Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20150907' into staging

s390x fixes and improvements:
- various bugfixes (css/event-facility)
- more efficient adapter interrupt routes setup
- gdb enhancement
- sclp got treated with a lot of remodelling/cleanup

# gpg: Signature made Mon 07 Sep 2015 15:42:43 BST using RSA key ID C6F02FAF
# gpg: Good signature from "Cornelia Huck <huckc@linux.vnet.ibm.com>"
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>"

* remotes/cohuck/tags/s390x-20150907: (23 commits)
  s390/sclp: simplify calculation of rnmax
  s390/sclp: store the increment_size in the sclp device
  s390: unify allocation of initial memory
  s390: move memory calculation into the sclp device
  s390/sclp: ignore memory hotplug operations if it is disabled
  s390: disallow memory hotplug for the s390-virtio machine
  s390: no need to manually parse for slots and maxmem
  s390/sclp: move sclp_service_interrupt into the sclp device
  s390/sclp: move sclp_execute related functions into the SCLP class
  s390/sclp: introduce a root sclp device
  s390/sclp: temporarily fix unassignment/reassignment of memory subregions
  s390/sclp: replace sclp event types with proper defines
  s390/sclp: rework sclp event facility initialization + device realization
  sclp/s390: rework sclp cpu hotplug device notification
  s390x/gdb: support reading/writing of control registers
  s390x/kvm: make setting of in-kernel irq routes more efficient
  pc-bios/s390-ccw: rebuild image
  pc-bios/s390-ccw: Device detection in higher subchannel sets
  s390x/event-facility: fix location of receive mask
  s390x/css: start with cleared cstat/dstat
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

17 files changed, 427 insertions, 223 deletions

diff --git a/configure b/configure
index 21c4089c5c..d854936682 100755
--- a/configure
+++ b/configure
@@ -5392,7 +5392,7 @@ case "$target_name" in
     echo "TARGET_ABI32=y" >> $config_target_mak
   ;;
   s390x)
-    gdb_xml_files="s390x-core64.xml s390-acr.xml s390-fpr.xml s390-vx.xml"
+    gdb_xml_files="s390x-core64.xml s390-acr.xml s390-fpr.xml s390-vx.xml s390-cr.xml"
   ;;
   tricore)
   ;;
diff --git a/gdb-xml/s390-cr.xml b/gdb-xml/s390-cr.xml
new file mode 100644
index 0000000000..5246beaab3
--- /dev/null
+++ b/gdb-xml/s390-cr.xml
@@ -0,0 +1,26 @@
+<?xml version="1.0"?>
+<!-- Copyright 2015 IBM Corp.
+
+     This work is licensed under the terms of the GNU GPL, version 2 or
+     (at your option) any later version. See the COPYING file in the
+     top-level directory. -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.s390.cr">
+  <reg name="cr0" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr1" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr2" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr3" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr4" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr5" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr6" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr7" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr8" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr9" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr10" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr11" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr12" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr13" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr14" bitsize="64" type="uint64" group="control"/>
+  <reg name="cr15" bitsize="64" type="uint64" group="control"/>
+</feature>
diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
index b471e7a41e..48714f96a3 100644
--- a/hw/intc/s390_flic_kvm.c
+++ b/hw/intc/s390_flic_kvm.c
@@ -228,6 +228,8 @@ static int kvm_s390_add_adapter_routes(S390FLICState *fs,
         routes->gsi[i] = ret;
         routes->adapter.ind_offset++;
     }
+    kvm_irqchip_commit_routes(kvm_state);
+
     /* Restore passed-in structure to original state. */
     routes->adapter.ind_offset = ind_offset;
     return 0;
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 5df450e00b..c033612889 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -261,6 +261,9 @@ static CCW1 copy_ccw_from_guest(hwaddr addr, bool fmt1)
         ret.flags = tmp0.flags;
         ret.count = be16_to_cpu(tmp0.count);
         ret.cda = be16_to_cpu(tmp0.cda1) | (tmp0.cda0 << 16);
+        if ((ret.cmd_code & 0x0f) == CCW_CMD_TIC) {
+            ret.cmd_code &= 0x0f;
+        }
     }
     return ret;
 }
@@ -287,6 +290,10 @@ static int css_interpret_ccw(SubchDev *sch, hwaddr ccw_addr)
         ((ccw.cmd_code & 0xf0) != 0)) {
         return -EINVAL;
     }
+    if (!sch->ccw_fmt_1 && (ccw.count == 0) &&
+        (ccw.cmd_code != CCW_CMD_TIC)) {
+        return -EINVAL;
+    }
 
     if (ccw.flags & CCW_FLAG_SUSPEND) {
         return -EINPROGRESS;
@@ -392,6 +399,8 @@ static void sch_handle_start_func(SubchDev *sch, ORB *orb)
     path = 0x80;
 
     if (!(s->ctrl & SCSW_ACTL_SUSP)) {
+        s->cstat = 0;
+        s->dstat = 0;
         /* Look at the orb and try to execute the channel program. */
         assert(orb != NULL); /* resume does not pass an orb */
         p->intparm = orb->intparm;
diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
index 0c700effb1..ef2a05160a 100644
--- a/hw/s390x/event-facility.c
+++ b/hw/s390x/event-facility.c
@@ -27,12 +27,12 @@ typedef struct SCLPEventsBus {
 struct SCLPEventFacility {
     SysBusDevice parent_obj;
     SCLPEventsBus sbus;
+    SCLPEvent quiesce_event;
+    SCLPEvent cpu_hotplug_event;
     /* guest' receive mask */
     unsigned int receive_mask;
 };
 
-static SCLPEvent cpu_hotplug;
-
 /* return true if any child has event pending set */
 static bool event_pending(SCLPEventFacility *ef)
 {
@@ -240,12 +240,13 @@ static void read_event_data(SCLPEventFacility *ef, SCCB *sccb)
         sclp_active_selection_mask = sclp_cp_receive_mask;
         break;
     case SCLP_SELECTIVE_READ:
-        if (!(sclp_cp_receive_mask & be32_to_cpu(red->mask))) {
+        sclp_active_selection_mask = be32_to_cpu(red->mask);
+        if (!sclp_cp_receive_mask ||
+            (sclp_active_selection_mask & ~sclp_cp_receive_mask)) {
             sccb->h.response_code =
                     cpu_to_be16(SCLP_RC_INVALID_SELECTION_MASK);
             goto out;
         }
-        sclp_active_selection_mask = be32_to_cpu(red->mask);
         break;
     default:
         sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_FUNCTION);
@@ -286,8 +287,26 @@ out:
 
