xl: add support to parse generic virtio device

This patch adds basic support for parsing generic Virtio backend.

An example of domain configuration for mmio based Virtio I2C device is:
virtio = ["type=virtio,device22,transport=mmio"]

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

tools/xl/xl_parse.c

@@ -1208,6 +1208,83 @@ out:
     if (rc) exit(EXIT_FAILURE);
 }
 
+static int parse_virtio_config(libxl_device_virtio *virtio, char *token)
+{
+    char *oparg;
+    int rc;
+
+    if (MATCH_OPTION("backend", token, oparg)) {
+        virtio->backend_domname = strdup(oparg);
+    } else if (MATCH_OPTION("type", token, oparg)) {
+        virtio->type = strdup(oparg);
+    } else if (MATCH_OPTION("transport", token, oparg)) {
+        rc = libxl_virtio_transport_from_string(oparg, &virtio->transport);
+        if (rc) return rc;
+    } else {
+        fprintf(stderr, "Unknown string \"%s\" in virtio spec\n", token);
+        return -1;
+    }
+
+    return 0;
+}
+
+static void parse_virtio_list(const XLU_Config *config,
+                              libxl_domain_config *d_config)
+{
+    XLU_ConfigList *virtios;
+    const char *item;
+    char *buf = NULL, *oparg, *str = NULL;
+    int rc;
+
+    if (!xlu_cfg_get_list (config, "virtio", &virtios, 0, 0)) {
+        int entry = 0;
+        while ((item = xlu_cfg_get_listitem(virtios, entry)) != NULL) {
+            libxl_device_virtio *virtio;
+            char *p;
+
+            virtio = ARRAY_EXTEND_INIT(d_config->virtios, d_config->num_virtios,
+                                       libxl_device_virtio_init);
+
+            buf = strdup(item);
+
+            p = strtok(buf, ",");
+            while (p != NULL)
+            {
+                while (*p == ' ') p++;
+
+                // Type may contain a comma, do special handling.
+                if (MATCH_OPTION("type", p, oparg)) {
+                    if (!strncmp(oparg, "virtio", strlen("virtio"))) {
+                        char *p2 = strtok(NULL, ",");
+                        str = malloc(strlen(p) + strlen(p2) + 2);
+
+                        strcpy(str, p);
+                        strcat(str, ",");
+                        strcat(str, p2);
+                        p = str;
+                    }
+                }
+
+                rc = parse_virtio_config(virtio, p);
+                if (rc) goto out;
+
+                free(str);
+                str = NULL;
+                p = strtok(NULL, ",");
+            }
+
+            entry++;
+            free(buf);
+        }
+    }
+
+    return;
+
+out:
+    free(buf);
+    if (rc) exit(EXIT_FAILURE);
+}
+
 void parse_config_data(const char *config_source,
                        const char *config_data,
                        int config_len,
@@ -2753,6 +2830,10 @@ skip_usbdev:
 
     parse_vkb_list(config, d_config);
 
+    d_config->virtios = NULL;
+    d_config->num_virtios = 0;
+    parse_virtio_list(config, d_config);
+
     xlu_cfg_get_defbool(config, "xend_suspend_evtchn_compat",
                         &c_info->xend_suspend_evtchn_compat, 0);