Patchwork [07/15] s390: Virtual channel subsystem support.

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Submitter Alexander Graf
Date Jan. 25, 2013, 12:48 p.m.
Message ID <1359118138-9367-8-git-send-email-agraf@suse.de>
Download mbox | patch
Permalink /patch/215686/
State New
Headers show

Comments

Alexander Graf - Jan. 25, 2013, 12:48 p.m.
From: Cornelia Huck <cornelia.huck@de.ibm.com>

Provide a mechanism for qemu to provide fully virtual subchannels to
the guest.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 hw/s390x/Makefile.objs |    1 +
 hw/s390x/css.c         | 1277 ++++++++++++++++++++++++++++++++++++++++++++++++
 hw/s390x/css.h         |   99 ++++
 target-s390x/cpu.h     |   62 +++
 trace-events           |    8 +
 5 files changed, 1447 insertions(+), 0 deletions(-)
 create mode 100644 hw/s390x/css.c
 create mode 100644 hw/s390x/css.h

Patch

diff --git a/hw/s390x/Makefile.objs b/hw/s390x/Makefile.objs
index 1b40c2e..ab99da6 100644
--- a/hw/s390x/Makefile.objs
+++ b/hw/s390x/Makefile.objs
@@ -6,3 +6,4 @@  obj-y += sclp.o
 obj-y += event-facility.o
 obj-y += sclpquiesce.o sclpconsole.o
 obj-y += ipl.o
+obj-y += css.o
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
new file mode 100644
index 0000000..113ac9a
--- /dev/null
+++ b/hw/s390x/css.c
@@ -0,0 +1,1277 @@ 
+/*
+ * Channel subsystem base support.
+ *
+ * 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 <hw/qdev.h>
+#include "qemu/bitops.h"
+#include "cpu.h"
+#include "ioinst.h"
+#include "css.h"
+#include "trace.h"
+
+typedef struct CrwContainer {
+    CRW crw;
+    QTAILQ_ENTRY(CrwContainer) sibling;
+} CrwContainer;
+
+typedef struct ChpInfo {
+    uint8_t in_use;
+    uint8_t type;
+    uint8_t is_virtual;
+} ChpInfo;
+
+typedef struct SubchSet {
+    SubchDev *sch[MAX_SCHID + 1];
+    unsigned long schids_used[BITS_TO_LONGS(MAX_SCHID + 1)];
+    unsigned long devnos_used[BITS_TO_LONGS(MAX_SCHID + 1)];
+} SubchSet;
+
+typedef struct CssImage {
+    SubchSet *sch_set[MAX_SSID + 1];
+    ChpInfo chpids[MAX_CHPID + 1];
+} CssImage;
+
+typedef struct ChannelSubSys {
+    QTAILQ_HEAD(, CrwContainer) pending_crws;
+    bool do_crw_mchk;
+    bool crws_lost;
+    uint8_t max_cssid;
+    uint8_t max_ssid;
+    bool chnmon_active;
+    uint64_t chnmon_area;
+    CssImage *css[MAX_CSSID + 1];
+    uint8_t default_cssid;
+} ChannelSubSys;
+
+static ChannelSubSys *channel_subsys;
+
+int css_create_css_image(uint8_t cssid, bool default_image)
+{
+    trace_css_new_image(cssid, default_image ? "(default)" : "");
+    if (cssid > MAX_CSSID) {
+        return -EINVAL;
+    }
+    if (channel_subsys->css[cssid]) {
+        return -EBUSY;
+    }
+    channel_subsys->css[cssid] = g_malloc0(sizeof(CssImage));
+    if (default_image) {
+        channel_subsys->default_cssid = cssid;
+    }
+    return 0;
+}
+
+static uint16_t css_build_subchannel_id(SubchDev *sch)
+{
+    if (channel_subsys->max_cssid > 0) {
+        return (sch->cssid << 8) | (1 << 3) | (sch->ssid << 1) | 1;
+    }
+    return (sch->ssid << 1) | 1;
+}
+
+static void css_inject_io_interrupt(SubchDev *sch)
+{
+    S390CPU *cpu = s390_cpu_addr2state(0);
+    uint8_t isc = (sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_ISC) >> 11;
+
+    trace_css_io_interrupt(sch->cssid, sch->ssid, sch->schid,
+                           sch->curr_status.pmcw.intparm, isc, "");
+    s390_io_interrupt(cpu,
+                      css_build_subchannel_id(sch),
+                      sch->schid,
+                      sch->curr_status.pmcw.intparm,
+                      (0x80 >> isc) << 24);
+}
+
+void css_conditional_io_interrupt(SubchDev *sch)
+{
+    /*
+     * If the subchannel is not currently status pending, make it pending
+     * with alert status.