 #define TYPE_SCLP_EVENTS_BUS "s390-sclp-events-bus"
 
+static void sclp_events_bus_realize(BusState *bus, Error **errp)
+{
+    BusChild *kid;
+
+    /* TODO: recursive realization has to be done in common code */
+    QTAILQ_FOREACH(kid, &bus->children, sibling) {
+        DeviceState *dev = kid->child;
+
+        object_property_set_bool(OBJECT(dev), true, "realized", errp);
+        if (*errp) {
+            return;
+        }
+    }
+}
+
 static void sclp_events_bus_class_init(ObjectClass *klass, void *data)
 {
+    BusClass *bc = BUS_CLASS(klass);
+
+    bc->realize = sclp_events_bus_realize;
 }
 
 static const TypeInfo sclp_events_bus_info = {
@@ -324,26 +343,24 @@ static const VMStateDescription vmstate_event_facility = {
      }
 };
 
-static int init_event_facility(SCLPEventFacility *event_facility)
+static void init_event_facility(Object *obj)
 {
-    DeviceState *sdev = DEVICE(event_facility);
-    DeviceState *quiesce;
+    SCLPEventFacility *event_facility = EVENT_FACILITY(obj);
+    DeviceState *sdev = DEVICE(obj);
 
     /* Spawn a new bus for SCLP events */
     qbus_create_inplace(&event_facility->sbus, sizeof(event_facility->sbus),
                         TYPE_SCLP_EVENTS_BUS, sdev, NULL);
 
-    quiesce = qdev_create(&event_facility->sbus.qbus, "sclpquiesce");
-    if (!quiesce) {
-        return -1;
-    }
-    qdev_init_nofail(quiesce);
-
-    object_initialize(&cpu_hotplug, sizeof(cpu_hotplug), TYPE_SCLP_CPU_HOTPLUG);
-    qdev_set_parent_bus(DEVICE(&cpu_hotplug), BUS(&event_facility->sbus));
-    object_property_set_bool(OBJECT(&cpu_hotplug), true, "realized", NULL);
-
-    return 0;
+    object_initialize(&event_facility->quiesce_event, sizeof(SCLPEvent),
+                      TYPE_SCLP_QUIESCE);
+    qdev_set_parent_bus(DEVICE(&event_facility->quiesce_event),
+                        &event_facility->sbus.qbus);
+    object_initialize(&event_facility->cpu_hotplug_event, sizeof(SCLPEvent),
+                      TYPE_SCLP_CPU_HOTPLUG);
+    qdev_set_parent_bus(DEVICE(&event_facility->cpu_hotplug_event),
+                        &event_facility->sbus.qbus);
+    /* the facility will automatically realize the devices via the bus */
 }
 
 static void reset_event_facility(DeviceState *dev)
@@ -362,7 +379,6 @@ static void init_event_facility_class(ObjectClass *klass, void *data)
     dc->reset = reset_event_facility;
     dc->vmsd = &vmstate_event_facility;
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
-    k->init = init_event_facility;
     k->command_handler = command_handler;
     k->event_pending = event_pending;
 }
@@ -370,6 +386,7 @@ static void init_event_facility_class(ObjectClass *klass, void *data)
 static const TypeInfo sclp_event_facility_info = {
     .name          = TYPE_SCLP_EVENT_FACILITY,
     .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_init = init_event_facility,
     .instance_size = sizeof(SCLPEventFacility),
     .class_init    = init_event_facility_class,
     .class_size    = sizeof(SCLPEventFacilityClass),
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index e2a26e95b9..27a8360207 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -100,57 +100,31 @@ static void virtio_ccw_register_hcalls(void)
                                    virtio_ccw_hcall_early_printk);
 }
 
-static void ccw_init(MachineState *machine)
+void s390_memory_init(ram_addr_t mem_size)
 {
-    ram_addr_t my_ram_size = machine->ram_size;
     MemoryRegion *sysmem = get_system_memory();
     MemoryRegion *ram = g_new(MemoryRegion, 1);
-    sclpMemoryHotplugDev *mhd = init_sclp_memory_hotplug_dev();
+
+    /* allocate RAM for core */
+    memory_region_init_ram(ram, NULL, "s390.ram", mem_size, &error_abort);
+    vmstate_register_ram_global(ram);
+    memory_region_add_subregion(sysmem, 0, ram);
+
+    /* Initialize storage key device */
+    s390_skeys_init();
+}
+
+static void ccw_init(MachineState *machine)
+{
     int ret;
     VirtualCssBus *css_bus;
     DeviceState *dev;
-    QemuOpts *opts = qemu_opts_find(qemu_find_opts("memory"), NULL);
-    ram_addr_t pad_size = 0;
-    ram_addr_t maxmem = qemu_opt_get_size(opts, "maxmem", my_ram_size);
-    ram_addr_t standby_mem_size = maxmem - my_ram_size;
-    uint64_t kvm_limit;
-
-    /* The storage increment size is a multiple of 1M and is a power of 2.
-     * The number of storage increments must be MAX_STORAGE_INCREMENTS or fewer.
-     * The variable 'mhd->increment_size' is an exponent of 2 that can be
-     * used to calculate the size (in bytes) of an increment. */
-    mhd->increment_size = 20;
-    while ((my_ram_size >> mhd->increment_size) > MAX_STORAGE_INCREMENTS) {
-        mhd->increment_size++;
-    }
-    while ((standby_mem_size >> mhd->increment_size) > MAX_STORAGE_INCREMENTS) {
-        mhd->increment_size++;
-    }
 
