Merge tag 's390-ccw-bios-2019-04-12' into s390-next-staging

Support for booting from a vfio-ccw passthrough dasd device

# gpg: Signature made Fri 12 Apr 2019 01:17:03 PM CEST
# gpg:                using RSA key 2ED9D774FE702DB5
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [undefined]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [undefined]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]

* tag 's390-ccw-bios-2019-04-12':
  pc-bios/s390: Update firmware images
  s390-bios: Use control unit type to find bootable devices
  s390-bios: Support booting from real dasd device
  s390-bios: Add channel command codes/structs needed for dasd-ipl
  s390-bios: Use control unit type to determine boot method
  s390-bios: Refactor virtio to run channel programs via cio
  s390-bios: Factor finding boot device out of virtio code path
  s390-bios: Extend find_dev() for non-virtio devices
  s390-bios: cio error handling
  s390-bios: Support for running format-0/1 channel programs
  s390-bios: ptr2u32 and u32toptr
  s390-bios: Map low core memory
  s390-bios: Decouple channel i/o logic from virtio
  s390-bios: Clean up cio.h
  s390-bios: decouple common boot logic from virtio
  s390-bios: decouple cio setup from virtio
  s390 vfio-ccw: Add bootindex property and IPLB data

Signed-off-by: Cornelia Huck <cohuck@redhat.com>

24 files changed, 1446 insertions, 201 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 23db6f8..dabbfcc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1181,6 +1181,7 @@ S: Supported
 F: hw/s390x/ipl.*
 F: pc-bios/s390-ccw/
 F: pc-bios/s390-ccw.img
+F: docs/devel/s390-dasd-ipl.txt
 T: git https://github.com/borntraeger/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
@@ -1445,6 +1446,7 @@ S: Supported
 F: hw/vfio/ccw.c
 F: hw/s390x/s390-ccw.c
 F: include/hw/s390x/s390-ccw.h
+F: include/hw/s390x/vfio-ccw.h
 T: git https://github.com/cohuck/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
diff --git a/docs/devel/s390-dasd-ipl.txt b/docs/devel/s390-dasd-ipl.txt
new file mode 100644
index 0000000..9107e04
--- /dev/null
+++ b/docs/devel/s390-dasd-ipl.txt
@@ -0,0 +1,133 @@
+*****************************
+***** s390 hardware IPL *****
+*****************************
+
+The s390 hardware IPL process consists of the following steps.
+
+1. A READ IPL ccw is constructed in memory location 0x0.
+    This ccw, by definition, reads the IPL1 record which is located on the disk
+    at cylinder 0 track 0 record 1. Note that the chain flag is on in this ccw
+    so when it is complete another ccw will be fetched and executed from memory
+    location 0x08.
+
+2. Execute the Read IPL ccw at 0x00, thereby reading IPL1 data into 0x00.
+    IPL1 data is 24 bytes in length and consists of the following pieces of
+    information: [psw][read ccw][tic ccw]. When the machine executes the Read
+    IPL ccw it read the 24-bytes of IPL1 to be read into memory starting at
+    location 0x0. Then the ccw program at 0x08 which consists of a read
+    ccw and a tic ccw is automatically executed because of the chain flag from
+    the original READ IPL ccw. The read ccw will read the IPL2 data into memory
+    and the TIC (Transfer In Channel) will transfer control to the channel
+    program contained in the IPL2 data. The TIC channel command is the
+    equivalent of a branch/jump/goto instruction for channel programs.
+    NOTE: The ccws in IPL1 are defined by the architecture to be format 0.
+
+3. Execute IPL2.
+    The TIC ccw instruction at the end of the IPL1 channel program will begin
+    the execution of the IPL2 channel program. IPL2 is stage-2 of the boot
+    process and will contain a larger channel program than IPL1. The point of
+    IPL2 is to find and load either the operating system or a small program that
+    loads the operating system from disk. At the end of this step all or some of
+    the real operating system is loaded into memory and we are ready to hand
+    control over to the guest operating system. At this point the guest
+    operating system is entirely responsible for loading any more data it might
+    need to function. NOTE: The IPL2 channel program might read data into memory
+    location 0 thereby overwriting the IPL1 psw and channel program. This is ok
+    as long as the data placed in location 0 contains a psw whose instruction
+    address points to the guest operating system code to execute at the end of
+    the IPL/boot process.
+    NOTE: The ccws in IPL2 are defined by the architecture to be format 0.
+
+4. Start executing the guest operating system.
+    The psw that was loaded into memory location 0 as part of the ipl process
+    should contain the needed flags for the operating system we have loaded. The
+    psw's instruction address will point to the location in memory where we want
+    to start executing the operating system. This psw is loaded (via LPSW
+    instruction) causing control to be passed to the operating system code.
+
+In a non-virtualized environment this process, handled entirely by the hardware,
+is kicked off by the user initiating a "Load" procedure from the hardware
+management console. This "Load" procedure crafts a special "Read IPL" ccw in
+memory location 0x0 that reads IPL1. It then executes this ccw thereby kicking
+off the reading of IPL1 data. Since the channel program from IPL1 will be
+written immediately after the special "Read IPL" ccw, the IPL1 channel program
+will be executed immediately (the special read ccw has the chaining bit turned
+on). The TIC at the end of the IPL1 channel program will cause the IPL2 channel
+program to be executed automatically. After this sequence completes the "Load"
+procedure then loads the psw from 0x0.
+
+**********************************************************
+***** How this all pertains to QEMU (and the kernel) *****
+**********************************************************
+
+In theory we should merely have to do the following to IPL/boot a guest
+operating system from a DASD device:
+
+1. Place a "Read IPL" ccw into memory location 0x0 with chaining bit on.
+2. Execute channel program at 0x0.
+3. LPSW 0x0.
+
+However, our emulation of the machine's channel program logic within the kernel
+is missing one key feature that is required for this process to work:
+non-prefetch of ccw data.
+
+When we start a channel program we pass the channel subsystem parameters via an
+ORB (Operation Request Block). One of those parameters is a prefetch bit. If the
+bit is on then the vfio-ccw kernel driver is allowed to read the entire channel
+program from guest memory before it starts executing it. This means that any
+channel commands that read additional channel commands will not work as expected
+because the newly read commands will only exist in guest memory and NOT within
+the kernel's channel subsystem memory. The kernel vfio-ccw driver currently
+requires this bit to be on for all channel programs. This is a problem because
+the IPL process consists of transferring control from the "Read IPL" ccw
+immediately to the IPL1 channel program that was read by "Read IPL".
+
+Not being able to turn off prefetch will also prevent the TIC at the end of the
+IPL1 channel program from transferring control to the IPL2 channel program.
+
+Lastly, in some cases (the zipl bootloader for example) the IPL2 program also
+transfers control to another channel program segment immediately after reading
+it from the disk. So we need to be able to handle this case.
+
+**************************
+***** What QEMU does *****
+**************************
+
+Since we are forced to live with prefetch we cannot use the very simple IPL
+procedure we defined in the preceding section. So we compensate by doing the
+following.
+
+1. Place "Read IPL" ccw into memory location 0x0, but turn off chaining bit.
+2. Execute "Read IPL" at 0x0.
+
+   So now IPL1's psw is at 0x0 and IPL1's channel program is at 0x08.
+
+4. Write a custom channel program that will seek to the IPL2 record and then
+   execute the READ and TIC ccws from IPL1.  Normally the seek is not required
+   because after reading the IPL1 record the disk is automatically positioned
+   to read the very next record which will be IPL2. But since we are not reading
+   both IPL1 and IPL2 as part of the same channel program we must manually set
+   the position.
+
+5. Grab the target address of the TIC instruction from the IPL1 channel program.
+   This address is where the IPL2 channel program starts.
+
+   Now IPL2 is loaded into memory somewhere, and we know the address.
+
+6. Execute the IPL2 channel program at the address obtained in step #5.
+
+   Because this channel program can be dynamic, we must use a special algorithm
+   that detects a READ immediately followed by a TIC and breaks the ccw chain
+   by turning off the chain bit in the READ ccw. When control is returned from
+   the kernel/hardware to the QEMU bios code we immediately issue another start
+   subchannel to execute the remaining TIC instruction. This causes the entire
+   channel program (starting from the TIC) and all needed data to be refetched
+   thereby stepping around the limitation that would otherwise prevent this
+   channel program from executing properly.
+
+   Now the operating system code is loaded somewhere in guest memory and the psw
+   in memory location 0x0 will point to entry code for the guest operating
+   system.
+
+7. LPSW 0x0.
+   LPSW transfers control to the guest operating system and we're done.
diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 51b272e..d0cc06a 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -19,6 +19,7 @@
 #include "hw/loader.h"
 #include "hw/boards.h"
 #include "hw/s390x/virtio-ccw.h"
+#include "hw/s390x/vfio-ccw.h"
 #include "hw/s390x/css.h"
 #include "hw/s390x/ebcdic.h"
 #include "ipl.h"
@@ -303,16 +304,36 @@ static void s390_ipl_set_boot_menu(S390IPLState *ipl)
     ipl->qipl.boot_menu_timeout = cpu_to_be32(splash_time);
 }
 
-static CcwDevice *s390_get_ccw_device(DeviceState *dev_st)
+#define CCW_DEVTYPE_NONE        0x00
+#define CCW_DEVTYPE_VIRTIO      0x01
+#define CCW_DEVTYPE_VIRTIO_NET  0x02
+#define CCW_DEVTYPE_SCSI        0x03
+#define CCW_DEVTYPE_VFIO        0x04
+
+static CcwDevice *s390_get_ccw_device(DeviceState *dev_st, int *devtype)
 {
     CcwDevice *ccw_dev = NULL;
+    int tmp_dt = CCW_DEVTYPE_NONE;
 
     if (dev_st) {
+        VirtIONet *virtio_net_dev = (VirtIONet *)
+            object_dynamic_cast(OBJECT(dev_st), TYPE_VIRTIO_NET);
         VirtioCcwDevice *virtio_ccw_dev = (VirtioCcwDevice *)
             object_dynamic_cast(OBJECT(qdev_get_parent_bus(dev_st)->parent),
                                 TYPE_VIRTIO_CCW_DEVICE);
+        VFIOCCWDevice *vfio_ccw_dev = (VFIOCCWDevice *)
+            object_dynamic_cast(OBJECT(dev_st), TYPE_VFIO_CCW);
+
         if (virtio_ccw_dev) {
             ccw_dev = CCW_DEVICE(virtio_ccw_dev);
+            if (virtio_net_dev) {
+                tmp_dt = CCW_DEVTYPE_VIRTIO_NET;
+            } else {
+                tmp_dt = CCW_DEVTYPE_VIRTIO;
+            }
+        } else if (vfio_ccw_dev) {
+            ccw_dev = CCW_DEVICE(vfio_ccw_dev);
+            tmp_dt = CCW_DEVTYPE_VFIO;
         } else {
             SCSIDevice *sd = (SCSIDevice *)
                 object_dynamic_cast(OBJECT(dev_st),
@@ -325,9 +346,13 @@ static CcwDevice *s390_get_ccw_device(DeviceState *dev_st)
 
                 ccw_dev = (CcwDevice *)object_dynamic_cast(OBJECT(scsi_ccw),
                                                            TYPE_CCW_DEVICE);
+                tmp_dt = CCW_DEVTYPE_SCSI;
             }
         }
     }
+    if (devtype) {
+        *devtype = tmp_dt;
+    }
     return ccw_dev;
 }
 