+     */
+    if (!(sch->curr_status.scsw.ctrl & SCSW_STCTL_STATUS_PEND)) {
+        S390CPU *cpu = s390_cpu_addr2state(0);
+        uint8_t isc = (sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_ISC) >> 11;
+
+        trace_css_io_interrupt(sch->cssid, sch->ssid, sch->schid,
+                               sch->curr_status.pmcw.intparm, isc,
+                               "(unsolicited)");
+        sch->curr_status.scsw.ctrl &= ~SCSW_CTRL_MASK_STCTL;
+        sch->curr_status.scsw.ctrl |=
+            SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+        /* Inject an I/O interrupt. */
+        s390_io_interrupt(cpu,
+                          css_build_subchannel_id(sch),
+                          sch->schid,
+                          sch->curr_status.pmcw.intparm,
+                          (0x80 >> isc) << 24);
+    }
+}
+
+static void sch_handle_clear_func(SubchDev *sch)
+{
+    PMCW *p = &sch->curr_status.pmcw;
+    SCSW *s = &sch->curr_status.scsw;
+    int path;
+
+    /* Path management: In our simple css, we always choose the only path. */
+    path = 0x80;
+
+    /* Reset values prior to 'issueing the clear signal'. */
+    p->lpum = 0;
+    p->pom = 0xff;
+    s->flags &= ~SCSW_FLAGS_MASK_PNO;
+
+    /* We always 'attempt to issue the clear signal', and we always succeed. */
+    sch->orb = NULL;
+    sch->channel_prog = 0x0;
+    sch->last_cmd_valid = false;
+    s->ctrl &= ~SCSW_ACTL_CLEAR_PEND;
+    s->ctrl |= SCSW_STCTL_STATUS_PEND;
+
+    s->dstat = 0;
+    s->cstat = 0;
+    p->lpum = path;
+
+}
+
+static void sch_handle_halt_func(SubchDev *sch)
+{
+
+    PMCW *p = &sch->curr_status.pmcw;
+    SCSW *s = &sch->curr_status.scsw;
+    int path;
+
+    /* Path management: In our simple css, we always choose the only path. */
+    path = 0x80;
+
+    /* We always 'attempt to issue the halt signal', and we always succeed. */
+    sch->orb = NULL;
+    sch->channel_prog = 0x0;
+    sch->last_cmd_valid = false;
+    s->ctrl &= ~SCSW_ACTL_HALT_PEND;
+    s->ctrl |= SCSW_STCTL_STATUS_PEND;
+
+    if ((s->ctrl & (SCSW_ACTL_SUBCH_ACTIVE | SCSW_ACTL_DEVICE_ACTIVE)) ||
+        !((s->ctrl & SCSW_ACTL_START_PEND) ||
+          (s->ctrl & SCSW_ACTL_SUSP))) {
+        s->dstat = SCSW_DSTAT_DEVICE_END;
+    }
+    s->cstat = 0;
+    p->lpum = path;
+
+}
+
+static void copy_sense_id_to_guest(SenseId *dest, SenseId *src)
+{
+    int i;
+
+    dest->reserved = src->reserved;
+    dest->cu_type = cpu_to_be16(src->cu_type);
+    dest->cu_model = src->cu_model;
+    dest->dev_type = cpu_to_be16(src->dev_type);
+    dest->dev_model = src->dev_model;
+    dest->unused = src->unused;
+    for (i = 0; i < ARRAY_SIZE(dest->ciw); i++) {
+        dest->ciw[i].type = src->ciw[i].type;
+        dest->ciw[i].command = src->ciw[i].command;
+        dest->ciw[i].count = cpu_to_be16(src->ciw[i].count);
+    }
+}
+
+static CCW1 copy_ccw_from_guest(hwaddr addr)
+{
+    CCW1 tmp;
+    CCW1 ret;
+
+    cpu_physical_memory_read(addr, &tmp, sizeof(tmp));
+    ret.cmd_code = tmp.cmd_code;
+    ret.flags = tmp.flags;
+    ret.count = be16_to_cpu(tmp.count);
+    ret.cda = be32_to_cpu(tmp.cda);
+
+    return ret;
+}
+
+static int css_interpret_ccw(SubchDev *sch, hwaddr ccw_addr)
+{
+    int ret;
+    bool check_len;
+    int len;
+    CCW1 ccw;
+
+    if (!ccw_addr) {
+        return -EIO;
+    }
+
+    ccw = copy_ccw_from_guest(ccw_addr);
+
+    /* Check for invalid command codes. */
+    if ((ccw.cmd_code & 0x0f) == 0) {
+        return -EINVAL;
+    }
+    if (((ccw.cmd_code & 0x0f) == CCW_CMD_TIC) &&
+        ((ccw.cmd_code & 0xf0) != 0)) {
+        return -EINVAL;
+    }
+
+    if (ccw.flags & CCW_FLAG_SUSPEND) {
+        return -ERESTART;
+    }
+
+    check_len = !((ccw.flags & CCW_FLAG_SLI) && !(ccw.flags & CCW_FLAG_DC));
+
+    /* Look at the command. */
+    switch (ccw.cmd_code) {
+    case CCW_CMD_NOOP:
+        /* Nothing to do. */
+        ret = 0;
+        break;
+    case CCW_CMD_BASIC_SENSE:
+        if (check_len) {
+            if (ccw.count != sizeof(sch->sense_data)) {
+                ret = -EINVAL;
+                break;
+            }
+        }
+        len = MIN(ccw.count, sizeof(sch->sense_data));
+        cpu_physical_memory_write(ccw.cda, sch->sense_data, len);
+        sch->curr_status.scsw.count = ccw.count - len;
+        memset(sch->sense_data, 0, sizeof(sch->sense_data));
+        ret = 0;
+        break;
+    case CCW_CMD_SENSE_ID:
+    {
+        SenseId sense_id;
+
+        copy_sense_id_to_guest(&sense_id, &sch->id);
+        /* Sense ID information is device specific. */
+        if (check_len) {
+            if (ccw.count != sizeof(sense_id)) {
+                ret = -EINVAL;
+                break;
+            }
+        }
+        len = MIN(ccw.count, sizeof(sense_id));
+        /*
+         * Only indicate 0xff in the first sense byte if we actually
+         * have enough place to store at least bytes 0-3.