-    /* The core and standby memory areas need to be aligned with
-     * the increment size.  In effect, this can cause the
-     * user-specified memory size to be rounded down to align
-     * with the nearest increment boundary. */
-    standby_mem_size = standby_mem_size >> mhd->increment_size
-                                        << mhd->increment_size;
-    my_ram_size = my_ram_size >> mhd->increment_size
-                              << mhd->increment_size;
-
-    /* let's propagate the changed ram size into the global variable. */
-    ram_size = my_ram_size;
-    machine->maxram_size = my_ram_size + standby_mem_size;
-
-    ret = s390_set_memory_limit(machine->maxram_size, &kvm_limit);
-    if (ret == -E2BIG) {
-        hw_error("qemu: host supports a maximum of %" PRIu64 " GB",
-                 kvm_limit >> 30);
-    } else if (ret) {
-        hw_error("qemu: setting the guest size failed");
-    }
+    s390_sclp_init();
+    s390_memory_init(machine->ram_size);
 
     /* get a BUS */
     css_bus = virtual_css_bus_init();
-    s390_sclp_init();
     s390_init_ipl_dev(machine->kernel_filename, machine->kernel_cmdline,
                       machine->initrd_filename, "s390-ccw.img", true);
     s390_flic_init();
@@ -163,25 +137,6 @@ static void ccw_init(MachineState *machine)
     /* register hypercalls */
     virtio_ccw_register_hcalls();
 
-    /* allocate RAM for core */
-    memory_region_init_ram(ram, NULL, "s390.ram", my_ram_size, &error_abort);
-    vmstate_register_ram_global(ram);
-    memory_region_add_subregion(sysmem, 0, ram);
-
-    /* If the size of ram is not on a MEM_SECTION_SIZE boundary,
-       calculate the pad size necessary to force this boundary. */
-    if (standby_mem_size) {
-        if (my_ram_size % MEM_SECTION_SIZE) {
-            pad_size = MEM_SECTION_SIZE - my_ram_size % MEM_SECTION_SIZE;
-        }
-        my_ram_size += standby_mem_size + pad_size;
-        mhd->pad_size = pad_size;
-        mhd->standby_mem_size = standby_mem_size;
-    }
-
-    /* Initialize storage key device */
-    s390_skeys_init();
-
     /* init CPUs */
     s390_init_cpus(machine->cpu_model);
 
diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
index 6cc6b5d5c4..e4000c92e1 100644
--- a/hw/s390x/s390-virtio.c
+++ b/hw/s390x/s390-virtio.c
@@ -23,6 +23,7 @@
 
 #include "hw/hw.h"
 #include "qapi/qmp/qerror.h"
+#include "qemu/error-report.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/blockdev.h"
 #include "sysemu/sysemu.h"
@@ -260,30 +261,20 @@ int gtod_load(QEMUFile *f, void *opaque, int version_id)
 /* PC hardware initialisation */
 static void s390_init(MachineState *machine)
 {
-    ram_addr_t my_ram_size = machine->ram_size;
-    MemoryRegion *sysmem = get_system_memory();
-    MemoryRegion *ram = g_new(MemoryRegion, 1);
-    int increment_size = 20;
+    ram_addr_t my_ram_size;
     void *virtio_region;
     hwaddr virtio_region_len;
     hwaddr virtio_region_start;
 
-    /*
-     * The storage increment size is a multiple of 1M and is a power of 2.
-     * The number of storage increments must be MAX_STORAGE_INCREMENTS or
-     * fewer.
-     */
-    while ((my_ram_size >> increment_size) > MAX_STORAGE_INCREMENTS) {
-        increment_size++;
+    if (machine->ram_slots) {
+        error_report("Memory hotplug not supported by the selected machine.");
+        exit(EXIT_FAILURE);
     }
-    my_ram_size = my_ram_size >> increment_size << increment_size;
-
-    /* let's propagate the changed ram size into the global variable. */
-    ram_size = my_ram_size;
+    s390_sclp_init();
+    my_ram_size = machine->ram_size;
 
     /* get a BUS */
     s390_bus = s390_virtio_bus_init(&my_ram_size);
-    s390_sclp_init();
     s390_init_ipl_dev(machine->kernel_filename, machine->kernel_cmdline,
                       machine->initrd_filename, ZIPL_FILENAME, false);
     s390_flic_init();
@@ -292,9 +283,7 @@ static void s390_init(MachineState *machine)
     s390_virtio_register_hcalls();
 
     /* allocate RAM */
-    memory_region_init_ram(ram, NULL, "s390.ram", my_ram_size, &error_abort);
-    vmstate_register_ram_global(ram);
-    memory_region_add_subregion(sysmem, 0, ram);
+    s390_memory_init(my_ram_size);
 
     /* clear virtio region */
     virtio_region_len = my_ram_size - ram_size;
@@ -305,9 +294,6 @@ static void s390_init(MachineState *machine)
     cpu_physical_memory_unmap(virtio_region, virtio_region_len, 1,
                               virtio_region_len);
 
-    /* Initialize storage key device */
-    s390_skeys_init();
-
     /* init CPUs */
     s390_init_cpus(machine->cpu_model);
 
diff --git a/hw/s390x/s390-virtio.h b/hw/s390x/s390-virtio.h
index cf687968b4..f389aa1a67 100644
--- a/hw/s390x/s390-virtio.h
+++ b/hw/s390x/s390-virtio.h
@@ -27,4 +27,5 @@ void s390_init_ipl_dev(const char *kernel_filename,
                        bool enforce_bios);
 void s390_create_virtio_net(BusState *bus, const char *name);
 void s390_nmi(NMIState *n, int cpu_index, Error **errp);
+void s390_memory_init(ram_addr_t mem_size);
 #endif
diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index b3a6c5e5a4..fd277e1bf0 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -17,37 +17,27 @@
 #include "exec/memory.h"
 #include "sysemu/sysemu.h"
 #include "exec/address-spaces.h"
-#include "qemu/config-file.h"
+#include "hw/boards.h"
 #include "hw/s390x/sclp.h"
 #include "hw/s390x/event-facility.h"
 #include "hw/s390x/s390-pci-bus.h"
 
-static inline SCLPEventFacility *get_event_facility(void)
+static inline SCLPDevice *get_sclp_device(void)
 {
-    ObjectProperty *op = object_property_find(qdev_get_machine(),
-                                              TYPE_SCLP_EVENT_FACILITY,
-                                              NULL);
-    assert(op);
-    return op->opaque;
+    return SCLP(object_resolve_path_type("", TYPE_SCLP, NULL));
 }
 