@@ -335,20 +360,22 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
 {
     DeviceState *dev_st;
     CcwDevice *ccw_dev = NULL;
+    SCSIDevice *sd;
+    int devtype;
 
     dev_st = get_boot_device(0);
     if (dev_st) {
-        ccw_dev = s390_get_ccw_device(dev_st);
+        ccw_dev = s390_get_ccw_device(dev_st, &devtype);
     }
 
     /*
      * Currently allow IPL only from CCW devices.
      */
     if (ccw_dev) {
-        SCSIDevice *sd = (SCSIDevice *) object_dynamic_cast(OBJECT(dev_st),
-                                                            TYPE_SCSI_DEVICE);
-
-        if (sd) {
+        switch (devtype) {
+        case CCW_DEVTYPE_SCSI:
+            sd = (SCSIDevice *) object_dynamic_cast(OBJECT(dev_st),
+                                                           TYPE_SCSI_DEVICE);
             ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN);
             ipl->iplb.blk0_len =
                 cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN - S390_IPLB_HEADER_LEN);
@@ -358,20 +385,24 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
             ipl->iplb.scsi.channel = cpu_to_be16(sd->channel);
             ipl->iplb.scsi.devno = cpu_to_be16(ccw_dev->sch->devno);
             ipl->iplb.scsi.ssid = ccw_dev->sch->ssid & 3;
-        } else {
-            VirtIONet *vn = (VirtIONet *) object_dynamic_cast(OBJECT(dev_st),
-                                                              TYPE_VIRTIO_NET);
-
+            break;
+        case CCW_DEVTYPE_VFIO:
+            ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
+            ipl->iplb.pbt = S390_IPL_TYPE_CCW;
+            ipl->iplb.ccw.devno = cpu_to_be16(ccw_dev->sch->devno);
+            ipl->iplb.ccw.ssid = ccw_dev->sch->ssid & 3;
+            break;
+        case CCW_DEVTYPE_VIRTIO_NET:
+            ipl->netboot = true;
+            /* Fall through to CCW_DEVTYPE_VIRTIO case */
+        case CCW_DEVTYPE_VIRTIO:
             ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
             ipl->iplb.blk0_len =
                 cpu_to_be32(S390_IPLB_MIN_CCW_LEN - S390_IPLB_HEADER_LEN);
             ipl->iplb.pbt = S390_IPL_TYPE_CCW;
             ipl->iplb.ccw.devno = cpu_to_be16(ccw_dev->sch->devno);
             ipl->iplb.ccw.ssid = ccw_dev->sch->ssid & 3;
-
-            if (vn) {
-                ipl->netboot = true;
-            }
+            break;
         }
 
         if (!s390_ipl_set_loadparm(ipl->iplb.loadparm)) {
@@ -530,7 +561,7 @@ void s390_ipl_reset_request(CPUState *cs, enum s390_reset reset_type)
         !ipl->netboot &&
         ipl->iplb.pbt == S390_IPL_TYPE_CCW &&
         is_virtio_scsi_device(&ipl->iplb)) {
-        CcwDevice *ccw_dev = s390_get_ccw_device(get_boot_device(0));
+        CcwDevice *ccw_dev = s390_get_ccw_device(get_boot_device(0), NULL);
 
         if (ccw_dev &&
             cpu_to_be16(ccw_dev->sch->devno) == ipl->iplb.ccw.devno &&
diff --git a/hw/s390x/s390-ccw.c b/hw/s390x/s390-ccw.c
index cad91ee..f5f025d 100644
--- a/hw/s390x/s390-ccw.c
+++ b/hw/s390x/s390-ccw.c
@@ -124,6 +124,14 @@ static void s390_ccw_unrealize(S390CCWDevice *cdev, Error **errp)
     g_free(cdev->mdevid);
 }
 
+static void s390_ccw_instance_init(Object *obj)
+{
+    S390CCWDevice *dev = S390_CCW_DEVICE(obj);
+
+    device_add_bootindex_property(obj, &dev->bootindex, "bootindex",
+                                  "/disk@0,0", DEVICE(obj), NULL);
+}
+
 static void s390_ccw_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -137,6 +145,7 @@ static void s390_ccw_class_init(ObjectClass *klass, void *data)
 static const TypeInfo s390_ccw_info = {
     .name          = TYPE_S390_CCW,
     .parent        = TYPE_CCW_DEVICE,
+    .instance_init = s390_ccw_instance_init,
     .instance_size = sizeof(S390CCWDevice),
     .class_size    = sizeof(S390CCWDeviceClass),
     .class_init    = s390_ccw_class_init,
diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index c44d13c..31dd3a2 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -21,12 +21,12 @@
 #include "hw/vfio/vfio.h"
 #include "hw/vfio/vfio-common.h"
 #include "hw/s390x/s390-ccw.h"
+#include "hw/s390x/vfio-ccw.h"
 #include "hw/s390x/ccw-device.h"
 #include "exec/address-spaces.h"
 #include "qemu/error-report.h"
 
-#define TYPE_VFIO_CCW "vfio-ccw"
-typedef struct VFIOCCWDevice {
+struct VFIOCCWDevice {
     S390CCWDevice cdev;
     VFIODevice vdev;
     uint64_t io_region_size;
@@ -35,7 +35,7 @@ typedef struct VFIOCCWDevice {
     EventNotifier io_notifier;
     bool force_orb_pfch;
     bool warned_orb_pfch;
-} VFIOCCWDevice;
+};
 
 static inline void warn_once_pfch(VFIOCCWDevice *vcdev, SubchDev *sch,
                                   const char *msg)
diff --git a/include/hw/s390x/s390-ccw.h b/include/hw/s390x/s390-ccw.h
index 7d15a1a..901d805 100644
--- a/include/hw/s390x/s390-ccw.h
+++ b/include/hw/s390x/s390-ccw.h
@@ -27,6 +27,7 @@ typedef struct S390CCWDevice {
     CcwDevice parent_obj;
     CssDevId hostid;
     char *mdevid;
+    int32_t bootindex;
 } S390CCWDevice;
 
 typedef struct S390CCWDeviceClass {
diff --git a/include/hw/s390x/vfio-ccw.h b/include/hw/s390x/vfio-ccw.h
new file mode 100644
index 0000000..ee5250d
--- /dev/null
+++ b/include/hw/s390x/vfio-ccw.h
@@ -0,0 +1,28 @@
+/*
+ * vfio based subchannel assignment support
+ *
+ * Copyright 2017, 2019 IBM Corp.
+ * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
+ *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
+ *            Pierre Morel <pmorel@linux.vnet.ibm.com>
+ *
+ * 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.
+ */
+
+#ifndef HW_VFIO_CCW_H
+#define HW_VFIO_CCW_H
+
+#include "hw/vfio/vfio-common.h"
+#include "hw/s390x/s390-ccw.h"
+#include "hw/s390x/ccw-device.h"
+
+#define TYPE_VFIO_CCW "vfio-ccw"
+#define VFIO_CCW(obj) \
+        OBJECT_CHECK(VFIOCCWDevice, (obj), TYPE_VFIO_CCW)
+
+#define TYPE_VFIO_CCW "vfio-ccw"
+typedef struct VFIOCCWDevice VFIOCCWDevice;
+
+#endif
diff --git a/pc-bios/s390-ccw.img b/pc-bios/s390-ccw.img
index 450a076..ba05482 100644
--- a/pc-bios/s390-ccw.img
+++ b/pc-bios/s390-ccw.img
diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
index 1eb316b..a048b6b 100644
--- a/pc-bios/s390-ccw/Makefile
+++ b/pc-bios/s390-ccw/Makefile
@@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \
-	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o
+	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o dasd-ipl.o
 
 QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
 QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
diff --git a/pc-bios/s390-ccw/cio.c b/pc-bios/s390-ccw/cio.c
new file mode 100644
index 0000000..339ec5f
--- /dev/null
+++ b/pc-bios/s390-ccw/cio.c
@@ -0,0 +1,423 @@
+/*
+ * S390 Channel I/O
+ *
+ * Copyright (c) 2013 Alexander Graf <agraf@suse.de>
+ * Copyright (c) 2019 IBM Corp.
+ *
+ * Author(s): Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * 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.
+ */
+
+#include "libc.h"
+#include "s390-ccw.h"
+#include "s390-arch.h"
+#include "helper.h"
+#include "cio.h"
+
+static char chsc_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
+
+static int __do_cio(SubChannelId schid, uint32_t ccw_addr, int fmt, Irb *irb);
+
+int enable_mss_facility(void)
+{
+    int ret;
+    ChscAreaSda *sda_area = (ChscAreaSda *) chsc_page;
+
+    memset(sda_area, 0, PAGE_SIZE);
+    sda_area->request.length = 0x0400;
+    sda_area->request.code = 0x0031;
+    sda_area->operation_code = 0x2;
+
+    ret = chsc(sda_area);
+    if ((ret == 0) && (sda_area->response.code == 0x0001)) {
+        return 0;
+    }
+    return -EIO;
+}
+
+void enable_subchannel(SubChannelId schid)
+{
+    Schib schib;
+
+    stsch_err(schid, &schib);
+    schib.pmcw.ena = 1;
+    msch(schid, &schib);
+}
+
+uint16_t cu_type(SubChannelId schid)
+{
+    Ccw1 sense_id_ccw;
+    SenseId sense_data;
+
+    sense_id_ccw.cmd_code = CCW_CMD_SENSE_ID;
+    sense_id_ccw.cda = ptr2u32(&sense_data);
+    sense_id_ccw.count = sizeof(sense_data);
+    sense_id_ccw.flags |= CCW_FLAG_SLI;
+
+    if (do_cio(schid, CU_TYPE_UNKNOWN, ptr2u32(&sense_id_ccw), CCW_FMT1)) {
+        panic("Failed to run SenseID CCw\n");
+    }
+
+    return sense_data.cu_type;
+}
+
+int basic_sense(SubChannelId schid, uint16_t cutype, void *sense_data,
+                 uint16_t data_size)
+{
+    Ccw1 senseCcw;
+    Irb irb;
+
+    senseCcw.cmd_code = CCW_CMD_BASIC_SENSE;
+    senseCcw.cda = ptr2u32(sense_data);
+    senseCcw.count = data_size;
+
+    return __do_cio(schid, ptr2u32(&senseCcw), CCW_FMT1, &irb);
+}
+
+static bool irb_error(Irb *irb)
+{
+    if (irb->scsw.cstat) {
+        return true;
+    }
+    return irb->scsw.dstat != (SCSW_DSTAT_DEVEND | SCSW_DSTAT_CHEND);
+}
+
+static void print_eckd_dasd_sense_data(SenseDataEckdDasd *sd)
+{
+    char msgline[512];
+
+    if (sd->config_info & 0x8000) {
+        sclp_print("Eckd Dasd Sense Data (fmt 24-bytes):\n");
+    } else {
+        sclp_print("Eckd Dasd Sense Data (fmt 32-bytes):\n");
+    }
+
+    strcat(msgline, "    Sense Condition Flags :");
+    if (sd->common_status & SNS_STAT0_CMD_REJECT) {
+        strcat(msgline, " [Cmd-Reject]");
+    }
+    if (sd->common_status & SNS_STAT0_INTERVENTION_REQ) {
+        strcat(msgline, " [Intervention-Required]");
+    }
+    if (sd->common_status & SNS_STAT0_BUS_OUT_CHECK) {
+        strcat(msgline, " [Bus-Out-Parity-Check]");
+    }
+    if (sd->common_status & SNS_STAT0_EQUIPMENT_CHECK) {
+        strcat(msgline, " [Equipment-Check]");
+    }
+    if (sd->common_status & SNS_STAT0_DATA_CHECK) {
+        strcat(msgline, " [Data-Check]");
+    }
+    if (sd->common_status & SNS_STAT0_OVERRUN) {
+        strcat(msgline, " [Overrun]");
+    }
+    if (sd->common_status & SNS_STAT0_INCOMPL_DOMAIN) {
+        strcat(msgline, " [Incomplete-Domain]");
+    }
+
+    if (sd->status[0] & SNS_STAT1_PERM_ERR) {
+        strcat(msgline, " [Permanent-Error]");
+    }
+    if (sd->status[0] & SNS_STAT1_INV_TRACK_FORMAT) {
+        strcat(msgline, " [Invalid-Track-Fmt]");
+    }
+    if (sd->status[0] & SNS_STAT1_EOC) {
+        strcat(msgline, " [End-of-Cyl]");
+    }
+    if (sd->status[0] & SNS_STAT1_MESSAGE_TO_OPER) {
+        strcat(msgline, " [Operator-Msg]");
+    }
+    if (sd->status[0] & SNS_STAT1_NO_REC_FOUND) {
+        strcat(msgline, " [No-Record-Found]");
+    }
+    if (sd->status[0] & SNS_STAT1_FILE_PROTECTED) {
+        strcat(msgline, " [File-Protected]");
+    }
+    if (sd->status[0] & SNS_STAT1_WRITE_INHIBITED) {
+        strcat(msgline, " [Write-Inhibited]");
+    }
+    if (sd->status[0] & SNS_STAT1_IMPRECISE_END) {
+        strcat(msgline, " [Imprecise-Ending]");
+    }
+
+    if (sd->status[1] & SNS_STAT2_REQ_INH_WRITE) {
+        strcat(msgline, " [Req-Inhibit-Write]");
+    }
+    if (sd->status[1] & SNS_STAT2_CORRECTABLE) {
+        strcat(msgline, " [Correctable-Data-Check]");
+    }
+    if (sd->status[1] & SNS_STAT2_FIRST_LOG_ERR) {
+        strcat(msgline, " [First-Error-Log]");
+    }
+    if (sd->status[1] & SNS_STAT2_ENV_DATA_PRESENT) {
+        strcat(msgline, " [Env-Data-Present]");
+    }
+    if (sd->status[1] & SNS_STAT2_IMPRECISE_END) {
+        strcat(msgline, " [Imprecise-End]");
+    }
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    print_int("    Residual Count     =", sd->res_count);
+    print_int("    Phys Drive ID      =", sd->phys_drive_id);
+    print_int("    low cyl address    =", sd->low_cyl_addr);
+    print_int("    head addr & hi cyl =", sd->head_high_cyl_addr);
+    print_int("    format/message     =", sd->fmt_msg);
+    print_int("    fmt-dependent[0-7] =", sd->fmt_dependent_info[0]);
+    print_int("    fmt-dependent[8-15]=", sd->fmt_dependent_info[1]);
+    print_int("    prog action code   =", sd->program_action_code);
+    print_int("    Configuration info =", sd->config_info);
+    print_int("    mcode / hi-cyl     =", sd->mcode_hicyl);
+    print_int("    cyl & head addr [0]=", sd->cyl_head_addr[0]);
+    print_int("    cyl & head addr [1]=", sd->cyl_head_addr[1]);
+    print_int("    cyl & head addr [2]=", sd->cyl_head_addr[2]);
+}
+
+static void print_irb_err(Irb *irb)
+{
+    uint64_t this_ccw = *(uint64_t *)u32toptr(irb->scsw.cpa);
+    uint64_t prev_ccw = *(uint64_t *)u32toptr(irb->scsw.cpa - 8);
+    char msgline[256];
+
+    sclp_print("Interrupt Response Block Data:\n");
+
+    strcat(msgline, "    Function Ctrl :");
+    if (irb->scsw.ctrl & SCSW_FCTL_START_FUNC) {
+        strcat(msgline, " [Start]");
+    }
+    if (irb->scsw.ctrl & SCSW_FCTL_HALT_FUNC) {
+        strcat(msgline, " [Halt]");
+    }
+    if (irb->scsw.ctrl & SCSW_FCTL_CLEAR_FUNC) {
+        strcat(msgline, " [Clear]");
+    }
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    msgline[0] = '\0';
+    strcat(msgline, "    Activity Ctrl :");
+    if (irb->scsw.ctrl & SCSW_ACTL_RESUME_PEND) {
+        strcat(msgline, " [Resume-Pending]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_START_PEND) {
+        strcat(msgline, " [Start-Pending]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_HALT_PEND) {
+        strcat(msgline, " [Halt-Pending]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_CLEAR_PEND) {
+        strcat(msgline, " [Clear-Pending]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_CH_ACTIVE) {
+        strcat(msgline, " [Channel-Active]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_DEV_ACTIVE) {
+        strcat(msgline, " [Device-Active]");
+    }
+    if (irb->scsw.ctrl & SCSW_ACTL_SUSPENDED) {
+        strcat(msgline, " [Suspended]");
+    }
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    msgline[0] = '\0';
+    strcat(msgline, "    Status Ctrl :");
+    if (irb->scsw.ctrl & SCSW_SCTL_ALERT) {
+        strcat(msgline, " [Alert]");
+    }
+    if (irb->scsw.ctrl & SCSW_SCTL_INTERMED) {
+        strcat(msgline, " [Intermediate]");
+    }
+    if (irb->scsw.ctrl & SCSW_SCTL_PRIMARY) {
+        strcat(msgline, " [Primary]");
+    }
+    if (irb->scsw.ctrl & SCSW_SCTL_SECONDARY) {
+        strcat(msgline, " [Secondary]");
+    }
+    if (irb->scsw.ctrl & SCSW_SCTL_STATUS_PEND) {
+        strcat(msgline, " [Status-Pending]");
+    }
+
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    msgline[0] = '\0';
+    strcat(msgline, "    Device Status :");
+    if (irb->scsw.dstat & SCSW_DSTAT_ATTN) {
+        strcat(msgline, " [Attention]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_STATMOD) {
+        strcat(msgline, " [Status-Modifier]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_CUEND) {
+        strcat(msgline, " [Ctrl-Unit-End]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_BUSY) {
+        strcat(msgline, " [Busy]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_CHEND) {
+        strcat(msgline, " [Channel-End]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_DEVEND) {
+        strcat(msgline, " [Device-End]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_UCHK) {
+        strcat(msgline, " [Unit-Check]");
+    }
+    if (irb->scsw.dstat & SCSW_DSTAT_UEXCP) {
+        strcat(msgline, " [Unit-Exception]");
+    }
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    msgline[0] = '\0';
+    strcat(msgline, "    Channel Status :");
+    if (irb->scsw.cstat & SCSW_CSTAT_PCINT) {
+        strcat(msgline, " [Program-Ctrl-Interruption]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_BADLEN) {
+        strcat(msgline, " [Incorrect-Length]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_PROGCHK) {
+        strcat(msgline, " [Program-Check]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_PROTCHK) {
+        strcat(msgline, " [Protection-Check]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_CHDCHK) {
+        strcat(msgline, " [Channel-Data-Check]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_CHCCHK) {
+        strcat(msgline, " [Channel-Ctrl-Check]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_ICCHK) {
+        strcat(msgline, " [Interface-Ctrl-Check]");
+    }
+    if (irb->scsw.cstat & SCSW_CSTAT_CHAINCHK) {
+        strcat(msgline, " [Chaining-Check]");
+    }
+    strcat(msgline, "\n");
+    sclp_print(msgline);
+
+    print_int("    cpa=", irb->scsw.cpa);
+    print_int("    prev_ccw=", prev_ccw);
+    print_int("    this_ccw=", this_ccw);
+}
+
+/*
+ * Handles executing ssch, tsch and returns the irb obtained from tsch.
+ * Returns 0 on success, -1 if unexpected status pending and we need to retry,
+ * otherwise returns condition code from ssch/tsch for error cases.
+ */
+static int __do_cio(SubChannelId schid, uint32_t ccw_addr, int fmt, Irb *irb)
+{
+    CmdOrb orb = {};
+    int rc;
+
+    IPL_assert(fmt == 0 || fmt == 1, "Invalid ccw format");
+
+    /* ccw_addr must be <= 24 bits and point to at least one whole ccw. */
+    if (fmt == 0) {
+        IPL_assert(ccw_addr <= 0xFFFFFF - 8, "Invalid ccw address");
+    }
+
+    orb.fmt = fmt;
+    orb.pfch = 1;  /* QEMU's cio implementation requires prefetch */
+    orb.c64 = 1;   /* QEMU's cio implementation requires 64-bit idaws */
+    orb.lpm = 0xFF; /* All paths allowed */
+    orb.cpa = ccw_addr;
+
+    rc = ssch(schid, &orb);
+    if (rc == 1 || rc == 2) {
+        /* Subchannel status pending or busy. Eat status and ask for retry. */
+        tsch(schid, irb);
+        return -1;
+    }
+    if (rc) {
+        print_int("ssch failed with cc=", rc);
+        return rc;
+    }
+
+    consume_io_int();
+
+    /* collect status */
+    rc = tsch(schid, irb);
+    if (rc) {
+        print_int("tsch failed with cc=", rc);
+    }
+
+    return rc;
+}
+
+/*
+ * Executes a channel program at a given subchannel. The request to run the
+ * channel program is sent to the subchannel, we then wait for the interrupt
+ * signaling completion of the I/O operation(s) performed by the channel
+ * program. Lastly we verify that the i/o operation completed without error and
+ * that the interrupt we received was for the subchannel used to run the
+ * channel program.
+ *
+ * Note: This function assumes it is running in an environment where no other
+ * cpus are generating or receiving I/O interrupts. So either run it in a
+ * single-cpu environment or make sure all other cpus are not doing I/O and
+ * have I/O interrupts masked off. We also assume that only one device is
+ * active (generating i/o interrupts).
+ *
+ * Returns non-zero on error.
+ */
+int do_cio(SubChannelId schid, uint16_t cutype, uint32_t ccw_addr, int fmt)
+{
+    Irb irb = {};
+    SenseDataEckdDasd sd;
+    int rc, retries = 0;
+
+    while (true) {
+        rc = __do_cio(schid, ccw_addr, fmt, &irb);
+
+        if (rc == -1) {
+            retries++;
+            continue;
+        }
+        if (rc) {
+            /* ssch/tsch error. Message already reported by __do_cio */
+            break;
+        }
+
+        if (!irb_error(&irb)) {
+            break;
+        }
+
+        /*
+         * Unexpected unit check, or interface-control-check. Use sense to
+         * clear (unit check only) then retry.
+         */
+        if ((unit_check(&irb) || iface_ctrl_check(&irb)) && retries <= 2) {
+            if (unit_check(&irb)) {
+                basic_sense(schid, cutype, &sd, sizeof(sd));
+            }
+            retries++;
+            continue;
+        }
+
+        sclp_print("cio device error\n");
+        print_int("  ssid  ", schid.ssid);
+        print_int("  cssid ", schid.cssid);
+        print_int("  sch_no", schid.sch_no);
+        print_int("  ctrl-unit type", cutype);
+        sclp_print("\n");
+        print_irb_err(&irb);
+        if (cutype == CU_TYPE_DASD_3990 || cutype == CU_TYPE_DASD_2107 ||
+            cutype == CU_TYPE_UNKNOWN) {
+            if (!basic_sense(schid, cutype, &sd, sizeof(sd))) {
+                print_eckd_dasd_sense_data(&sd);
+            }
+        }
+        rc = -1;
+        break;
+    }
+
+    return rc;
+}
diff --git a/pc-bios/s390-ccw/cio.h b/pc-bios/s390-ccw/cio.h
index 1a0795f..aaa432d 100644
--- a/pc-bios/s390-ccw/cio.h
+++ b/pc-bios/s390-ccw/cio.h
@@ -17,35 +17,35 @@
  * path management control word
  */
 struct pmcw {
-    __u32 intparm;        /* interruption parameter */
-    __u32 qf      : 1;    /* qdio facility */
-    __u32 w       : 1;
-    __u32 isc     : 3;    /* interruption sublass */
-    __u32 res5    : 3;    /* reserved zeros */
-    __u32 ena     : 1;    /* enabled */
-    __u32 lm      : 2;    /* limit mode */
-    __u32 mme     : 2;    /* measurement-mode enable */
-    __u32 mp      : 1;    /* multipath mode */
-    __u32 tf      : 1;    /* timing facility */
-    __u32 dnv     : 1;    /* device number valid */
-    __u32 dev     : 16;   /* device number */
-    __u8  lpm;            /* logical path mask */
-    __u8  pnom;           /* path not operational mask */
-    __u8  lpum;           /* last path used mask */
-    __u8  pim;            /* path installed mask */
-    __u16 mbi;            /* measurement-block index */
-    __u8  pom;            /* path operational mask */
-    __u8  pam;            /* path available mask */
-    __u8  chpid[8];       /* CHPID 0-7 (if available) */
-    __u32 unused1 : 8;    /* reserved zeros */
-    __u32 st      : 3;    /* subchannel type */
-    __u32 unused2 : 18;   /* reserved zeros */
-    __u32 mbfc    : 1;    /* measurement block format control */
-    __u32 xmwme   : 1;    /* extended measurement word mode enable */
-    __u32 csense  : 1;    /* concurrent sense; can be enabled ...*/
-                /*  ... per MSCH, however, if facility */
-                /*  ... is not installed, this results */
-                /*  ... in an operand exception.       */
+    __u32 intparm;      /* interruption parameter */
+    __u32 qf:1;         /* qdio facility */
+    __u32 w:1;
+    __u32 isc:3;        /* interruption sublass */
+    __u32 res5:3;       /* reserved zeros */
+    __u32 ena:1;        /* enabled */
+    __u32 lm:2;         /* limit mode */
+    __u32 mme:2;        /* measurement-mode enable */
+    __u32 mp:1;         /* multipath mode */
+    __u32 tf:1;         /* timing facility */
+    __u32 dnv:1;        /* device number valid */
+    __u32 dev:16;       /* device number */
+    __u8  lpm;          /* logical path mask */
+    __u8  pnom;         /* path not operational mask */
+    __u8  lpum;         /* last path used mask */
+    __u8  pim;          /* path installed mask */
+    __u16 mbi;          /* measurement-block index */
+    __u8  pom;          /* path operational mask */
+    __u8  pam;          /* path available mask */
+    __u8  chpid[8];     /* CHPID 0-7 (if available) */
+    __u32 unused1:8;    /* reserved zeros */
+    __u32 st:3;         /* subchannel type */
+    __u32 unused2:18;   /* reserved zeros */
+    __u32 mbfc:1;       /* measurement block format control */
+    __u32 xmwme:1;      /* extended measurement word mode enable */
+    __u32 csense:1;     /* concurrent sense; can be enabled ...*/
+                        /*  ... per MSCH, however, if facility */
+                        /*  ... is not installed, this results */
+                        /*  ... in an operand exception.       */
 } __attribute__ ((packed));
 