+         */
+        if (len >= 4) {
+            sense_id.reserved = 0xff;
+        } else {
+            sense_id.reserved = 0;
+        }
+        cpu_physical_memory_write(ccw.cda, &sense_id, len);
+        sch->curr_status.scsw.count = ccw.count - len;
+        ret = 0;
+        break;
+    }
+    case CCW_CMD_TIC:
+        if (sch->last_cmd_valid && (sch->last_cmd.cmd_code == CCW_CMD_TIC)) {
+            ret = -EINVAL;
+            break;
+        }
+        if (ccw.flags & (CCW_FLAG_CC | CCW_FLAG_DC)) {
+            ret = -EINVAL;
+            break;
+        }
+        sch->channel_prog = ccw.cda;
+        ret = -EAGAIN;
+        break;
+    default:
+        if (sch->ccw_cb) {
+            /* Handle device specific commands. */
+            ret = sch->ccw_cb(sch, ccw);
+        } else {
+            ret = -EOPNOTSUPP;
+        }
+        break;
+    }
+    sch->last_cmd = ccw;
+    sch->last_cmd_valid = true;
+    if (ret == 0) {
+        if (ccw.flags & CCW_FLAG_CC) {
+            sch->channel_prog += 8;
+            ret = -EAGAIN;
+        }
+    }
+
+    return ret;
+}
+
+static void sch_handle_start_func(SubchDev *sch)
+{
+
+    PMCW *p = &sch->curr_status.pmcw;
+    SCSW *s = &sch->curr_status.scsw;
+    ORB *orb = sch->orb;
+    int path;
+    int ret;
+
+    /* Path management: In our simple css, we always choose the only path. */
+    path = 0x80;
+
+    if (!(s->ctrl & SCSW_ACTL_SUSP)) {
+        /* Look at the orb and try to execute the channel program. */
+        p->intparm = orb->intparm;
+        if (!(orb->lpm & path)) {
+            /* Generate a deferred cc 3 condition. */
+            s->flags |= SCSW_FLAGS_MASK_CC;
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= (SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND);
+            return;
+        }
+    } else {
+        s->ctrl &= ~(SCSW_ACTL_SUSP | SCSW_ACTL_RESUME_PEND);
+    }
+    sch->last_cmd_valid = false;
+    do {
+        ret = css_interpret_ccw(sch, sch->channel_prog);
+        switch (ret) {
+        case -EAGAIN:
+            /* ccw chain, continue processing */
+            break;
+        case 0:
+            /* success */
+            s->ctrl &= ~SCSW_ACTL_START_PEND;
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
+                    SCSW_STCTL_STATUS_PEND;
+            s->dstat = SCSW_DSTAT_CHANNEL_END | SCSW_DSTAT_DEVICE_END;
+            break;
+        case -EOPNOTSUPP:
+            /* unsupported command, generate unit check (command reject) */
+            s->ctrl &= ~SCSW_ACTL_START_PEND;
+            s->dstat = SCSW_DSTAT_UNIT_CHECK;
+            /* Set sense bit 0 in ecw0. */
+            sch->sense_data[0] = 0x80;
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
+                    SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+            break;
+        case -EFAULT:
+            /* memory problem, generate channel data check */
+            s->ctrl &= ~SCSW_ACTL_START_PEND;
+            s->cstat = SCSW_CSTAT_DATA_CHECK;
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
+                    SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+            break;
+        case -EBUSY:
+            /* subchannel busy, generate deferred cc 1 */
+            s->flags &= ~SCSW_FLAGS_MASK_CC;
+            s->flags |= (1 << 8);
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+            break;
+        case -ERESTART:
+            /* channel program has been suspended */
+            s->ctrl &= ~SCSW_ACTL_START_PEND;
+            s->ctrl |= SCSW_ACTL_SUSP;
+            break;
+        default:
+            /* error, generate channel program check */
+            s->ctrl &= ~SCSW_ACTL_START_PEND;
+            s->cstat = SCSW_CSTAT_PROG_CHECK;
+            s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+            s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
+                    SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;
+            break;
+        }
+    } while (ret == -EAGAIN);
+
+}
+
+/*
+ * On real machines, this would run asynchronously to the main vcpus.