 /* Provide information about the configuration, CPUs and storage */
-static void read_SCP_info(SCCB *sccb)
+static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
 {
     ReadInfo *read_info = (ReadInfo *) sccb;
+    MachineState *machine = MACHINE(qdev_get_machine());
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
     CPUState *cpu;
     int cpu_count = 0;
     int i = 0;
-    int increment_size = 20;
     int rnsize, rnmax;
-    QemuOpts *opts = qemu_opts_find(qemu_find_opts("memory"), NULL);
-    int slots = qemu_opt_get_number(opts, "slots", 0);
-    int max_avail_slots = s390_get_memslot_count(kvm_state);
-
-    if (slots > max_avail_slots) {
-        slots = max_avail_slots;
-    }
+    int slots = MIN(machine->ram_slots, s390_get_memslot_count(kvm_state));
 
     CPU_FOREACH(cpu) {
         cpu_count++;
@@ -66,23 +56,8 @@ static void read_SCP_info(SCCB *sccb)
     read_info->facilities = cpu_to_be64(SCLP_HAS_CPU_INFO |
                                         SCLP_HAS_PCI_RECONFIG);
 
-    /*
-     * The storage increment size is a multiple of 1M and is a power of 2.
-     * The number of storage increments must be MAX_STORAGE_INCREMENTS or fewer.
-     */
-    while ((ram_size >> increment_size) > MAX_STORAGE_INCREMENTS) {
-        increment_size++;
-    }
-    rnmax = ram_size >> increment_size;
-
     /* Memory Hotplug is only supported for the ccw machine type */
     if (mhd) {
-        while ((mhd->standby_mem_size >> increment_size) >
-               MAX_STORAGE_INCREMENTS) {
-            increment_size++;
-        }
-        assert(increment_size == mhd->increment_size);
-
         mhd->standby_subregion_size = MEM_SECTION_SIZE;
         /* Deduct the memory slot already used for core */
         if (slots > 0) {
@@ -108,13 +83,11 @@ static void read_SCP_info(SCCB *sccb)
         }
         mhd->padded_ram_size = ram_size + mhd->pad_size;
         mhd->rzm = 1 << mhd->increment_size;
-        rnmax = ((ram_size + mhd->standby_mem_size + mhd->pad_size)
-             >> mhd->increment_size);
 
         read_info->facilities |= cpu_to_be64(SCLP_FC_ASSIGN_ATTACH_READ_STOR);
     }
 
-    rnsize = 1 << (increment_size - 20);
+    rnsize = 1 << (sclp->increment_size - 20);
     if (rnsize <= 128) {
         read_info->rnsize = rnsize;
     } else {
@@ -122,6 +95,7 @@ static void read_SCP_info(SCCB *sccb)
         read_info->rnsize2 = cpu_to_be32(rnsize);
     }
 
+    rnmax = machine->maxram_size >> sclp->increment_size;
     if (rnmax < 0x10000) {
         read_info->rnmax = cpu_to_be16(rnmax);
     } else {
@@ -132,14 +106,17 @@ static void read_SCP_info(SCCB *sccb)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_READ_COMPLETION);
 }
 
-static void read_storage_element0_info(SCCB *sccb)
+static void read_storage_element0_info(SCLPDevice *sclp, SCCB *sccb)
 {
     int i, assigned;
     int subincrement_id = SCLP_STARTING_SUBINCREMENT_ID;
     ReadStorageElementInfo *storage_info = (ReadStorageElementInfo *) sccb;
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
 
-    assert(mhd);
+    if (!mhd) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        return;
+    }
 
     if ((ram_size >> mhd->increment_size) >= 0x10000) {
         sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
@@ -158,12 +135,15 @@ static void read_storage_element0_info(SCCB *sccb)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_READ_COMPLETION);
 }
 
-static void read_storage_element1_info(SCCB *sccb)
+static void read_storage_element1_info(SCLPDevice *sclp, SCCB *sccb)
 {
     ReadStorageElementInfo *storage_info = (ReadStorageElementInfo *) sccb;
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
 
-    assert(mhd);
+    if (!mhd) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        return;
+    }
 
     if ((mhd->standby_mem_size >> mhd->increment_size) >= 0x10000) {
         sccb->h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
@@ -179,13 +159,17 @@ static void read_storage_element1_info(SCCB *sccb)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_STANDBY_READ_COMPLETION);
 }
 
-static void attach_storage_element(SCCB *sccb, uint16_t element)
+static void attach_storage_element(SCLPDevice *sclp, SCCB *sccb,
+                                   uint16_t element)
 {
     int i, assigned, subincrement_id;
     AttachStorageElement *attach_info = (AttachStorageElement *) sccb;
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
 
-    assert(mhd);
+    if (!mhd) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        return;
+    }
 
     if (element != 1) {
         sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
@@ -203,20 +187,26 @@ static void attach_storage_element(SCCB *sccb, uint16_t element)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_COMPLETION);
 }
 
-static void assign_storage(SCCB *sccb)
+static void assign_storage(SCLPDevice *sclp, SCCB *sccb)
 {
     MemoryRegion *mr = NULL;
     uint64_t this_subregion_size;
     AssignStorage *assign_info = (AssignStorage *) sccb;
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
-    assert(mhd);
-    ram_addr_t assign_addr = (assign_info->rn - 1) * mhd->rzm;
+    ram_addr_t assign_addr;
     MemoryRegion *sysmem = get_system_memory();
 
+    if (!mhd) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        return;
+    }
+    assign_addr = (assign_info->rn - 1) * mhd->rzm;
+
     if ((assign_addr % MEM_SECTION_SIZE == 0) &&
         (assign_addr >= mhd->padded_ram_size)) {
         /* Re-use existing memory region if found */
         mr = memory_region_find(sysmem, assign_addr, 1).mr;
+        memory_region_unref(mr);
         if (!mr) {
 