 /* Target SCHIB configuration. */
@@ -70,35 +70,72 @@ struct scsw {
     __u16 count;
 } __attribute__ ((packed));
 
-#define SCSW_FCTL_CLEAR_FUNC 0x1000
-#define SCSW_FCTL_HALT_FUNC 0x2000
+/* Function Control */
 #define SCSW_FCTL_START_FUNC 0x4000
+#define SCSW_FCTL_HALT_FUNC 0x2000
+#define SCSW_FCTL_CLEAR_FUNC 0x1000
+
+/* Activity Control */
+#define SCSW_ACTL_RESUME_PEND   0x0800
+#define SCSW_ACTL_START_PEND    0x0400
+#define SCSW_ACTL_HALT_PEND     0x0200
+#define SCSW_ACTL_CLEAR_PEND    0x0100
+#define SCSW_ACTL_CH_ACTIVE     0x0080
+#define SCSW_ACTL_DEV_ACTIVE    0x0040
+#define SCSW_ACTL_SUSPENDED     0x0020
+
+/* Status Control */
+#define SCSW_SCTL_ALERT         0x0010
+#define SCSW_SCTL_INTERMED      0x0008
+#define SCSW_SCTL_PRIMARY       0x0004
+#define SCSW_SCTL_SECONDARY     0x0002
+#define SCSW_SCTL_STATUS_PEND   0x0001
+
+/* SCSW Device Status Flags */
+#define SCSW_DSTAT_ATTN     0x80
+#define SCSW_DSTAT_STATMOD  0x40
+#define SCSW_DSTAT_CUEND    0x20
+#define SCSW_DSTAT_BUSY     0x10
+#define SCSW_DSTAT_CHEND    0x08
+#define SCSW_DSTAT_DEVEND   0x04
+#define SCSW_DSTAT_UCHK     0x02
+#define SCSW_DSTAT_UEXCP    0x01
+
+/* SCSW Subchannel Status Flags */
+#define SCSW_CSTAT_PCINT    0x80
+#define SCSW_CSTAT_BADLEN   0x40
+#define SCSW_CSTAT_PROGCHK  0x20
+#define SCSW_CSTAT_PROTCHK  0x10
+#define SCSW_CSTAT_CHDCHK   0x08
+#define SCSW_CSTAT_CHCCHK   0x04
+#define SCSW_CSTAT_ICCHK    0x02
+#define SCSW_CSTAT_CHAINCHK 0x01
 
 /*
  * subchannel information block
  */
-struct schib {
+typedef struct schib {
     struct pmcw pmcw;     /* path management control word */
     struct scsw scsw;     /* subchannel status word */
     __u64 mba;            /* measurement block address */
     __u8 mda[4];          /* model dependent area */
-} __attribute__ ((packed,aligned(4)));
-
-struct subchannel_id {
-        __u32 cssid  : 8;
-        __u32        : 4;
-        __u32 m      : 1;
-        __u32 ssid   : 2;
-        __u32 one    : 1;
-        __u32 sch_no : 16;
-} __attribute__ ((packed, aligned(4)));
+} __attribute__ ((packed, aligned(4))) Schib;
+
+typedef struct subchannel_id {
+        __u32 cssid:8;
+        __u32:4;
+        __u32 m:1;
+        __u32 ssid:2;
+        __u32 one:1;
+        __u32 sch_no:16;
+} __attribute__ ((packed, aligned(4))) SubChannelId;
 
 struct chsc_header {
     __u16 length;
     __u16 code;
 } __attribute__((packed));
 
-struct chsc_area_sda {
+typedef struct chsc_area_sda {
     struct chsc_header request;
     __u8 reserved1:4;
     __u8 format:4;
@@ -111,29 +148,49 @@ struct chsc_area_sda {
     __u32 reserved5:4;
     __u32 format2:4;
     __u32 reserved6:24;
-} __attribute__((packed));
+} __attribute__((packed)) ChscAreaSda;
 
 /*
  * TPI info structure
  */
 struct tpi_info {
     struct subchannel_id schid;
-    __u32 intparm;         /* interruption parameter */
-    __u32 adapter_IO : 1;
-    __u32 reserved2  : 1;
-    __u32 isc        : 3;
-    __u32 reserved3  : 12;
-    __u32 int_type   : 3;
-    __u32 reserved4  : 12;
+    __u32 intparm;      /* interruption parameter */
+    __u32 adapter_IO:1;
+    __u32 reserved2:1;
+    __u32 isc:3;
+    __u32 reserved3:12;
+    __u32 int_type:3;
+    __u32 reserved4:12;
 } __attribute__ ((packed, aligned(4)));
 
-/* channel command word (type 1) */
-struct ccw1 {
+/* channel command word (format 0) */
+typedef struct ccw0 {
+    __u8 cmd_code;
+    __u32 cda:24;
+    __u32 chainData:1;
+    __u32 chain:1;
+    __u32 sli:1;
+    __u32 skip:1;
+    __u32 pci:1;
+    __u32 ida:1;
+    __u32 suspend:1;
+    __u32 mida:1;
+    __u8 reserved;
+    __u16 count;
+} __attribute__ ((packed, aligned(8))) Ccw0;
+
+/* channel command word (format 1) */
+typedef struct ccw1 {
     __u8 cmd_code;
     __u8 flags;
     __u16 count;
     __u32 cda;
-} __attribute__ ((packed, aligned(8)));
+} __attribute__ ((packed, aligned(8))) Ccw1;
+
+/* do_cio() CCW formats */
+#define CCW_FMT0                 0x00
+#define CCW_FMT1                 0x01
 
 #define CCW_FLAG_DC              0x80
 #define CCW_FLAG_CC              0x40
@@ -143,11 +200,14 @@ struct ccw1 {
 #define CCW_FLAG_IDA             0x04
 #define CCW_FLAG_SUSPEND         0x02
 