+ * We might want to make some parts of the ssch handling (interpreting
+ * read/writes) asynchronous later on if we start supporting more than
+ * our current very simple devices.
+ */
+static void do_subchannel_work(SubchDev *sch)
+{
+
+    SCSW *s = &sch->curr_status.scsw;
+
+    if (s->ctrl & SCSW_FCTL_CLEAR_FUNC) {
+        sch_handle_clear_func(sch);
+    } else if (s->ctrl & SCSW_FCTL_HALT_FUNC) {
+        sch_handle_halt_func(sch);
+    } else if (s->ctrl & SCSW_FCTL_START_FUNC) {
+        sch_handle_start_func(sch);
+    } else {
+        /* Cannot happen. */
+        return;
+    }
+    css_inject_io_interrupt(sch);
+}
+
+static void copy_pmcw_to_guest(PMCW *dest, const PMCW *src)
+{
+    int i;
+
+    dest->intparm = cpu_to_be32(src->intparm);
+    dest->flags = cpu_to_be16(src->flags);
+    dest->devno = cpu_to_be16(src->devno);
+    dest->lpm = src->lpm;
+    dest->pnom = src->pnom;
+    dest->lpum = src->lpum;
+    dest->pim = src->pim;
+    dest->mbi = cpu_to_be16(src->mbi);
+    dest->pom = src->pom;
+    dest->pam = src->pam;
+    for (i = 0; i < ARRAY_SIZE(dest->chpid); i++) {
+        dest->chpid[i] = src->chpid[i];
+    }
+    dest->chars = cpu_to_be32(src->chars);
+}
+
+static void copy_scsw_to_guest(SCSW *dest, const SCSW *src)
+{
+    dest->flags = cpu_to_be16(src->flags);
+    dest->ctrl = cpu_to_be16(src->ctrl);
+    dest->cpa = cpu_to_be32(src->cpa);
+    dest->dstat = src->dstat;
+    dest->cstat = src->cstat;
+    dest->count = cpu_to_be16(src->count);
+}
+
+static void copy_schib_to_guest(SCHIB *dest, const SCHIB *src)
+{
+    int i;
+
+    copy_pmcw_to_guest(&dest->pmcw, &src->pmcw);
+    copy_scsw_to_guest(&dest->scsw, &src->scsw);
+    dest->mba = cpu_to_be64(src->mba);
+    for (i = 0; i < ARRAY_SIZE(dest->mda); i++) {
+        dest->mda[i] = src->mda[i];
+    }
+}
+
+int css_do_stsch(SubchDev *sch, SCHIB *schib)
+{
+    /* Use current status. */
+    copy_schib_to_guest(schib, &sch->curr_status);
+    return 0;
+}
+
+static void copy_pmcw_from_guest(PMCW *dest, const PMCW *src)
+{
+    int i;
+
+    dest->intparm = be32_to_cpu(src->intparm);
+    dest->flags = be16_to_cpu(src->flags);
+    dest->devno = be16_to_cpu(src->devno);
+    dest->lpm = src->lpm;
+    dest->pnom = src->pnom;
+    dest->lpum = src->lpum;
+    dest->pim = src->pim;
+    dest->mbi = be16_to_cpu(src->mbi);
+    dest->pom = src->pom;
+    dest->pam = src->pam;
+    for (i = 0; i < ARRAY_SIZE(dest->chpid); i++) {
+        dest->chpid[i] = src->chpid[i];
+    }
+    dest->chars = be32_to_cpu(src->chars);
+}
+
+static void copy_scsw_from_guest(SCSW *dest, const SCSW *src)
+{
+    dest->flags = be16_to_cpu(src->flags);
+    dest->ctrl = be16_to_cpu(src->ctrl);
+    dest->cpa = be32_to_cpu(src->cpa);
+    dest->dstat = src->dstat;
+    dest->cstat = src->cstat;
+    dest->count = be16_to_cpu(src->count);
+}
+
+static void copy_schib_from_guest(SCHIB *dest, const SCHIB *src)
+{
+    int i;
+
+    copy_pmcw_from_guest(&dest->pmcw, &src->pmcw);
+    copy_scsw_from_guest(&dest->scsw, &src->scsw);
+    dest->mba = be64_to_cpu(src->mba);
+    for (i = 0; i < ARRAY_SIZE(dest->mda); i++) {
+        dest->mda[i] = src->mda[i];
+    }
+}
+
+int css_do_msch(SubchDev *sch, SCHIB *orig_schib)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+    SCHIB schib;
+
+    if (!(sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_DNV)) {
+        ret = 0;
+        goto out;
+    }
+
+    if (s->ctrl & SCSW_STCTL_STATUS_PEND) {
+        ret = -EINPROGRESS;
