diff --git a/target-s390x/Makefile.objs b/target-s390x/Makefile.objs
index e728abf..3afb0b7 100644
--- a/target-s390x/Makefile.objs
+++ b/target-s390x/Makefile.objs
@@ -1,4 +1,4 @@
 obj-y += translate.o helper.o cpu.o interrupt.o
 obj-y += int_helper.o fpu_helper.o cc_helper.o mem_helper.o misc_helper.o
-obj-$(CONFIG_SOFTMMU) += machine.o
+obj-$(CONFIG_SOFTMMU) += machine.o ioinst.o
 obj-$(CONFIG_KVM) += kvm.o
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index cd729d3..931ed4d 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -352,6 +352,11 @@ static inline unsigned s390_del_running_cpu(CPUS390XState *env)
 void cpu_lock(void);
 void cpu_unlock(void);
 
+typedef struct SCHIB SCHIB;
+typedef struct ORB ORB;
+typedef struct IRB IRB;
+typedef struct CRW CRW;
+
 static inline void cpu_set_tls(CPUS390XState *env, target_ulong newtls)
 {
     env->aregs[0] = newtls >> 32;
diff --git a/target-s390x/ioinst.c b/target-s390x/ioinst.c
new file mode 100644
index 0000000..06a16ee
--- /dev/null
+++ b/target-s390x/ioinst.c
@@ -0,0 +1,36 @@
+/*
+ * I/O instructions for S/390
+ *
+ * Copyright 2012 IBM Corp.
+ * Author(s): Cornelia Huck <cornelia.huck@de.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 <sys/types.h>
+
+#include "cpu.h"
+#include "ioinst.h"
+
+int ioinst_disassemble_sch_ident(uint32_t value, int *m, int *cssid, int *ssid,
+                                 int *schid)
+{
+    if (!IOINST_SCHID_ONE(value)) {
+        return -EINVAL;
+    }
+    if (!IOINST_SCHID_M(value)) {
+        if (IOINST_SCHID_CSSID(value)) {
+            return -EINVAL;
+        }
+        *cssid = 0;
+        *m = 0;
+    } else {
+        *cssid = IOINST_SCHID_CSSID(value);
+        *m = 1;
+    }
+    *ssid = IOINST_SCHID_SSID(value);
+    *schid = IOINST_SCHID_NR(value);
+    return 0;
+}
diff --git a/target-s390x/ioinst.h b/target-s390x/ioinst.h
new file mode 100644
index 0000000..5580d91
--- /dev/null
+++ b/target-s390x/ioinst.h
@@ -0,0 +1,207 @@
+/*
+ * S/390 channel I/O instructions
+ *
+ * Copyright 2012 IBM Corp.
+ * Author(s): Cornelia Huck <cornelia.huck@de.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 IOINST_S390X_H
+#define IOINST_S390X_H
+/*
+ * Channel I/O related definitions, as defined in the Principles
+ * Of Operation (and taken from the Linux implementation).