+/* Common CCW commands */
+#define CCW_CMD_READ_IPL         0x02
 #define CCW_CMD_NOOP             0x03
 #define CCW_CMD_BASIC_SENSE      0x04
 #define CCW_CMD_TIC              0x08
 #define CCW_CMD_SENSE_ID         0xe4
 
+/* Virtio CCW commands */
 #define CCW_CMD_SET_VQ           0x13
 #define CCW_CMD_VDEV_RESET       0x33
 #define CCW_CMD_READ_FEAT        0x12
@@ -159,10 +219,16 @@ struct ccw1 {
 #define CCW_CMD_SET_CONF_IND     0x53
 #define CCW_CMD_READ_VQ_CONF     0x32
 
+/* DASD CCW commands */
+#define CCW_CMD_DASD_READ             0x06
+#define CCW_CMD_DASD_SEEK             0x07
+#define CCW_CMD_DASD_SEARCH_ID_EQ     0x31
+#define CCW_CMD_DASD_READ_MT          0x86
+
 /*
  * Command-mode operation request block
  */
-struct cmd_orb {
+typedef struct cmd_orb {
     __u32 intparm;    /* interruption parameter */
     __u32 key:4;      /* flags, like key, suspend control, etc. */
     __u32 spnd:1;     /* suspend control */
@@ -182,7 +248,7 @@ struct cmd_orb {
     __u32 zero:6;     /* reserved zeros */
     __u32 orbx:1;     /* ORB extension control */
     __u32 cpa;    /* channel program address */
-}  __attribute__ ((packed, aligned(4)));
+}  __attribute__ ((packed, aligned(4))) CmdOrb;
 
 struct ciw {
     __u8 type;
@@ -190,10 +256,15 @@ struct ciw {
     __u16 count;
 };
 
+#define CU_TYPE_UNKNOWN         0x0000
+#define CU_TYPE_DASD_2107       0x2107
+#define CU_TYPE_VIRTIO          0x3832
+#define CU_TYPE_DASD_3990       0x3990
+
 /*
  * sense-id response buffer layout
  */
-struct senseid {
+typedef struct senseid {
     /* common part */
     __u8  reserved;   /* always 0x'FF' */
     __u16 cu_type;    /* control unit type */
@@ -203,15 +274,94 @@ struct senseid {
     __u8  unused;     /* padding byte */
     /* extended part */
     struct ciw ciw[62];
-}  __attribute__ ((packed, aligned(4)));
+}  __attribute__ ((packed, aligned(4))) SenseId;
+
+/*
+ * architected values for first sense byte - common_status. Bits 0-5 of this
+ * field are common to all device types.
+ */
+#define SNS_STAT0_CMD_REJECT         0x80
+#define SNS_STAT0_INTERVENTION_REQ   0x40
+#define SNS_STAT0_BUS_OUT_CHECK      0x20
+#define SNS_STAT0_EQUIPMENT_CHECK    0x10
+#define SNS_STAT0_DATA_CHECK         0x08
+#define SNS_STAT0_OVERRUN            0x04
+#define SNS_STAT0_INCOMPL_DOMAIN     0x01
+
+/* ECKD DASD status[0] byte */
+#define SNS_STAT1_PERM_ERR           0x80
+#define SNS_STAT1_INV_TRACK_FORMAT   0x40
+#define SNS_STAT1_EOC                0x20
+#define SNS_STAT1_MESSAGE_TO_OPER    0x10
+#define SNS_STAT1_NO_REC_FOUND       0x08
+#define SNS_STAT1_FILE_PROTECTED     0x04
+#define SNS_STAT1_WRITE_INHIBITED    0x02
+#define SNS_STAT1_IMPRECISE_END      0x01
+
+/* ECKD DASD status[1] byte */
+#define SNS_STAT2_REQ_INH_WRITE      0x80
+#define SNS_STAT2_CORRECTABLE        0x40
+#define SNS_STAT2_FIRST_LOG_ERR      0x20
+#define SNS_STAT2_ENV_DATA_PRESENT   0x10
+#define SNS_STAT2_IMPRECISE_END      0x04
+
+/* ECKD DASD 24-byte Sense fmt_msg codes */
+#define SENSE24_FMT_PROG_SYS    0x0
+#define SENSE24_FMT_EQUIPMENT   0x2
+#define SENSE24_FMT_CONTROLLER  0x3
+#define SENSE24_FMT_MISC        0xF
+
+/* basic sense response buffer layout */
+typedef struct SenseDataEckdDasd {
+    uint8_t common_status;
+    uint8_t status[2];
+    uint8_t res_count;
+    uint8_t phys_drive_id;
+    uint8_t low_cyl_addr;
+    uint8_t head_high_cyl_addr;
+    uint8_t fmt_msg;
+    uint64_t fmt_dependent_info[2];
+    uint8_t reserved;
+    uint8_t program_action_code;
+    uint16_t config_info;
+    uint8_t mcode_hicyl;
+    uint8_t cyl_head_addr[3];
+}  __attribute__ ((packed, aligned(4))) SenseDataEckdDasd;
+
+#define ECKD_SENSE24_GET_FMT(sd)     (sd->fmt_msg & 0xF0 >> 4)
+#define ECKD_SENSE24_GET_MSG(sd)     (sd->fmt_msg & 0x0F)
+
+#define unit_check(irb)         ((irb)->scsw.dstat & SCSW_DSTAT_UCHK)
+#define iface_ctrl_check(irb)   ((irb)->scsw.cstat & SCSW_CSTAT_ICCHK)
 
 /* interruption response block */
-struct irb {
+typedef struct irb {
     struct scsw scsw;
     __u32 esw[5];
     __u32 ecw[8];
     __u32 emw[8];
-}  __attribute__ ((packed, aligned(4)));
+}  __attribute__ ((packed, aligned(4))) Irb;
+
+/* Used for SEEK ccw commands */
+typedef struct CcwSeekData {
+    uint16_t reserved;
+    uint16_t cyl;
+    uint16_t head;
+} __attribute__((packed)) CcwSeekData;
+
+/* Used for SEARCH ID ccw commands */
+typedef struct CcwSearchIdData {
+    uint16_t cyl;
+    uint16_t head;
+    uint8_t record;
+} __attribute__((packed)) CcwSearchIdData;
+
+int enable_mss_facility(void);
+void enable_subchannel(SubChannelId schid);
+uint16_t cu_type(SubChannelId schid);
+int basic_sense(SubChannelId schid, uint16_t cutype, void *sense_data,
+                 uint16_t data_size);
+int do_cio(SubChannelId schid, uint16_t cutype, uint32_t ccw_addr, int fmt);
 