             MemoryRegion *standby_ram = g_new(MemoryRegion, 1);
@@ -242,6 +232,11 @@ static void assign_storage(SCCB *sccb)
             }
 
             memory_region_init_ram(standby_ram, NULL, id, this_subregion_size, &error_abort);
+            /* This is a hack to make memory hotunplug work again. Once we have
+             * subdevices, we have to unparent them when unassigning memory,
+             * instead of doing it via the ref count of the MemoryRegion. */
+            object_ref(OBJECT(standby_ram));
+            object_unparent(OBJECT(standby_ram));
             vmstate_register_ram_global(standby_ram);
             memory_region_add_subregion(sysmem, offset, standby_ram);
         }
@@ -252,15 +247,20 @@ static void assign_storage(SCCB *sccb)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_COMPLETION);
 }
 
-static void unassign_storage(SCCB *sccb)
+static void unassign_storage(SCLPDevice *sclp, SCCB *sccb)
 {
     MemoryRegion *mr = NULL;
     AssignStorage *assign_info = (AssignStorage *) sccb;
     sclpMemoryHotplugDev *mhd = get_sclp_memory_hotplug_dev();
-    assert(mhd);
-    ram_addr_t unassign_addr = (assign_info->rn - 1) * mhd->rzm;
+    ram_addr_t unassign_addr;
     MemoryRegion *sysmem = get_system_memory();
 
+    if (!mhd) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        return;
+    }
+    unassign_addr = (assign_info->rn - 1) * mhd->rzm;
+
     /* if the addr is a multiple of 256 MB */
     if ((unassign_addr % MEM_SECTION_SIZE == 0) &&
         (unassign_addr >= mhd->padded_ram_size)) {
@@ -269,6 +269,7 @@ static void unassign_storage(SCCB *sccb)
 
         /* find the specified memory region and destroy it */
         mr = memory_region_find(sysmem, unassign_addr, 1).mr;
+        memory_region_unref(mr);
         if (mr) {
             int i;
             int is_removable = 1;
@@ -287,8 +288,7 @@ static void unassign_storage(SCCB *sccb)
             }
             if (is_removable) {
                 memory_region_del_subregion(sysmem, mr);
-                object_unparent(OBJECT(mr));
-                g_free(mr);
+                object_unref(OBJECT(mr));
             }
         }
     }
@@ -296,7 +296,7 @@ static void unassign_storage(SCCB *sccb)
 }
 
 /* Provide information about the CPU */
-static void sclp_read_cpu_info(SCCB *sccb)
+static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB *sccb)
 {
     ReadCpuInfo *cpu_info = (ReadCpuInfo *) sccb;
     CPUState *cpu;
@@ -323,34 +323,35 @@ static void sclp_read_cpu_info(SCCB *sccb)
     sccb->h.response_code = cpu_to_be16(SCLP_RC_NORMAL_READ_COMPLETION);
 }
 
-static void sclp_execute(SCCB *sccb, uint32_t code)
+static void sclp_execute(SCLPDevice *sclp, SCCB *sccb, uint32_t code)
 {
-    SCLPEventFacility *ef = get_event_facility();
+    SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
+    SCLPEventFacility *ef = sclp->event_facility;
     SCLPEventFacilityClass *efc = EVENT_FACILITY_GET_CLASS(ef);
 
     switch (code & SCLP_CMD_CODE_MASK) {
     case SCLP_CMDW_READ_SCP_INFO:
     case SCLP_CMDW_READ_SCP_INFO_FORCED:
-        read_SCP_info(sccb);
+        sclp_c->read_SCP_info(sclp, sccb);
         break;
     case SCLP_CMDW_READ_CPU_INFO:
-        sclp_read_cpu_info(sccb);
+        sclp_c->read_cpu_info(sclp, sccb);
         break;
     case SCLP_READ_STORAGE_ELEMENT_INFO:
         if (code & 0xff00) {
-            read_storage_element1_info(sccb);
+            sclp_c->read_storage_element1_info(sclp, sccb);
         } else {
-            read_storage_element0_info(sccb);
+            sclp_c->read_storage_element0_info(sclp, sccb);
         }
         break;
     case SCLP_ATTACH_STORAGE_ELEMENT:
-        attach_storage_element(sccb, (code & 0xff00) >> 8);
+        sclp_c->attach_storage_element(sclp, sccb, (code & 0xff00) >> 8);
         break;
     case SCLP_ASSIGN_STORAGE:
-        assign_storage(sccb);
+        sclp_c->assign_storage(sclp, sccb);
         break;
     case SCLP_UNASSIGN_STORAGE:
-        unassign_storage(sccb);
+        sclp_c->unassign_storage(sclp, sccb);
         break;
     case SCLP_CMDW_CONFIGURE_PCI:
         s390_pci_sclp_configure(1, sccb);
@@ -366,6 +367,8 @@ static void sclp_execute(SCCB *sccb, uint32_t code)
 
 int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
 {
+    SCLPDevice *sclp = get_sclp_device();
+    SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
     int r = 0;
     SCCB work_sccb;
 
@@ -400,20 +403,20 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
         goto out;
     }
 
-    sclp_execute((SCCB *)&work_sccb, code);
+    sclp_c->execute(sclp, (SCCB *)&work_sccb, code);
 
     cpu_physical_memory_write(sccb, &work_sccb,
                               be16_to_cpu(work_sccb.h.length));
 
-    sclp_service_interrupt(sccb);
+    sclp_c->service_interrupt(sclp, sccb);
 
 out:
     return r;
 }
 
-void sclp_service_interrupt(uint32_t sccb)
+static void service_interrupt(SCLPDevice *sclp, uint32_t sccb)
 {
-    SCLPEventFacility *ef = get_event_facility();
+    SCLPEventFacility *ef = sclp->event_facility;
     SCLPEventFacilityClass *efc = EVENT_FACILITY_GET_CLASS(ef);
 
     uint32_t param = sccb & ~3;
@@ -428,17 +431,148 @@ void sclp_service_interrupt(uint32_t sccb)
     s390_sclp_extint(param);
 }
 
+void sclp_service_interrupt(uint32_t sccb)
+{
+    SCLPDevice *sclp = get_sclp_device();
+    SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
+
+    sclp_c->service_interrupt(sclp, sccb);
+}
+
 /* qemu object creation and initialization functions */
 
 void s390_sclp_init(void)
 {
-    DeviceState *dev  = qdev_create(NULL, TYPE_SCLP_EVENT_FACILITY);
+    Object *new = object_new(TYPE_SCLP);
 