+        goto out;
+    }
+
+    if (s->ctrl &
+        (SCSW_FCTL_START_FUNC|SCSW_FCTL_HALT_FUNC|SCSW_FCTL_CLEAR_FUNC)) {
+        ret = -EBUSY;
+        goto out;
+    }
+
+    copy_schib_from_guest(&schib, orig_schib);
+    /* Only update the program-modifiable fields. */
+    p->intparm = schib.pmcw.intparm;
+    p->flags &= ~(PMCW_FLAGS_MASK_ISC | PMCW_FLAGS_MASK_ENA |
+                  PMCW_FLAGS_MASK_LM | PMCW_FLAGS_MASK_MME |
+                  PMCW_FLAGS_MASK_MP);
+    p->flags |= schib.pmcw.flags &
+            (PMCW_FLAGS_MASK_ISC | PMCW_FLAGS_MASK_ENA |
+             PMCW_FLAGS_MASK_LM | PMCW_FLAGS_MASK_MME |
+             PMCW_FLAGS_MASK_MP);
+    p->lpm = schib.pmcw.lpm;
+    p->mbi = schib.pmcw.mbi;
+    p->pom = schib.pmcw.pom;
+    p->chars &= ~(PMCW_CHARS_MASK_MBFC | PMCW_CHARS_MASK_CSENSE);
+    p->chars |= schib.pmcw.chars &
+            (PMCW_CHARS_MASK_MBFC | PMCW_CHARS_MASK_CSENSE);
+    sch->curr_status.mba = schib.mba;
+
+    ret = 0;
+
+out:
+    return ret;
+}
+
+int css_do_xsch(SubchDev *sch)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    if (!(s->ctrl & SCSW_CTRL_MASK_FCTL) ||
+        ((s->ctrl & SCSW_CTRL_MASK_FCTL) != SCSW_FCTL_START_FUNC) ||
+        (!(s->ctrl &
+           (SCSW_ACTL_RESUME_PEND | SCSW_ACTL_START_PEND | SCSW_ACTL_SUSP))) ||
+        (s->ctrl & SCSW_ACTL_SUBCH_ACTIVE)) {
+        ret = -EINPROGRESS;
+        goto out;
+    }
+
+    if (s->ctrl & SCSW_CTRL_MASK_STCTL) {
+        ret = -EBUSY;
+        goto out;
+    }
+
+    /* Cancel the current operation. */
+    s->ctrl &= ~(SCSW_FCTL_START_FUNC |
+                 SCSW_ACTL_RESUME_PEND |
+                 SCSW_ACTL_START_PEND |
+                 SCSW_ACTL_SUSP);
+    sch->channel_prog = 0x0;
+    sch->last_cmd_valid = false;
+    sch->orb = NULL;
+    s->dstat = 0;
+    s->cstat = 0;
+    ret = 0;
+
+out:
+    return ret;
+}
+
+int css_do_csch(SubchDev *sch)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    /* Trigger the clear function. */
+    s->ctrl &= ~(SCSW_CTRL_MASK_FCTL | SCSW_CTRL_MASK_ACTL);
+    s->ctrl |= SCSW_FCTL_CLEAR_FUNC | SCSW_FCTL_CLEAR_FUNC;
+
+    do_subchannel_work(sch);
+    ret = 0;
+
+out:
+    return ret;
+}
+
+int css_do_hsch(SubchDev *sch)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    if (((s->ctrl & SCSW_CTRL_MASK_STCTL) == SCSW_STCTL_STATUS_PEND) ||
+        (s->ctrl & (SCSW_STCTL_PRIMARY |
+                    SCSW_STCTL_SECONDARY |
+                    SCSW_STCTL_ALERT))) {
+        ret = -EINPROGRESS;
+        goto out;
+    }
+
+    if (s->ctrl & (SCSW_FCTL_HALT_FUNC | SCSW_FCTL_CLEAR_FUNC)) {
+        ret = -EBUSY;
+        goto out;
+    }
+
+    /* Trigger the halt function. */
+    s->ctrl |= SCSW_FCTL_HALT_FUNC;
+    s->ctrl &= ~SCSW_FCTL_START_FUNC;
+    if (((s->ctrl & SCSW_CTRL_MASK_ACTL) ==
+         (SCSW_ACTL_SUBCH_ACTIVE | SCSW_ACTL_DEVICE_ACTIVE)) &&
+        ((s->ctrl & SCSW_CTRL_MASK_STCTL) == SCSW_STCTL_INTERMEDIATE)) {
+        s->ctrl &= ~SCSW_STCTL_STATUS_PEND;
+    }
+    s->ctrl |= SCSW_ACTL_HALT_PEND;
+
+    do_subchannel_work(sch);
+    ret = 0;
+
+out:
+    return ret;
+}
+
+static void css_update_chnmon(SubchDev *sch)
+{
+    if (!(sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_MME)) {
+        /* Not active. */
+        return;
+    }
+    /* The counter is conveniently located at the beginning of the struct. */
+    if (sch->curr_status.pmcw.chars & PMCW_CHARS_MASK_MBFC) {
+        /* Format 1, per-subchannel area. */
+        uint32_t count;