 /*
  * Some S390 specific IO instructions as inline
diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c
new file mode 100644
index 0000000..0fc879b
--- /dev/null
+++ b/pc-bios/s390-ccw/dasd-ipl.c
@@ -0,0 +1,235 @@
+/*
+ * S390 IPL (boot) from a real DASD device via vfio framework.
+ *
+ * Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * 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.
+ */
+
+#include "libc.h"
+#include "s390-ccw.h"
+#include "s390-arch.h"
+#include "dasd-ipl.h"
+#include "helper.h"
+
+static char prefix_page[PAGE_SIZE * 2]
+            __attribute__((__aligned__(PAGE_SIZE * 2)));
+
+static void enable_prefixing(void)
+{
+    memcpy(&prefix_page, lowcore, 4096);
+    set_prefix(ptr2u32(&prefix_page));
+}
+
+static void disable_prefixing(void)
+{
+    set_prefix(0);
+    /* Copy io interrupt info back to low core */
+    memcpy((void *)&lowcore->subchannel_id, prefix_page + 0xB8, 12);
+}
+
+static bool is_read_tic_ccw_chain(Ccw0 *ccw)
+{
+    Ccw0 *next_ccw = ccw + 1;
+
+    return ((ccw->cmd_code == CCW_CMD_DASD_READ ||
+            ccw->cmd_code == CCW_CMD_DASD_READ_MT) &&
+            ccw->chain && next_ccw->cmd_code == CCW_CMD_TIC);
+}
+
+static bool dynamic_cp_fixup(uint32_t ccw_addr, uint32_t  *next_cpa)
+{
+    Ccw0 *cur_ccw = (Ccw0 *)(uint64_t)ccw_addr;
+    Ccw0 *tic_ccw;
+
+    while (true) {
+        /* Skip over inline TIC (it might not have the chain bit on)  */
+        if (cur_ccw->cmd_code == CCW_CMD_TIC &&
+            cur_ccw->cda == ptr2u32(cur_ccw) - 8) {
+            cur_ccw += 1;
+            continue;
+        }
+
+        if (!cur_ccw->chain) {
+            break;
+        }
+        if (is_read_tic_ccw_chain(cur_ccw)) {
+            /*
+             * Breaking a chain of CCWs may alter the semantics or even the
+             * validity of a channel program. The heuristic implemented below
+             * seems to work well in practice for the channel programs
+             * generated by zipl.
+             */
+            tic_ccw = cur_ccw + 1;
+            *next_cpa = tic_ccw->cda;
+            cur_ccw->chain = 0;
+            return true;
+        }
+        cur_ccw += 1;
+    }
+    return false;
+}
+
+static int run_dynamic_ccw_program(SubChannelId schid, uint16_t cutype,
+                                   uint32_t cpa)
+{
+    bool has_next;
+    uint32_t next_cpa = 0;
+    int rc;
+
+    do {
+        has_next = dynamic_cp_fixup(cpa, &next_cpa);
+
+        print_int("executing ccw chain at ", cpa);
+        enable_prefixing();
+        rc = do_cio(schid, cutype, cpa, CCW_FMT0);
+        disable_prefixing();
+
+        if (rc) {
+            break;
+        }
+        cpa = next_cpa;
+    } while (has_next);
+
+    return rc;
+}
+
+static void make_readipl(void)
+{
+    Ccw0 *ccwIplRead = (Ccw0 *)0x00;
+
+    /* Create Read IPL ccw at address 0 */
+    ccwIplRead->cmd_code = CCW_CMD_READ_IPL;
+    ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */
+    ccwIplRead->chain = 0; /* Chain flag */
+    ccwIplRead->count = 0x18; /* Read 0x18 bytes of data */
+}
+
+static void run_readipl(SubChannelId schid, uint16_t cutype)
+{
+    if (do_cio(schid, cutype, 0x00, CCW_FMT0)) {
+        panic("dasd-ipl: Failed to run Read IPL channel program\n");
+    }
+}
+
+/*
+ * The architecture states that IPL1 data should consist of a psw followed by
+ * format-0 READ and TIC CCWs. Let's sanity check.
+ */
+static void check_ipl1(void)
+{
+    Ccw0 *ccwread = (Ccw0 *)0x08;
+    Ccw0 *ccwtic = (Ccw0 *)0x10;
+
+    if (ccwread->cmd_code != CCW_CMD_DASD_READ ||
+        ccwtic->cmd_code != CCW_CMD_TIC) {
+        panic("dasd-ipl: IPL1 data invalid. Is this disk really bootable?\n");
+    }
+}
+
+static void check_ipl2(uint32_t ipl2_addr)
+{
+    Ccw0 *ccw = u32toptr(ipl2_addr);
+
+    if (ipl2_addr == 0x00) {
+        panic("IPL2 address invalid. Is this disk really bootable?\n");
+    }
+    if (ccw->cmd_code == 0x00) {
+        panic("IPL2 ccw data invalid. Is this disk really bootable?\n");
+    }
+}
+
+static uint32_t read_ipl2_addr(void)
+{
+    Ccw0 *ccwtic = (Ccw0 *)0x10;
+
+    return ccwtic->cda;
+}
+
+static void ipl1_fixup(void)
+{
+    Ccw0 *ccwSeek = (Ccw0 *) 0x08;
+    Ccw0 *ccwSearchID = (Ccw0 *) 0x10;
+    Ccw0 *ccwSearchTic = (Ccw0 *) 0x18;
+    Ccw0 *ccwRead = (Ccw0 *) 0x20;
+    CcwSeekData *seekData = (CcwSeekData *) 0x30;
+    CcwSearchIdData *searchData = (CcwSearchIdData *) 0x38;
+
+    /* move IPL1 CCWs to make room for CCWs needed to locate record 2 */
+    memcpy(ccwRead, (void *)0x08, 16);
+
+    /* Disable chaining so we don't TIC to IPL2 channel program */
+    ccwRead->chain = 0x00;
+
+    ccwSeek->cmd_code = CCW_CMD_DASD_SEEK;
+    ccwSeek->cda = ptr2u32(seekData);
+    ccwSeek->chain = 1;
+    ccwSeek->count = sizeof(*seekData);
+    seekData->reserved = 0x00;
+    seekData->cyl = 0x00;
+    seekData->head = 0x00;
+
+    ccwSearchID->cmd_code = CCW_CMD_DASD_SEARCH_ID_EQ;
+    ccwSearchID->cda = ptr2u32(searchData);
+    ccwSearchID->chain = 1;
+    ccwSearchID->count = sizeof(*searchData);
+    searchData->cyl = 0;
+    searchData->head = 0;
+    searchData->record = 2;
+
+    /* Go back to Search CCW if correct record not yet found */
+    ccwSearchTic->cmd_code = CCW_CMD_TIC;
+    ccwSearchTic->cda = ptr2u32(ccwSearchID);
+}
+
+static void run_ipl1(SubChannelId schid, uint16_t cutype)
+ {
+    uint32_t startAddr = 0x08;
+
+    if (do_cio(schid, cutype, startAddr, CCW_FMT0)) {
+        panic("dasd-ipl: Failed to run IPL1 channel program\n");
+    }
+}
+
+static void run_ipl2(SubChannelId schid, uint16_t cutype, uint32_t addr)
+{
+    if (run_dynamic_ccw_program(schid, cutype, addr)) {
+        panic("dasd-ipl: Failed to run IPL2 channel program\n");
+    }
+}
+
+/*
+ * Limitations in vfio-ccw support complicate the IPL process. Details can
+ * be found in docs/devel/s390-dasd-ipl.txt
+ */
+void dasd_ipl(SubChannelId schid, uint16_t cutype)
+{
+    PSWLegacy *pswl = (PSWLegacy *) 0x00;
+    uint32_t ipl2_addr;
+
+    /* Construct Read IPL CCW and run it to read IPL1 from boot disk */
+    make_readipl();
+    run_readipl(schid, cutype);
+    ipl2_addr = read_ipl2_addr();
+    check_ipl1();
+
+    /*
+     * Fixup IPL1 channel program to account for vfio-ccw limitations, then run
+     * it to read IPL2 channel program from boot disk.
+     */
+    ipl1_fixup();
+    run_ipl1(schid, cutype);
+    check_ipl2(ipl2_addr);
+
+    /*
+     * Run IPL2 channel program to read operating system code from boot disk
+     */
+    run_ipl2(schid, cutype, ipl2_addr);
+
+    /* Transfer control to the guest operating system */
+    pswl->mask |= PSW_MASK_EAMODE;   /* Force z-mode */
+    pswl->addr |= PSW_MASK_BAMODE;   /* ...          */
+    jump_to_low_kernel();
+}
diff --git a/pc-bios/s390-ccw/dasd-ipl.h b/pc-bios/s390-ccw/dasd-ipl.h
new file mode 100644
index 0000000..c394828
--- /dev/null
+++ b/pc-bios/s390-ccw/dasd-ipl.h
@@ -0,0 +1,16 @@
+/*
+ * S390 IPL (boot) from a real DASD device via vfio framework.
+ *
+ * Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * 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.
+ */
+
+#ifndef DASD_IPL_H
+#define DASD_IPL_H
+
+void dasd_ipl(SubChannelId schid, uint16_t cutype);
+
+#endif /* DASD_IPL_H */
diff --git a/pc-bios/s390-ccw/helper.h b/pc-bios/s390-ccw/helper.h
new file mode 100644
index 0000000..78d5bc7
--- /dev/null
+++ b/pc-bios/s390-ccw/helper.h
@@ -0,0 +1,31 @@
+/*
+ * Helper Functions
+ *
+ * Copyright (c) 2019 IBM Corp.
+ *
+ * Author(s): Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * 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.
+ */
+
+#ifndef S390_CCW_HELPER_H
+#define S390_CCW_HELPER_H
+
+#include "s390-ccw.h"
+
+/* Avoids compiler warnings when casting a pointer to a u32 */
+static inline uint32_t ptr2u32(void *ptr)
+{
+    IPL_assert((uint64_t)ptr <= 0xffffffff, "ptr2u32: ptr too large");
+    return (uint32_t)(uint64_t)ptr;
+}
+
+/* Avoids compiler warnings when casting a u32 to a pointer */
+static inline void *u32toptr(uint32_t n)
+{
+    return (void *)(uint64_t)n;
+}
+
+#endif
diff --git a/pc-bios/s390-ccw/libc.h b/pc-bios/s390-ccw/libc.h
index 818517f..bcdc457 100644
--- a/pc-bios/s390-ccw/libc.h
+++ b/pc-bios/s390-ccw/libc.h
@@ -67,6 +67,17 @@ static inline size_t strlen(const char *str)
     return i;
 }
 
+static inline char *strcat(char *dest, const char *src)
+{
+    int i;
+    char *dest_end = dest + strlen(dest);
+
+    for (i = 0; i <= strlen(src); i++) {
+        dest_end[i] = src[i];
+    }
+    return dest;
+}
+
 static inline int isdigit(int c)
 {
     return (c >= '0') && (c <= '9');
diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
index 544851d..a69c733 100644
--- a/pc-bios/s390-ccw/main.c
+++ b/pc-bios/s390-ccw/main.c
@@ -9,21 +9,27 @@
  */
 
 #include "libc.h"
+#include "s390-arch.h"
 #include "s390-ccw.h"
+#include "cio.h"
 #include "virtio.h"
+#include "dasd-ipl.h"
 
 char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 static SubChannelId blk_schid = { .one = 1 };
-IplParameterBlock iplb __attribute__((__aligned__(PAGE_SIZE)));
 static char loadparm_str[LOADPARM_LEN + 1] = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
 QemuIplParameters qipl;
+IplParameterBlock iplb __attribute__((__aligned__(PAGE_SIZE)));
+static bool have_iplb;
+static uint16_t cutype;
+LowCore const *lowcore; /* Yes, this *is* a pointer to address 0 */
 
 #define LOADPARM_PROMPT "PROMPT  "
 #define LOADPARM_EMPTY  "        "
 #define BOOT_MENU_FLAG_MASK (QIPL_FLAG_BM_OPTS_CMD | QIPL_FLAG_BM_OPTS_ZIPL)
 
 /*
- * Priniciples of Operations (SA22-7832-09) chapter 17 requires that
+ * Principles of Operations (SA22-7832-09) chapter 17 requires that
  * a subsystem-identification is at 184-187 and bytes 188-191 are zero
  * after list-directed-IPL and ccw-IPL.
  */
@@ -48,29 +54,64 @@ unsigned int get_loadparm_index(void)
     return atoui(loadparm_str);
 }
 
-static bool find_dev(Schib *schib, int dev_no)
+/*
+ * Find the subchannel connected to the given device (dev_no) and fill in the
+ * subchannel information block (schib) with the connected subchannel's info.
+ * NOTE: The global variable blk_schid is updated to contain the subchannel
+ * information.
+ *
+ * If the caller gives dev_no=-1 then the user did not specify a boot device.
+ * In this case we'll just use the first potentially bootable device we find.
+ */
+static bool find_subch(int dev_no)
 {
+    Schib schib;
     int i, r;
+    bool is_virtio;
 
     for (i = 0; i < 0x10000; i++) {
         blk_schid.sch_no = i;
-        r = stsch_err(blk_schid, schib);
+        r = stsch_err(blk_schid, &schib);
         if ((r == 3) || (r == -EIO)) {
             break;
         }
-        if (!schib->pmcw.dnv) {
-            continue;
-        }
-        if (!virtio_is_supported(blk_schid)) {
+        if (!schib.pmcw.dnv) {
             continue;
         }
-        /* Skip net devices since no IPLB is created and therefore no
-         * no network bootloader has been loaded
+
+        enable_subchannel(blk_schid);
+        cutype = cu_type(blk_schid);
+
+        /*
+         * Note: we always have to run virtio_is_supported() here to make
+         * sure that the vdev.senseid data gets pre-initialized correctly
          */
-        if (virtio_get_device_type() == VIRTIO_ID_NET && dev_no < 0) {
-            continue;
+        is_virtio = virtio_is_supported(blk_schid);
+
+        /* No specific devno given, just return 1st possibly bootable device */
+        if (dev_no < 0) {
+            switch (cutype) {
+            case CU_TYPE_VIRTIO:
+                if (is_virtio) {
+                    /*
+                     * Skip net devices since no IPLB is created and therefore
+                     * no network bootloader has been loaded
+                     */
+                    if (virtio_get_device_type() != VIRTIO_ID_NET) {
+                        return true;
+                    }
+                }
+                continue;
+            case CU_TYPE_DASD_3990:
+            case CU_TYPE_DASD_2107:
+                return true;
+            default:
+                continue;
+            }
         }
-        if ((dev_no < 0) || (schib->pmcw.dev == dev_no)) {
+
+        /* Caller asked for a specific devno */
+        if (schib.pmcw.dev == dev_no) {
             return true;
         }
     }
@@ -99,68 +140,88 @@ static void menu_setup(void)
     }
 }
 
