * case of HVM guests, and before libxl_run_bootloader in case of PV
+ * guests using pygrub. */ 
+int libxl_primary_console_exec(struct libxl_ctx *ctx, uint32_t domid_vm);
 
 int libxl_domain_info(struct libxl_ctx*, struct libxl_dominfo *info_r,
                       uint32_t domid);

tools/libxl/xl_cmdimpl.c

@@ -947,9 +947,9 @@ static void *xrealloc(void *ptr, size_t sz) {
     return r;
 }
 
-int autoconnect_console(int cons_num)
+int autoconnect_console(int hvm)
 {
-    int status;
+    int status, options;
     pid_t pid, r;
 
     /*
@@ -966,14 +966,21 @@ int autoconnect_console(int cons_num)
         return 0;
 
     /*
-     * Catch failure of the create process.
+     * In the PV case we only catch failure of the create process, in
+     * the HVM case we also wait for the creation process to be
+     * completed so that the stubdom is already up and running and we
+     * can connect to it.
      */
+    if (hvm)
+        options = 0;
+    else
+        options = WNOHANG;
     sleep(1);
-    r = waitpid(pid, &status, WNOHANG);
+    r = waitpid(pid, &status, options);
     if (r > 0 && WIFEXITED(status) && WEXITSTATUS(status) != 0)
         _exit(WEXITSTATUS(status));
 
-    libxl_console_exec(&ctx, domid, cons_num);
+    libxl_primary_console_exec(&ctx, domid);
     /* Do not return. xl continued in child process */
     fprintf(stderr, "Unable to attach console\n");
     _exit(1);
@@ -1170,7 +1177,7 @@ start:
     }
 
     if (dom_info->console_autoconnect) {
-        ret = autoconnect_console(0);
+        ret = autoconnect_console(info1.hvm);
         if (ret)
             goto error_out;
     }
@@ -1624,18 +1631,13 @@ int main_cd_insert(int argc, char **argv)
 
 int main_console(int argc, char **argv)
 {
-    int opt = 0, cons_num = 0;
+    int opt = 0;
 
     while ((opt = getopt(argc, argv, "hn:")) != -1) {
         switch (opt) {
         case 'h':
             help("console");
             exit(0);
-        case 'n':
-            if (optarg) {
-                cons_num = strtol(optarg, NULL, 10);
-            }
-            break;
         default:
             fprintf(stderr, "option not supported\n");
             break;
@@ -1647,7 +1649,7 @@ int main_console(int argc, char **argv)
     }
 
     find_domain(argv[optind]);
-    libxl_console_exec(&ctx, domid, 0);
+    libxl_primary_console_exec(&ctx, domid);
     fprintf(stderr, "Unable to attach console\n");
     return 1;
 }