+
+        count = ldl_phys(sch->curr_status.mba);
+        count++;
+        stl_phys(sch->curr_status.mba, count);
+    } else {
+        /* Format 0, global area. */
+        uint32_t offset;
+        uint16_t count;
+
+        offset = sch->curr_status.pmcw.mbi << 5;
+        count = lduw_phys(channel_subsys->chnmon_area + offset);
+        count++;
+        stw_phys(channel_subsys->chnmon_area + offset, count);
+    }
+}
+
+int css_do_ssch(SubchDev *sch, ORB *orb)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    if (s->ctrl & SCSW_STCTL_STATUS_PEND) {
+        ret = -EINPROGRESS;
+        goto out;
+    }
+
+    if (s->ctrl & (SCSW_FCTL_START_FUNC |
+                   SCSW_FCTL_HALT_FUNC |
+                   SCSW_FCTL_CLEAR_FUNC)) {
+        ret = -EBUSY;
+        goto out;
+    }
+
+    /* If monitoring is active, update counter. */
+    if (channel_subsys->chnmon_active) {
+        css_update_chnmon(sch);
+    }
+    sch->orb = orb;
+    sch->channel_prog = orb->cpa;
+    /* Trigger the start function. */
+    s->ctrl |= (SCSW_FCTL_START_FUNC | SCSW_ACTL_START_PEND);
+    s->flags &= ~SCSW_FLAGS_MASK_PNO;
+
+    do_subchannel_work(sch);
+    ret = 0;
+
+out:
+    return ret;
+}
+
+static void copy_irb_to_guest(IRB *dest, const IRB *src)
+{
+    int i;
+
+    copy_scsw_to_guest(&dest->scsw, &src->scsw);
+
+    for (i = 0; i < ARRAY_SIZE(dest->esw); i++) {
+        dest->esw[i] = cpu_to_be32(src->esw[i]);
+    }
+    for (i = 0; i < ARRAY_SIZE(dest->ecw); i++) {
+        dest->ecw[i] = cpu_to_be32(src->ecw[i]);
+    }
+    for (i = 0; i < ARRAY_SIZE(dest->emw); i++) {
+        dest->emw[i] = cpu_to_be32(src->emw[i]);
+    }
+}
+
+int css_do_tsch(SubchDev *sch, IRB *target_irb)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    uint16_t stctl;
+    uint16_t fctl;
+    uint16_t actl;
+    IRB irb;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = 3;
+        goto out;
+    }
+
+    stctl = s->ctrl & SCSW_CTRL_MASK_STCTL;
+    fctl = s->ctrl & SCSW_CTRL_MASK_FCTL;
+    actl = s->ctrl & SCSW_CTRL_MASK_ACTL;
+
+    /* Prepare the irb for the guest. */
+    memset(&irb, 0, sizeof(IRB));
+
+    /* Copy scsw from current status. */
+    memcpy(&irb.scsw, s, sizeof(SCSW));
+    if (stctl & SCSW_STCTL_STATUS_PEND) {
+        if (s->cstat & (SCSW_CSTAT_DATA_CHECK |
+                        SCSW_CSTAT_CHN_CTRL_CHK |
+                        SCSW_CSTAT_INTF_CTRL_CHK)) {
+            irb.scsw.flags |= SCSW_FLAGS_MASK_ESWF;
+            irb.esw[0] = 0x04804000;
+        } else {
+            irb.esw[0] = 0x00800000;
+        }
+        /* If a unit check is pending, copy sense data. */
+        if ((s->dstat & SCSW_DSTAT_UNIT_CHECK) &&
+            (p->chars & PMCW_CHARS_MASK_CSENSE)) {
+            irb.scsw.flags |= SCSW_FLAGS_MASK_ESWF | SCSW_FLAGS_MASK_ECTL;
+            memcpy(irb.ecw, sch->sense_data, sizeof(sch->sense_data));
+            irb.esw[1] = 0x02000000 | (sizeof(sch->sense_data) << 8);
+        }
+    }
+    /* Store the irb to the guest. */
+    copy_irb_to_guest(target_irb, &irb);
+
+    /* Clear conditions on subchannel, if applicable. */
+    if (stctl & SCSW_STCTL_STATUS_PEND) {
+        s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
+        if ((stctl != (SCSW_STCTL_INTERMEDIATE | SCSW_STCTL_STATUS_PEND)) ||
+            ((fctl & SCSW_FCTL_HALT_FUNC) &&
+             (actl & SCSW_ACTL_SUSP))) {
+            s->ctrl &= ~SCSW_CTRL_MASK_FCTL;
+        }
+        if (stctl != (SCSW_STCTL_INTERMEDIATE | SCSW_STCTL_STATUS_PEND)) {