-static void virtio_setup(void)
+/*
+ * Initialize the channel I/O subsystem so we can talk to our ipl/boot device.
+ */
+static void css_setup(void)
 {
-    Schib schib;
-    int ssid;
-    bool found = false;
-    uint16_t dev_no;
-    char ldp[] = "LOADPARM=[________]\n";
-    VDev *vdev = virtio_get_device();
-    QemuIplParameters *early_qipl = (QemuIplParameters *)QIPL_ADDRESS;
-
     /*
-     * 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.
+     * Unconditionally enable mss support. In every sane configuration this
+     * will succeed; and even if it doesn't, stsch_err() can handle it.
      */
     enable_mss_facility();
+}
+
+/*
+ * Collect various pieces of information from the hypervisor/hardware that
+ * we'll use to determine exactly how we'll boot.
+ */
+static void boot_setup(void)
+{
+    char lpmsg[] = "LOADPARM=[________]\n";
 
     sclp_get_loadparm_ascii(loadparm_str);
-    memcpy(ldp + 10, loadparm_str, LOADPARM_LEN);
-    sclp_print(ldp);
+    memcpy(lpmsg + 10, loadparm_str, 8);
+    sclp_print(lpmsg);
 
-    memcpy(&qipl, early_qipl, sizeof(QemuIplParameters));
+    have_iplb = store_iplb(&iplb);
+}
 
-    if (store_iplb(&iplb)) {
-        switch (iplb.pbt) {
-        case S390_IPL_TYPE_CCW:
-            dev_no = iplb.ccw.devno;
-            debug_print_int("device no. ", dev_no);
-            blk_schid.ssid = iplb.ccw.ssid & 0x3;
-            debug_print_int("ssid ", blk_schid.ssid);
-            found = find_dev(&schib, dev_no);
-            break;
-        case S390_IPL_TYPE_QEMU_SCSI:
-            vdev->scsi_device_selected = true;
-            vdev->selected_scsi_device.channel = iplb.scsi.channel;
-            vdev->selected_scsi_device.target = iplb.scsi.target;
-            vdev->selected_scsi_device.lun = iplb.scsi.lun;
-            blk_schid.ssid = iplb.scsi.ssid & 0x3;
-            found = find_dev(&schib, iplb.scsi.devno);
-            break;
-        default:
-            panic("List-directed IPL not supported yet!\n");
-        }
-        menu_setup();
-    } else {
+static void find_boot_device(void)
+{
+    VDev *vdev = virtio_get_device();
+    int ssid;
+    bool found;
+
+    if (!have_iplb) {
         for (ssid = 0; ssid < 0x3; ssid++) {
             blk_schid.ssid = ssid;
-            found = find_dev(&schib, -1);
+            found = find_subch(-1);
             if (found) {
-                break;
+                return;
             }
         }
+        panic("Could not find a suitable boot device (none specified)\n");
+    }
+
+    switch (iplb.pbt) {
+    case S390_IPL_TYPE_CCW:
+        debug_print_int("device no. ", iplb.ccw.devno);
+        blk_schid.ssid = iplb.ccw.ssid & 0x3;
+        debug_print_int("ssid ", blk_schid.ssid);
+        found = find_subch(iplb.ccw.devno);
+        break;
+    case S390_IPL_TYPE_QEMU_SCSI:
+        vdev->scsi_device_selected = true;
+        vdev->selected_scsi_device.channel = iplb.scsi.channel;
+        vdev->selected_scsi_device.target = iplb.scsi.target;
+        vdev->selected_scsi_device.lun = iplb.scsi.lun;
+        blk_schid.ssid = iplb.scsi.ssid & 0x3;
+        found = find_subch(iplb.scsi.devno);
+        break;
+    default:
+        panic("List-directed IPL not supported yet!\n");
     }
 
-    IPL_assert(found, "No virtio device found");
+    IPL_assert(found, "Boot device not found\n");
+}
+
+static void virtio_setup(void)
+{
+    VDev *vdev = virtio_get_device();
+    QemuIplParameters *early_qipl = (QemuIplParameters *)QIPL_ADDRESS;
+
+    memcpy(&qipl, early_qipl, sizeof(QemuIplParameters));
+
+    if (have_iplb) {
+        menu_setup();
+    }
 
     if (virtio_get_device_type() == VIRTIO_ID_NET) {
         sclp_print("Network boot device detected\n");
         vdev->netboot_start_addr = qipl.netboot_start_addr;
     } else {
         virtio_blk_setup_device(blk_schid);
-
         IPL_assert(virtio_ipl_disk_is_valid(), "No valid IPL device detected");
     }
 }
@@ -168,9 +229,24 @@ static void virtio_setup(void)
 int main(void)
 {
     sclp_setup();
-    virtio_setup();
-
-    zipl_load(); /* no return */
+    css_setup();
+    boot_setup();
+    find_boot_device();
+    enable_subchannel(blk_schid);
+
+    switch (cutype) {
+    case CU_TYPE_DASD_3990:
+    case CU_TYPE_DASD_2107:
+        dasd_ipl(blk_schid, cutype); /* no return */
+        break;
+    case CU_TYPE_VIRTIO:
+        virtio_setup();
+        zipl_load(); /* no return */
+        break;
+    default:
+        print_int("Attempting to boot from unexpected device type", cutype);
+        panic("");
+    }
 
     panic("Failed to load OS from hard disk\n");
     return 0; /* make compiler happy */
diff --git a/pc-bios/s390-ccw/netboot.mak b/pc-bios/s390-ccw/netboot.mak
index 14e96b2..5eefb7c 100644
--- a/pc-bios/s390-ccw/netboot.mak
+++ b/pc-bios/s390-ccw/netboot.mak
@@ -1,7 +1,7 @@
 
 SLOF_DIR := $(SRC_PATH)/roms/SLOF
 
-NETOBJS := start.o sclp.o virtio.o virtio-net.o jump2ipl.o netmain.o \
+NETOBJS := start.o sclp.o cio.o virtio.o virtio-net.o jump2ipl.o netmain.o \
 	   libnet.a libc.a
 
 LIBC_INC := -nostdinc -I$(SLOF_DIR)/lib/libc/include
diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
index 0392131..f3542cb 100644
--- a/pc-bios/s390-ccw/netmain.c
+++ b/pc-bios/s390-ccw/netmain.c
@@ -33,6 +33,7 @@
 #include <pxelinux.h>
 
 #include "s390-ccw.h"
+#include "cio.h"
 #include "virtio.h"
 
 #define DEFAULT_BOOT_RETRIES 10
@@ -475,6 +476,7 @@ static bool find_net_dev(Schib *schib, int dev_no)
         if (!schib->pmcw.dnv) {
             continue;
         }
+        enable_subchannel(net_schid);
         if (!virtio_is_supported(net_schid)) {
             continue;
         }
diff --git a/pc-bios/s390-ccw/s390-arch.h b/pc-bios/s390-ccw/s390-arch.h
new file mode 100644
index 0000000..504fc7c
--- /dev/null
+++ b/pc-bios/s390-ccw/s390-arch.h
@@ -0,0 +1,103 @@
+/*
+ * S390 Basic Architecture
+ *
+ * Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
+ *
+ * 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.
+ */
+
+#ifndef S390_ARCH_H
+#define S390_ARCH_H
+
+typedef struct PSW {
+    uint64_t mask;
+    uint64_t addr;
+} __attribute__ ((aligned(8))) PSW;
+_Static_assert(sizeof(struct PSW) == 16, "PSW size incorrect");
+
+/* Older PSW format used by LPSW instruction */
+typedef struct PSWLegacy {
+    uint32_t mask;
+    uint32_t addr;
+} __attribute__ ((aligned(8))) PSWLegacy;
+_Static_assert(sizeof(struct PSWLegacy) == 8, "PSWLegacy size incorrect");
+
+/* s390 psw bit masks */
+#define PSW_MASK_IOINT      0x0200000000000000ULL
+#define PSW_MASK_WAIT       0x0002000000000000ULL
+#define PSW_MASK_EAMODE     0x0000000100000000ULL
+#define PSW_MASK_BAMODE     0x0000000080000000ULL
+#define PSW_MASK_ZMODE      (PSW_MASK_EAMODE | PSW_MASK_BAMODE)
+
+/* Low core mapping */
+typedef struct LowCore {
+    /* prefix area: defined by architecture */
+    PSWLegacy       ipl_psw;                  /* 0x000 */
+    uint32_t        ccw1[2];                  /* 0x008 */
+    uint32_t        ccw2[2];                  /* 0x010 */
+    uint8_t         pad1[0x80 - 0x18];        /* 0x018 */
+    uint32_t        ext_params;               /* 0x080 */
+    uint16_t        cpu_addr;                 /* 0x084 */
+    uint16_t        ext_int_code;             /* 0x086 */
+    uint16_t        svc_ilen;                 /* 0x088 */
+    uint16_t        svc_code;                 /* 0x08a */
+    uint16_t        pgm_ilen;                 /* 0x08c */
+    uint16_t        pgm_code;                 /* 0x08e */
+    uint32_t        data_exc_code;            /* 0x090 */
+    uint16_t        mon_class_num;            /* 0x094 */
+    uint16_t        per_perc_atmid;           /* 0x096 */
+    uint64_t        per_address;              /* 0x098 */
+    uint8_t         exc_access_id;            /* 0x0a0 */
+    uint8_t         per_access_id;            /* 0x0a1 */
+    uint8_t         op_access_id;             /* 0x0a2 */
+    uint8_t         ar_access_id;             /* 0x0a3 */
+    uint8_t         pad2[0xA8 - 0xA4];        /* 0x0a4 */
+    uint64_t        trans_exc_code;           /* 0x0a8 */
+    uint64_t        monitor_code;             /* 0x0b0 */
+    uint16_t        subchannel_id;            /* 0x0b8 */
+    uint16_t        subchannel_nr;            /* 0x0ba */
+    uint32_t        io_int_parm;              /* 0x0bc */
+    uint32_t        io_int_word;              /* 0x0c0 */
+    uint8_t         pad3[0xc8 - 0xc4];        /* 0x0c4 */
+    uint32_t        stfl_fac_list;            /* 0x0c8 */
+    uint8_t         pad4[0xe8 - 0xcc];        /* 0x0cc */
+    uint64_t        mcic;                     /* 0x0e8 */
+    uint8_t         pad5[0xf4 - 0xf0];        /* 0x0f0 */
+    uint32_t        external_damage_code;     /* 0x0f4 */
+    uint64_t        failing_storage_address;  /* 0x0f8 */
+    uint8_t         pad6[0x110 - 0x100];      /* 0x100 */
+    uint64_t        per_breaking_event_addr;  /* 0x110 */
+    uint8_t         pad7[0x120 - 0x118];      /* 0x118 */
+    PSW             restart_old_psw;          /* 0x120 */
+    PSW             external_old_psw;         /* 0x130 */
+    PSW             svc_old_psw;              /* 0x140 */
+    PSW             program_old_psw;          /* 0x150 */
+    PSW             mcck_old_psw;             /* 0x160 */
+    PSW             io_old_psw;               /* 0x170 */
+    uint8_t         pad8[0x1a0 - 0x180];      /* 0x180 */
+    PSW             restart_new_psw;          /* 0x1a0 */
+    PSW             external_new_psw;         /* 0x1b0 */
+    PSW             svc_new_psw;              /* 0x1c0 */
+    PSW             program_new_psw;          /* 0x1d0 */
+    PSW             mcck_new_psw;             /* 0x1e0 */
+    PSW             io_new_psw;               /* 0x1f0 */
+} __attribute__((packed, aligned(8192))) LowCore;
+
+extern LowCore const *lowcore;
+
+static inline void set_prefix(uint32_t address)
+{
+    asm volatile("spx %0" : : "m" (address) : "memory");
+}
+
+static inline uint32_t store_prefix(void)
+{
+    uint32_t address;
+
+    asm volatile("stpx %0" : "=m" (address));
+    return address;
+}
+
+#endif
diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
index 9828aa2..11bce7d 100644
--- a/pc-bios/s390-ccw/s390-ccw.h
+++ b/pc-bios/s390-ccw/s390-ccw.h
@@ -49,17 +49,10 @@ typedef unsigned long long __u64;
 #include "cio.h"
 #include "iplb.h"
 