+ */
+
+/* subchannel status word (command mode only) */
+typedef struct SCSW {
+    uint16_t flags;
+    uint16_t ctrl;
+    uint32_t cpa;
+    uint8_t dstat;
+    uint8_t cstat;
+    uint16_t count;
+} QEMU_PACKED SCSW;
+
+#define SCSW_FLAGS_MASK_KEY 0xf000
+#define SCSW_FLAGS_MASK_SCTL 0x0800
+#define SCSW_FLAGS_MASK_ESWF 0x0400
+#define SCSW_FLAGS_MASK_CC 0x0300
+#define SCSW_FLAGS_MASK_FMT 0x0080
+#define SCSW_FLAGS_MASK_PFCH 0x0040
+#define SCSW_FLAGS_MASK_ISIC 0x0020
+#define SCSW_FLAGS_MASK_ALCC 0x0010
+#define SCSW_FLAGS_MASK_SSI 0x0008
+#define SCSW_FLAGS_MASK_ZCC 0x0004
+#define SCSW_FLAGS_MASK_ECTL 0x0002
+#define SCSW_FLAGS_MASK_PNO 0x0001
+
+#define SCSW_CTRL_MASK_FCTL 0x7000
+#define SCSW_CTRL_MASK_ACTL 0x0fe0
+#define SCSW_CTRL_MASK_STCTL 0x001f
+
+#define SCSW_FCTL_CLEAR_FUNC 0x1000
+#define SCSW_FCTL_HALT_FUNC 0x2000
+#define SCSW_FCTL_START_FUNC 0x4000
+
+#define SCSW_ACTL_SUSP 0x0020
+#define SCSW_ACTL_DEVICE_ACTIVE 0x0040
+#define SCSW_ACTL_SUBCH_ACTIVE 0x0080
+#define SCSW_ACTL_CLEAR_PEND 0x0100
+#define SCSW_ACTL_HALT_PEND  0x0200
+#define SCSW_ACTL_START_PEND 0x0400
+#define SCSW_ACTL_RESUME_PEND 0x0800
+
+#define SCSW_STCTL_STATUS_PEND 0x0001
+#define SCSW_STCTL_SECONDARY 0x0002
+#define SCSW_STCTL_PRIMARY 0x0004
+#define SCSW_STCTL_INTERMEDIATE 0x0008
+#define SCSW_STCTL_ALERT 0x0010
+
+#define SCSW_DSTAT_ATTENTION     0x80
+#define SCSW_DSTAT_STAT_MOD      0x40
+#define SCSW_DSTAT_CU_END        0x20
+#define SCSW_DSTAT_BUSY          0x10
+#define SCSW_DSTAT_CHANNEL_END   0x08
+#define SCSW_DSTAT_DEVICE_END    0x04
+#define SCSW_DSTAT_UNIT_CHECK    0x02
+#define SCSW_DSTAT_UNIT_EXCEP    0x01
+
+#define SCSW_CSTAT_PCI           0x80
+#define SCSW_CSTAT_INCORR_LEN    0x40
+#define SCSW_CSTAT_PROG_CHECK    0x20
+#define SCSW_CSTAT_PROT_CHECK    0x10
+#define SCSW_CSTAT_DATA_CHECK    0x08
+#define SCSW_CSTAT_CHN_CTRL_CHK  0x04
+#define SCSW_CSTAT_INTF_CTRL_CHK 0x02
+#define SCSW_CSTAT_CHAIN_CHECK   0x01
+
+/* path management control word */
+typedef struct PMCW {
+    uint32_t intparm;
+    uint16_t flags;
+    uint16_t devno;
+    uint8_t  lpm;
+    uint8_t  pnom;
+    uint8_t  lpum;
+    uint8_t  pim;
+    uint16_t mbi;
+    uint8_t  pom;
+    uint8_t  pam;
+    uint8_t  chpid[8];
+    uint32_t chars;
+} QEMU_PACKED PMCW;
+
+#define PMCW_FLAGS_MASK_QF 0x8000
+#define PMCW_FLAGS_MASK_W 0x4000
+#define PMCW_FLAGS_MASK_ISC 0x3800
+#define PMCW_FLAGS_MASK_ENA 0x0080
+#define PMCW_FLAGS_MASK_LM 0x0060
+#define PMCW_FLAGS_MASK_MME 0x0018
+#define PMCW_FLAGS_MASK_MP 0x0004
+#define PMCW_FLAGS_MASK_TF 0x0002
+#define PMCW_FLAGS_MASK_DNV 0x0001
+#define PMCW_FLAGS_MASK_INVALID 0x0700
+
+#define PMCW_CHARS_MASK_ST 0x00e00000