+            s->flags &= ~SCSW_FLAGS_MASK_PNO;
+            s->ctrl &= ~(SCSW_ACTL_RESUME_PEND |
+                         SCSW_ACTL_START_PEND |
+                         SCSW_ACTL_HALT_PEND |
+                         SCSW_ACTL_CLEAR_PEND |
+                         SCSW_ACTL_SUSP);
+        } else {
+            if ((actl & SCSW_ACTL_SUSP) &&
+                (fctl & SCSW_FCTL_START_FUNC)) {
+                s->flags &= ~SCSW_FLAGS_MASK_PNO;
+                if (fctl & SCSW_FCTL_HALT_FUNC) {
+                    s->ctrl &= ~(SCSW_ACTL_RESUME_PEND |
+                                 SCSW_ACTL_START_PEND |
+                                 SCSW_ACTL_HALT_PEND |
+                                 SCSW_ACTL_CLEAR_PEND |
+                                 SCSW_ACTL_SUSP);
+                } else {
+                    s->ctrl &= ~SCSW_ACTL_RESUME_PEND;
+                }
+            }
+        }
+        /* Clear pending sense data. */
+        if (p->chars & PMCW_CHARS_MASK_CSENSE) {
+            memset(sch->sense_data, 0 , sizeof(sch->sense_data));
+        }
+    }
+
+    ret = ((stctl & SCSW_STCTL_STATUS_PEND) == 0);
+
+out:
+    return ret;
+}
+
+static void copy_crw_to_guest(CRW *dest, const CRW *src)
+{
+    dest->flags = cpu_to_be16(src->flags);
+    dest->rsid = cpu_to_be16(src->rsid);
+}
+
+int css_do_stcrw(CRW *crw)
+{
+    CrwContainer *crw_cont;
+    int ret;
+
+    crw_cont = QTAILQ_FIRST(&channel_subsys->pending_crws);
+    if (crw_cont) {
+        QTAILQ_REMOVE(&channel_subsys->pending_crws, crw_cont, sibling);
+        copy_crw_to_guest(crw, &crw_cont->crw);
+        g_free(crw_cont);
+        ret = 0;
+    } else {
+        /* List was empty, turn crw machine checks on again. */
+        memset(crw, 0, sizeof(*crw));
+        channel_subsys->do_crw_mchk = true;
+        ret = 1;
+    }
+
+    return ret;
+}
+
+int css_do_tpi(uint64_t addr, int lowcore)
+{
+    /* No pending interrupts for !KVM. */
+    return 0;
+ }
+
+int css_collect_chp_desc(int m, uint8_t cssid, uint8_t f_chpid, uint8_t l_chpid,
+                         int rfmt, void *buf)
+{
+    int i, desc_size;
+    uint32_t words[8];
+    uint32_t chpid_type_word;
+    CssImage *css;
+
+    if (!m && !cssid) {
+        css = channel_subsys->css[channel_subsys->default_cssid];
+    } else {
+        css = channel_subsys->css[cssid];
+    }
+    if (!css) {
+        return 0;
+    }
+    desc_size = 0;
+    for (i = f_chpid; i <= l_chpid; i++) {
+        if (css->chpids[i].in_use) {
+            chpid_type_word = 0x80000000 | (css->chpids[i].type << 8) | i;
+            if (rfmt == 0) {
+                words[0] = cpu_to_be32(chpid_type_word);
+                words[1] = 0;
+                memcpy(buf + desc_size, words, 8);
+                desc_size += 8;
+            } else if (rfmt == 1) {
+                words[0] = cpu_to_be32(chpid_type_word);
+                words[1] = 0;
+                words[2] = 0;
+                words[3] = 0;
+                words[4] = 0;
+                words[5] = 0;
+                words[6] = 0;
+                words[7] = 0;
+                memcpy(buf + desc_size, words, 32);
+                desc_size += 32;
+            }
+        }
+    }
+    return desc_size;
+}
+
+void css_do_schm(uint8_t mbk, int update, int dct, uint64_t mbo)
+{
+    /* dct is currently ignored (not really meaningful for our devices) */
+    /* TODO: Don't ignore mbk. */
+    if (update && !channel_subsys->chnmon_active) {