-    object_property_add_child(qdev_get_machine(), TYPE_SCLP_EVENT_FACILITY,
-                              OBJECT(dev), NULL);
-    qdev_init_nofail(dev);
+    object_property_add_child(qdev_get_machine(), TYPE_SCLP, new,
+                              NULL);
+    object_unref(OBJECT(new));
+    qdev_init_nofail(DEVICE(new));
+}
+
+static void sclp_realize(DeviceState *dev, Error **errp)
+{
+    MachineState *machine = MACHINE(qdev_get_machine());
+    SCLPDevice *sclp = SCLP(dev);
+    Error *l_err = NULL;
+    uint64_t hw_limit;
+    int ret;
+
+    object_property_set_bool(OBJECT(sclp->event_facility), true, "realized",
+                             &l_err);
+    if (l_err) {
+        goto error;
+    }
+
+    ret = s390_set_memory_limit(machine->maxram_size, &hw_limit);
+    if (ret == -E2BIG) {
+        error_setg(&l_err, "qemu: host supports a maximum of %" PRIu64 " GB",
+                   hw_limit >> 30);
+        goto error;
+    } else if (ret) {
+        error_setg(&l_err, "qemu: setting the guest size failed");
+        goto error;
+    }
+    return;
+error:
+    assert(l_err);
+    error_propagate(errp, l_err);
+}
+
+static void sclp_memory_init(SCLPDevice *sclp)
+{
+    MachineState *machine = MACHINE(qdev_get_machine());
+    ram_addr_t initial_mem = machine->ram_size;
+    ram_addr_t max_mem = machine->maxram_size;
+    ram_addr_t standby_mem = max_mem - initial_mem;
+    ram_addr_t pad_mem = 0;
+    int increment_size = 20;
+
+    /* The storage increment size is a multiple of 1M and is a power of 2.
+     * The number of storage increments must be MAX_STORAGE_INCREMENTS or fewer.
+     * The variable 'increment_size' is an exponent of 2 that can be
+     * used to calculate the size (in bytes) of an increment. */
+    while ((initial_mem >> increment_size) > MAX_STORAGE_INCREMENTS) {
+        increment_size++;
+    }
+    if (machine->ram_slots) {
+        while ((standby_mem >> increment_size) > MAX_STORAGE_INCREMENTS) {
+            increment_size++;
+        }
+    }
+    sclp->increment_size = increment_size;
+
+    /* The core and standby memory areas need to be aligned with
+     * the increment size.  In effect, this can cause the
+     * user-specified memory size to be rounded down to align
+     * with the nearest increment boundary. */
+    initial_mem = initial_mem >> increment_size << increment_size;
+    standby_mem = standby_mem >> increment_size << increment_size;
+
+    /* If the size of ram is not on a MEM_SECTION_SIZE boundary,
+       calculate the pad size necessary to force this boundary. */
+    if (machine->ram_slots && standby_mem) {
+        sclpMemoryHotplugDev *mhd = init_sclp_memory_hotplug_dev();
+
+        if (initial_mem % MEM_SECTION_SIZE) {
+            pad_mem = MEM_SECTION_SIZE - initial_mem % MEM_SECTION_SIZE;
+        }
+        mhd->increment_size = increment_size;
+        mhd->pad_size = pad_mem;
+        mhd->standby_mem_size = standby_mem;
+    }
+    machine->ram_size = initial_mem;
+    machine->maxram_size = initial_mem + pad_mem + standby_mem;
+    /* let's propagate the changed ram size into the global variable. */
+    ram_size = initial_mem;
+}
+
+static void sclp_init(Object *obj)
+{
+    SCLPDevice *sclp = SCLP(obj);
+    Object *new;
+
+    new = object_new(TYPE_SCLP_EVENT_FACILITY);
+    object_property_add_child(obj, TYPE_SCLP_EVENT_FACILITY, new, NULL);
+    /* qdev_device_add searches the sysbus for TYPE_SCLP_EVENTS_BUS */
+    qdev_set_parent_bus(DEVICE(new), sysbus_get_default());
+    object_unref(new);
+    sclp->event_facility = EVENT_FACILITY(new);
+
+    sclp_memory_init(sclp);
 }
 
+static void sclp_class_init(ObjectClass *oc, void *data)
+{
+    SCLPDeviceClass *sc = SCLP_CLASS(oc);
+    DeviceClass *dc = DEVICE_CLASS(oc);
+
+    dc->desc = "SCLP (Service-Call Logical Processor)";
+    dc->realize = sclp_realize;
+    dc->hotpluggable = false;
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+
+    sc->read_SCP_info = read_SCP_info;
+    sc->read_storage_element0_info = read_storage_element0_info;
+    sc->read_storage_element1_info = read_storage_element1_info;
+    sc->attach_storage_element = attach_storage_element;
+    sc->assign_storage = assign_storage;
+    sc->unassign_storage = unassign_storage;
+    sc->read_cpu_info = sclp_read_cpu_info;
+    sc->execute = sclp_execute;
+    sc->service_interrupt = service_interrupt;
+}
+
+static TypeInfo sclp_info = {
+    .name = TYPE_SCLP,
+    .parent = TYPE_DEVICE,
+    .instance_init = sclp_init,
+    .instance_size = sizeof(SCLPDevice),
+    .class_init = sclp_class_init,
+    .class_size = sizeof(SCLPDeviceClass),
+};
+
 sclpMemoryHotplugDev *init_sclp_memory_hotplug_dev(void)
 {
     DeviceState *dev;
@@ -475,5 +609,6 @@ static TypeInfo sclp_memory_hotplug_dev_info = {
 static void register_types(void)
 {
     type_register_static(&sclp_memory_hotplug_dev_info);
+    type_register_static(&sclp_info);
 }
 type_init(register_types);
diff --git a/hw/s390x/sclpcpu.c b/hw/s390x/sclpcpu.c
index 2fe8b5aa40..322eb31d95 100644
--- a/hw/s390x/sclpcpu.c
+++ b/hw/s390x/sclpcpu.c
@@ -25,13 +25,16 @@ typedef struct ConfigMgtData {
     uint8_t event_qualifier;
 } QEMU_PACKED ConfigMgtData;
 