+#define PMCW_CHARS_MASK_MBFC 0x00000004
+#define PMCW_CHARS_MASK_XMWME 0x00000002
+#define PMCW_CHARS_MASK_CSENSE 0x00000001
+#define PMCW_CHARS_MASK_INVALID 0xff1ffff8
+
+/* subchannel information block */
+struct SCHIB {
+    PMCW pmcw;
+    SCSW scsw;
+    uint64_t mba;
+    uint8_t mda[4];
+} QEMU_PACKED;
+
+/* interruption response block */
+struct IRB {
+    SCSW scsw;
+    uint32_t esw[5];
+    uint32_t ecw[8];
+    uint32_t emw[8];
+} QEMU_PACKED;
+
+/* operation request block */
+struct ORB {
+    uint32_t intparm;
+    uint16_t ctrl0;
+    uint8_t lpm;
+    uint8_t ctrl1;
+    uint32_t cpa;
+} QEMU_PACKED;
+
+#define ORB_CTRL0_MASK_KEY 0xf000
+#define ORB_CTRL0_MASK_SPND 0x0800
+#define ORB_CTRL0_MASK_STR 0x0400
+#define ORB_CTRL0_MASK_MOD 0x0200
+#define ORB_CTRL0_MASK_SYNC 0x0100
+#define ORB_CTRL0_MASK_FMT 0x0080
+#define ORB_CTRL0_MASK_PFCH 0x0040
+#define ORB_CTRL0_MASK_ISIC 0x0020
+#define ORB_CTRL0_MASK_ALCC 0x0010
+#define ORB_CTRL0_MASK_SSIC 0x0008
+#define ORB_CTRL0_MASK_C64 0x0002
+#define ORB_CTRL0_MASK_I2K 0x0001
+#define ORB_CTRL0_MASK_INVALID 0x0004
+
+#define ORB_CTRL1_MASK_ILS 0x80
+#define ORB_CTRL1_MASK_MIDAW 0x40
+#define ORB_CTRL1_MASK_ORBX 0x01
+#define ORB_CTRL1_MASK_INVALID 0x3e
+
+/* channel command word (type 1) */
+typedef struct CCW1 {
+    uint8_t cmd_code;
+    uint8_t flags;
+    uint16_t count;
+    uint32_t cda;
+} QEMU_PACKED CCW1;
+
+#define CCW_FLAG_DC              0x80
+#define CCW_FLAG_CC              0x40
+#define CCW_FLAG_SLI             0x20
+#define CCW_FLAG_SKIP            0x10
+#define CCW_FLAG_PCI             0x08
+#define CCW_FLAG_IDA             0x04
+#define CCW_FLAG_SUSPEND         0x02
+
+#define CCW_CMD_NOOP             0x03
+#define CCW_CMD_BASIC_SENSE      0x04
+#define CCW_CMD_TIC              0x08
+#define CCW_CMD_SENSE_ID         0xe4
+
+struct CRW {
+    uint16_t flags;
+    uint16_t rsid;
+} QEMU_PACKED;
+
+#define CRW_FLAGS_MASK_S 0x4000
+#define CRW_FLAGS_MASK_R 0x2000
+#define CRW_FLAGS_MASK_C 0x1000
+#define CRW_FLAGS_MASK_RSC 0x0f00
+#define CRW_FLAGS_MASK_A 0x0080
+#define CRW_FLAGS_MASK_ERC 0x003f
+
+#define CRW_ERC_INIT 0x02
+#define CRW_ERC_IPI  0x04
+
+#define CRW_RSC_SUBCH 0x3
+#define CRW_RSC_CHP   0x4
+
+/* schid disintegration */
+#define IOINST_SCHID_ONE(_schid)   ((_schid & 0x00010000) >> 16)
+#define IOINST_SCHID_M(_schid)     ((_schid & 0x00080000) >> 19)
+#define IOINST_SCHID_CSSID(_schid) ((_schid & 0xff000000) >> 24)
+#define IOINST_SCHID_SSID(_schid)  ((_schid & 0x00060000) >> 17)
+#define IOINST_SCHID_NR(_schid)    (_schid & 0x0000ffff)
+
+int ioinst_disassemble_sch_ident(uint32_t value, int *m, int *cssid, int *ssid,
+                                 int *schid);
+#endif