-typedef struct irb Irb;
-typedef struct ccw1 Ccw1;
-typedef struct cmd_orb CmdOrb;
-typedef struct schib Schib;
-typedef struct chsc_area_sda ChscAreaSda;
-typedef struct senseid SenseId;
-typedef struct subchannel_id SubChannelId;
-
 /* start.s */
 void disabled_wait(void);
 void consume_sclp_int(void);
+void consume_io_int(void);
 
 /* main.c */
 void panic(const char *string);
@@ -80,7 +73,6 @@ unsigned long virtio_load_direct(ulong rec_list1, ulong rec_list2,
 bool virtio_is_supported(SubChannelId schid);
 void virtio_blk_setup_device(SubChannelId schid);
 int virtio_read(ulong sector, void *load_addr);
-int enable_mss_facility(void);
 u64 get_clock(void);
 ulong get_second(void);
 
diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
index 5c22cb0..aa8fceb 100644
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -71,6 +71,26 @@ consume_sclp_int:
         larl %r1, enabled_wait_psw
         lpswe 0(%r1)
 
+/*
+ * void consume_io_int(void)
+ *
+ * eats one I/O interrupt
+ */
+        .globl consume_io_int
+consume_io_int:
+        /* enable I/O interrupts in cr6 */
+        stctg %c6,%c6,0(%r15)
+        oi    4(%r15), 0xff
+        lctlg %c6,%c6,0(%r15)
+        /* prepare i/o call handler */
+        larl  %r1, io_new_code
+        stg   %r1, 0x1f8
+        larl  %r1, io_new_mask
+        mvc   0x1f0(8),0(%r1)
+        /* load enabled wait PSW */
+        larl  %r1, enabled_wait_psw
+        lpswe 0(%r1)
+
 external_new_code:
         /* disable service interrupts in cr0 */
         stctg   %c0,%c0,0(%r15)
@@ -78,6 +98,13 @@ external_new_code:
         lctlg   %c0,%c0,0(%r15)
         br      %r14
 
+io_new_code:
+        /* disable I/O interrupts in cr6 */
+        stctg %c6,%c6,0(%r15)
+        ni    4(%r15), 0x00
+        lctlg %c6,%c6,0(%r15)
+        br    %r14
+
         .align  8
 disabled_wait_psw:
         .quad   0x0002000180000000,0x0000000000000000
@@ -85,3 +112,5 @@ enabled_wait_psw:
         .quad   0x0302000180000000,0x0000000000000000
 external_new_mask:
         .quad   0x0000000180000000
+io_new_mask:
+        .quad   0x0000000180000000
diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index cdb66f4..fb40ca9 100644
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -10,9 +10,11 @@
 
 #include "libc.h"
 #include "s390-ccw.h"
+#include "cio.h"
 #include "virtio.h"
 #include "virtio-scsi.h"
 #include "bswap.h"
+#include "helper.h"
 
 #define VRING_WAIT_REPLY_TIMEOUT 30
 
@@ -20,8 +22,6 @@ static VRing block[VIRTIO_MAX_VQS];
 static char ring_area[VIRTIO_RING_SIZE * VIRTIO_MAX_VQS]
                      __attribute__((__aligned__(PAGE_SIZE)));
 
-static char chsc_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
-
 static VDev vdev = {
     .nr_vqs = 1,
     .vrings = block,
@@ -90,38 +90,19 @@ int drain_irqs(SubChannelId schid)
     }
 }
 
-static int run_ccw(VDev *vdev, int cmd, void *ptr, int len)
+static int run_ccw(VDev *vdev, int cmd, void *ptr, int len, bool sli)
 {
     Ccw1 ccw = {};
-    CmdOrb orb = {};
-    Schib schib;
-    int r;
-
-    /* start command processing */
-    stsch_err(vdev->schid, &schib);
-    /* enable the subchannel for IPL device */
-    schib.pmcw.ena = 1;
-    msch(vdev->schid, &schib);
-
-    /* start subchannel command */
-    orb.fmt = 1;
-    orb.cpa = (u32)(long)&ccw;
-    orb.lpm = 0x80;
 
     ccw.cmd_code = cmd;
     ccw.cda = (long)ptr;
     ccw.count = len;
 
-    r = ssch(vdev->schid, &orb);
-    /*
-     * XXX Wait until device is done processing the CCW. For now we can
-     *     assume that a simple tsch will have finished the CCW processing,
-     *     but the architecture allows for asynchronous operation
-     */
-    if (!r) {
-        r = drain_irqs(vdev->schid);
+    if (sli) {
+        ccw.flags |= CCW_FLAG_SLI;
     }
-    return r;
+
+    return do_cio(vdev->schid, vdev->senseid.cu_type, ptr2u32(&ccw), CCW_FMT1);
 }
 
 static void vring_init(VRing *vr, VqInfo *info)
@@ -263,7 +244,7 @@ void virtio_setup_ccw(VDev *vdev)
     vdev->config.blk.blk_size = 0; /* mark "illegal" - setup started... */
     vdev->guessed_disk_nature = VIRTIO_GDN_NONE;
 
-    run_ccw(vdev, CCW_CMD_VDEV_RESET, NULL, 0);
+    run_ccw(vdev, CCW_CMD_VDEV_RESET, NULL, 0, false);
 
     switch (vdev->senseid.cu_model) {
     case VIRTIO_ID_NET:
@@ -284,18 +265,19 @@ void virtio_setup_ccw(VDev *vdev)
     default:
         panic("Unsupported virtio device\n");
     }
-    IPL_assert(run_ccw(vdev, CCW_CMD_READ_CONF, &vdev->config, cfg_size) == 0,
-               "Could not get block device configuration");
+    IPL_assert(
+        run_ccw(vdev, CCW_CMD_READ_CONF, &vdev->config, cfg_size, false) == 0,
+       "Could not get block device configuration");
 
     /* Feature negotiation */
     for (i = 0; i < ARRAY_SIZE(vdev->guest_features); i++) {
         feats.features = 0;
         feats.index = i;
-        rc = run_ccw(vdev, CCW_CMD_READ_FEAT, &feats, sizeof(feats));
+        rc = run_ccw(vdev, CCW_CMD_READ_FEAT, &feats, sizeof(feats), false);
         IPL_assert(rc == 0, "Could not get features bits");
         vdev->guest_features[i] &= bswap32(feats.features);
         feats.features = bswap32(vdev->guest_features[i]);
-        rc = run_ccw(vdev, CCW_CMD_WRITE_FEAT, &feats, sizeof(feats));
+        rc = run_ccw(vdev, CCW_CMD_WRITE_FEAT, &feats, sizeof(feats), false);
         IPL_assert(rc == 0, "Could not set features bits");
     }
 
@@ -312,16 +294,17 @@ void virtio_setup_ccw(VDev *vdev)
         };
 
         IPL_assert(
-            run_ccw(vdev, CCW_CMD_READ_VQ_CONF, &config, sizeof(config)) == 0,
+            run_ccw(vdev, CCW_CMD_READ_VQ_CONF, &config, sizeof(config), false) == 0,
             "Could not get block device VQ configuration");
         info.num = config.num;
         vring_init(&vdev->vrings[i], &info);
         vdev->vrings[i].schid = vdev->schid;
-        IPL_assert(run_ccw(vdev, CCW_CMD_SET_VQ, &info, sizeof(info)) == 0,
-                   "Cannot set VQ info");
+        IPL_assert(
+            run_ccw(vdev, CCW_CMD_SET_VQ, &info, sizeof(info), false) == 0,
+            "Cannot set VQ info");
     }
     IPL_assert(
-        run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status, sizeof(status)) == 0,
+        run_ccw(vdev, CCW_CMD_WRITE_STATUS, &status, sizeof(status), false) == 0,
         "Could not write status to host");
 }
 
@@ -329,8 +312,15 @@ bool virtio_is_supported(SubChannelId schid)
 {
     vdev.schid = schid;
     memset(&vdev.senseid, 0, sizeof(vdev.senseid));
-    /* run sense id command */
-    if (run_ccw(&vdev, CCW_CMD_SENSE_ID, &vdev.senseid, sizeof(vdev.senseid))) {
+
+    /*
+     * Run sense id command.
+     * The size of the senseid data differs between devices (notably,
+     * between virtio devices and dasds), so specify the largest possible
+     * size and suppress the incorrect length indication for smaller sizes.
+     */
+    if (run_ccw(&vdev, CCW_CMD_SENSE_ID, &vdev.senseid, sizeof(vdev.senseid),
+                true)) {
         return false;
     }
     if (vdev.senseid.cu_type == 0x3832) {
@@ -343,20 +333,3 @@ bool virtio_is_supported(SubChannelId schid)
     }
     return false;
 }
-
-int enable_mss_facility(void)
-{
-    int ret;
-    ChscAreaSda *sda_area = (ChscAreaSda *) chsc_page;
-
-    memset(sda_area, 0, PAGE_SIZE);
-    sda_area->request.length = 0x0400;
-    sda_area->request.code = 0x0031;
-    sda_area->operation_code = 0x2;
-
-    ret = chsc(sda_area);
-    if ((ret == 0) && (sda_area->response.code == 0x0001)) {
-        return 0;
-    }
-    return -EIO;
-}
diff --git a/pc-bios/s390-netboot.img b/pc-bios/s390-netboot.img
index 2c6886e..aa90fbc 100644
--- a/pc-bios/s390-netboot.img
+++ b/pc-bios/s390-netboot.img
diff --git a/tests/boot-serial-test.c b/tests/boot-serial-test.c
index c591748..24852d4 100644
--- a/tests/boot-serial-test.c
+++ b/tests/boot-serial-test.c
@@ -114,7 +114,7 @@ static testdef_t tests[] = {
     { "sparc", "SS-4", "", "MB86904" },
     { "sparc", "SS-600MP", "", "TMS390Z55" },
     { "sparc64", "sun4u", "", "UltraSPARC" },
-    { "s390x", "s390-ccw-virtio", "", "virtio device" },
+    { "s390x", "s390-ccw-virtio", "", "device" },
     { "m68k", "mcf5208evb", "", "TT", sizeof(kernel_mcf5208), kernel_mcf5208 },
     { "microblaze", "petalogix-s3adsp1800", "", "TT",
       sizeof(kernel_pls3adsp1800), kernel_pls3adsp1800 },