-static qemu_irq *irq_cpu_hotplug; /* Only used in this file */
-
 #define EVENT_QUAL_CPU_CHANGE  1
 
 void raise_irq_cpu_hotplug(void)
 {
-    qemu_irq_raise(*irq_cpu_hotplug);
+    Object *obj = object_resolve_path_type("", TYPE_SCLP_CPU_HOTPLUG, NULL);
+
+    SCLP_EVENT(obj)->event_pending = true;
+
+    /* Trigger SCLP read operation */
+    sclp_service_interrupt(0);
 }
 
 static unsigned int send_mask(void)
@@ -70,36 +73,19 @@ static int read_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr,
     return 1;
 }
 
-static void trigger_signal(void *opaque, int n, int level)
-{
-    SCLPEvent *event = opaque;
-    event->event_pending = true;
-
-    /* Trigger SCLP read operation */
-    sclp_service_interrupt(0);
-}
-
-static int irq_cpu_hotplug_init(SCLPEvent *event)
-{
-    irq_cpu_hotplug = qemu_allocate_irqs(trigger_signal, event, 1);
-    return 0;
-}
-
 static void cpu_class_init(ObjectClass *oc, void *data)
 {
     SCLPEventClass *k = SCLP_EVENT_CLASS(oc);
     DeviceClass *dc = DEVICE_CLASS(oc);
 
-    k->init = irq_cpu_hotplug_init;
     k->get_send_mask = send_mask;
     k->get_receive_mask = receive_mask;
     k->read_event_data = read_event_data;
-    k->write_event_data = NULL;
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
 }
 
 static const TypeInfo sclp_cpu_info = {
-    .name          = "sclp-cpu-hotplug",
+    .name          = TYPE_SCLP_CPU_HOTPLUG,
     .parent        = TYPE_SCLP_EVENT,
     .instance_size = sizeof(SCLPEvent),
     .class_init    = cpu_class_init,
diff --git a/hw/s390x/sclpquiesce.c b/hw/s390x/sclpquiesce.c
index ffa5553135..15b06e108b 100644
--- a/hw/s390x/sclpquiesce.c
+++ b/hw/s390x/sclpquiesce.c
@@ -66,7 +66,7 @@ static int read_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr,
 }
 
 static const VMStateDescription vmstate_sclpquiesce = {
-    .name = "sclpquiesce",
+    .name = TYPE_SCLP_QUIESCE,
     .version_id = 0,
     .minimum_version_id = 0,
     .fields = (VMStateField[]) {
@@ -127,7 +127,7 @@ static void quiesce_class_init(ObjectClass *klass, void *data)
 }
 
 static const TypeInfo sclp_quiesce_info = {
-    .name          = "sclpquiesce",
+    .name          = TYPE_SCLP_QUIESCE,
     .parent        = TYPE_SCLP_EVENT,
     .instance_size = sizeof(SCLPEvent),
     .class_init    = quiesce_class_init,
diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h
index 6a062b668a..dd8881838c 100644
--- a/include/hw/s390x/event-facility.h
+++ b/include/hw/s390x/event-facility.h
@@ -47,6 +47,7 @@
      OBJECT_GET_CLASS(SCLPEventClass, (obj), TYPE_SCLP_EVENT)
 
 #define TYPE_SCLP_CPU_HOTPLUG "sclp-cpu-hotplug"
+#define TYPE_SCLP_QUIESCE "sclpquiesce"
 
 typedef struct WriteEventMask {
     SCCBHeader h;
@@ -146,8 +147,10 @@ typedef struct WriteEventData {
 
 typedef struct ReadEventData {
     SCCBHeader h;
-    EventBufferHeader ebh;
-    uint32_t mask;
+    union {
+        uint32_t mask;
+        EventBufferHeader ebh;
+    };
 } QEMU_PACKED ReadEventData;
 
 typedef struct SCLPEvent {
@@ -186,11 +189,8 @@ typedef struct SCLPEventClass {
      OBJECT_GET_CLASS(SCLPEventFacilityClass, (obj), \
                       TYPE_SCLP_EVENT_FACILITY)
 
-typedef struct SCLPEventFacility SCLPEventFacility;
-
 typedef struct SCLPEventFacilityClass {
-    DeviceClass parent_class;
-    int (*init)(SCLPEventFacility *ef);
+    SysBusDeviceClass parent_class;
     void (*command_handler)(SCLPEventFacility *ef, SCCB *sccb, uint64_t code);
     bool (*event_pending)(SCLPEventFacility *ef);
 } SCLPEventFacilityClass;
diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
index e8a64e25b7..b0c71b5550 100644
--- a/include/hw/s390x/sclp.h
+++ b/include/hw/s390x/sclp.h
@@ -163,6 +163,39 @@ typedef struct SCCB {
     char data[SCCB_DATA_LEN];
  } QEMU_PACKED SCCB;
 
+#define TYPE_SCLP "sclp"
+#define SCLP(obj) OBJECT_CHECK(SCLPDevice, (obj), TYPE_SCLP)
+#define SCLP_CLASS(oc) OBJECT_CLASS_CHECK(SCLPDeviceClass, (oc), TYPE_SCLP)
+#define SCLP_GET_CLASS(obj) OBJECT_GET_CLASS(SCLPDeviceClass, (obj), TYPE_SCLP)
+
+typedef struct SCLPEventFacility SCLPEventFacility;
+
+typedef struct SCLPDevice {
+    /* private */
+    DeviceState parent_obj;
+    SCLPEventFacility *event_facility;
+    int increment_size;
+
+    /* public */
+} SCLPDevice;
+
+typedef struct SCLPDeviceClass {
+    /* private */
+    DeviceClass parent_class;
+    void (*read_SCP_info)(SCLPDevice *sclp, SCCB *sccb);
+    void (*read_storage_element0_info)(SCLPDevice *sclp, SCCB *sccb);
+    void (*read_storage_element1_info)(SCLPDevice *sclp, SCCB *sccb);
+    void (*attach_storage_element)(SCLPDevice *sclp, SCCB *sccb,
+                                   uint16_t element);
+    void (*assign_storage)(SCLPDevice *sclp, SCCB *sccb);
+    void (*unassign_storage)(SCLPDevice *sclp, SCCB *sccb);
+    void (*read_cpu_info)(SCLPDevice *sclp, SCCB *sccb);
+
+    /* public */
+    void (*execute)(SCLPDevice *sclp, SCCB *sccb, uint32_t code);
+    void (*service_interrupt)(SCLPDevice *sclp, uint32_t sccb);
+} SCLPDeviceClass;
+
 typedef struct sclpMemoryHotplugDev sclpMemoryHotplugDev;
 
