1 files changed, 38 insertions, 7 deletions

diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 2c8d0e7219..a8aed9cb3a 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -1948,28 +1948,59 @@ PropertyInfo css_devid_ro_propinfo = {
     .get = get_css_devid,
 };
 
-SubchDev *css_create_virtual_sch(CssDevId bus_id, Error **errp)
+SubchDev *css_create_sch(CssDevId bus_id, bool is_virtual, bool squash_mcss,
+                         Error **errp)
 {
     uint16_t schid = 0;
     SubchDev *sch;
 
     if (bus_id.valid) {
-        /* Enforce use of virtual cssid. */
-        if (bus_id.cssid != VIRTUAL_CSSID) {
-            error_setg(errp, "cssid %hhx not valid for virtual devices",
-                       bus_id.cssid);
+        if (is_virtual != (bus_id.cssid == VIRTUAL_CSSID)) {
+            error_setg(errp, "cssid %hhx not valid for %s devices",
+                       bus_id.cssid,
+                       (is_virtual ? "virtual" : "non-virtual"));
             return NULL;
         }
+    }
+
+    if (bus_id.valid) {
+        if (squash_mcss) {
+            bus_id.cssid = channel_subsys.default_cssid;
+        } else if (!channel_subsys.css[bus_id.cssid]) {
+            css_create_css_image(bus_id.cssid, false);
+        }
+
         if (!css_find_free_subch_for_devno(bus_id.cssid, bus_id.ssid,
                                            bus_id.devid, &schid, errp)) {
             return NULL;
         }
-    } else {
-        bus_id.cssid = VIRTUAL_CSSID;
+    } else if (squash_mcss || is_virtual) {
+        bus_id.cssid = channel_subsys.default_cssid;
+
         if (!css_find_free_subch_and_devno(bus_id.cssid, &bus_id.ssid,
                                            &bus_id.devid, &schid, errp)) {
             return NULL;
         }
+    } else {
+        for (bus_id.cssid = 0; bus_id.cssid < MAX_CSSID; ++bus_id.cssid) {
+            if (bus_id.cssid == VIRTUAL_CSSID) {
+                continue;
+            }
+
+            if (!channel_subsys.css[bus_id.cssid]) {
+                css_create_css_image(bus_id.cssid, false);
+            }
+
+            if   (css_find_free_subch_and_devno(bus_id.cssid, &bus_id.ssid,
+                                                &bus_id.devid, &schid,
+                                                NULL)) {
+                break;
+            }
+            if (bus_id.cssid == MAX_CSSID) {
+                error_setg(errp, "Virtual channel subsystem is full!");
+                return NULL;
+            }
+        }
     }
 
     sch = g_malloc0(sizeof(*sch));