 #define TYPE_SCLP_MEMORY_HOTPLUG_DEV "sclp-memory-hotplug-dev"
diff --git a/kvm-all.c b/kvm-all.c
index 06e06f2b3f..c6f5128756 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1293,7 +1293,6 @@ int kvm_irqchip_add_adapter_route(KVMState *s, AdapterInfo *adapter)
     kroute.u.adapter.adapter_id = adapter->adapter_id;
 
     kvm_add_routing_entry(s, &kroute);
-    kvm_irqchip_commit_routes(s);
 
     return virq;
 }
diff --git a/pc-bios/s390-ccw.img b/pc-bios/s390-ccw.img
index f64380a972..0c540a10cf 100644
--- a/pc-bios/s390-ccw.img
+++ b/pc-bios/s390-ccw.img
diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
index 584d4a2769..d5fe4cea1d 100644
--- a/pc-bios/s390-ccw/main.c
+++ b/pc-bios/s390-ccw/main.c
@@ -38,40 +38,56 @@ void virtio_panic(const char *string)
     while (1) { }
 }
 
+static bool find_dev(struct schib *schib, int dev_no)
+{
+    int i, r;
+
+    for (i = 0; i < 0x10000; i++) {
+        blk_schid.sch_no = i;
+        r = stsch_err(blk_schid, schib);
+        if ((r == 3) || (r == -EIO)) {
+            break;
+        }
+        if (!schib->pmcw.dnv) {
+            continue;
+        }
+        if (!virtio_is_blk(blk_schid)) {
+            continue;
+        }
+        if ((dev_no < 0) || (schib->pmcw.dev == dev_no)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 static void virtio_setup(uint64_t dev_info)
 {
     struct schib schib;
-    int i;
-    int r;
+    int ssid;
     bool found = false;
-    bool check_devno = false;
-    uint16_t dev_no = -1;
+    uint16_t dev_no;
+
+    /*
+     * We unconditionally enable mss support. In every sane configuration,
+     * this will succeed; and even if it doesn't, stsch_err() can deal
+     * with the consequences.
+     */
+    enable_mss_facility();
 
     if (dev_info != -1) {
-        check_devno = true;
         dev_no = dev_info & 0xffff;
         debug_print_int("device no. ", dev_no);
         blk_schid.ssid = (dev_info >> 16) & 0x3;
-        if (blk_schid.ssid != 0) {
-            debug_print_int("ssid ", blk_schid.ssid);
-            if (enable_mss_facility() != 0) {
-                virtio_panic("Failed to enable mss facility\n");
-            }
-        }
-    }
-
-    for (i = 0; i < 0x10000; i++) {
-        blk_schid.sch_no = i;
-        r = stsch_err(blk_schid, &schib);
-        if (r == 3) {
-            break;
-        }
-        if (schib.pmcw.dnv) {
-            if (!check_devno || (schib.pmcw.dev == dev_no)) {
-                if (virtio_is_blk(blk_schid)) {
-                    found = true;
-                    break;
-                }
+        debug_print_int("ssid ", blk_schid.ssid);
+        found = find_dev(&schib, dev_no);
+    } else {
+        for (ssid = 0; ssid < 0x3; ssid++) {
+            blk_schid.ssid = ssid;
+            found = find_dev(&schib, -1);
+            if (found) {
+                break;
             }
         }
     }
diff --git a/target-s390x/gdbstub.c b/target-s390x/gdbstub.c
index 31f204964f..0c39a3c69f 100644
--- a/target-s390x/gdbstub.c
+++ b/target-s390x/gdbstub.c
@@ -174,6 +174,39 @@ static int cpu_write_vreg(CPUS390XState *env, uint8_t *mem_buf, int n)
     }
 }
 
+/* the values represent the positions in s390-cr.xml */
+#define S390_C0_REGNUM 0
+#define S390_C15_REGNUM 15
+/* total number of registers in s390-cr.xml */
+#define S390_NUM_C_REGS 16
+
+#ifndef CONFIG_USER_ONLY
+static int cpu_read_c_reg(CPUS390XState *env, uint8_t *mem_buf, int n)
+{
+    switch (n) {
+    case S390_C0_REGNUM ... S390_C15_REGNUM:
+        return gdb_get_regl(mem_buf, env->cregs[n]);
+    default:
+        return 0;
+    }
+}
+
+static int cpu_write_c_reg(CPUS390XState *env, uint8_t *mem_buf, int n)
+{
+    switch (n) {
+    case S390_C0_REGNUM ... S390_C15_REGNUM:
+        env->cregs[n] = ldtul_p(mem_buf);
+        if (tcg_enabled()) {
+            tlb_flush(ENV_GET_CPU(env), 1);
+        }
+        cpu_synchronize_post_init(ENV_GET_CPU(env));
+        return 8;
+    default:
+        return 0;
+    }
+}
+#endif
+
 void s390_cpu_gdb_init(CPUState *cs)
 {
     gdb_register_coprocessor(cs, cpu_read_ac_reg,
@@ -187,4 +220,10 @@ void s390_cpu_gdb_init(CPUState *cs)
     gdb_register_coprocessor(cs, cpu_read_vreg,
                              cpu_write_vreg,
                              S390_NUM_VREGS, "s390-vx.xml", 0);
+
+#ifndef CONFIG_USER_ONLY
+    gdb_register_coprocessor(cs, cpu_read_c_reg,
+                             cpu_write_c_reg,
+                             S390_NUM_C_REGS, "s390-cr.xml", 0);
+#endif
 }