+        /* Enable measuring. */
+        channel_subsys->chnmon_area = mbo;
+        channel_subsys->chnmon_active = true;
+    }
+    if (!update && channel_subsys->chnmon_active) {
+        /* Disable measuring. */
+        channel_subsys->chnmon_area = 0;
+        channel_subsys->chnmon_active = false;
+    }
+}
+
+int css_do_rsch(SubchDev *sch)
+{
+    SCSW *s = &sch->curr_status.scsw;
+    PMCW *p = &sch->curr_status.pmcw;
+    int ret;
+
+    if (!(p->flags & (PMCW_FLAGS_MASK_DNV | PMCW_FLAGS_MASK_ENA))) {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    if (s->ctrl & SCSW_STCTL_STATUS_PEND) {
+        ret = -EINPROGRESS;
+        goto out;
+    }
+
+    if (((s->ctrl & SCSW_CTRL_MASK_FCTL) != SCSW_FCTL_START_FUNC) ||
+        (s->ctrl & SCSW_ACTL_RESUME_PEND) ||
+        (!(s->ctrl & SCSW_ACTL_SUSP))) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    /* If monitoring is active, update counter. */
+    if (channel_subsys->chnmon_active) {
+        css_update_chnmon(sch);
+    }
+
+    s->ctrl |= SCSW_ACTL_RESUME_PEND;
+    do_subchannel_work(sch);
+    ret = 0;
+
+out:
+    return ret;
+}
+
+int css_do_rchp(uint8_t cssid, uint8_t chpid)
+{
+    uint8_t real_cssid;
+
+    if (cssid > channel_subsys->max_cssid) {
+        return -EINVAL;
+    }
+    if (channel_subsys->max_cssid == 0) {
+        real_cssid = channel_subsys->default_cssid;
+    } else {
+        real_cssid = cssid;
+    }
+    if (!channel_subsys->css[real_cssid]) {
+        return -EINVAL;
+    }
+
+    if (!channel_subsys->css[real_cssid]->chpids[chpid].in_use) {
+        return -ENODEV;
+    }
+
+    if (!channel_subsys->css[real_cssid]->chpids[chpid].is_virtual) {
+        fprintf(stderr,
+                "rchp unsupported for non-virtual chpid %x.%02x!\n",
+                real_cssid, chpid);
+        return -ENODEV;
+    }
+
+    /* We don't really use a channel path, so we're done here. */
+    css_queue_crw(CRW_RSC_CHP, CRW_ERC_INIT,
+                  channel_subsys->max_cssid > 0 ? 1 : 0, chpid);
+    if (channel_subsys->max_cssid > 0) {
+        css_queue_crw(CRW_RSC_CHP, CRW_ERC_INIT, 0, real_cssid << 8);
+    }
+    return 0;
+}
+
+bool css_schid_final(uint8_t cssid, uint8_t ssid, uint16_t schid)
+{
+    SubchSet *set;
+
+    if (cssid > MAX_CSSID || ssid > MAX_SSID || !channel_subsys->css[cssid] ||
+        !channel_subsys->css[cssid]->sch_set[ssid]) {
+        return true;
+    }
+    set = channel_subsys->css[cssid]->sch_set[ssid];
+    return schid > find_last_bit(set->schids_used,
+                                 (MAX_SCHID + 1) / sizeof(unsigned long));
+}
+
+static int css_add_virtual_chpid(uint8_t cssid, uint8_t chpid, uint8_t type)
+{
+    CssImage *css;
+
+    trace_css_chpid_add(cssid, chpid, type);
+    if (cssid > MAX_CSSID) {
+        return -EINVAL;
+    }
+    css = channel_subsys->css[cssid];
+    if (!css) {
+        return -EINVAL;
+    }
+    if (css->chpids[chpid].in_use) {
+        return -EEXIST;
+    }
+    css->chpids[chpid].in_use = 1;
+    css->chpids[chpid].type = type;
+    css->chpids[chpid].is_virtual = 1;
+
+    css_generate_chp_crws(cssid, chpid);
+
+    return 0;
+}
+
+void css_sch_build_virtual_schib(SubchDev *sch, uint8_t chpid, uint8_t type)
+{
+    PMCW *p = &sch->curr_status.pmcw;
+    SCSW *s = &sch->curr_status.scsw;
+    int i;
+    CssImage *css = channel_subsys->css[sch->cssid];
+
+    assert(css != NULL);
+    memset(p, 0, sizeof(PMCW));
+    p->flags |= PMCW_FLAGS_MASK_DNV;
+    p->devno = sch->devno;
+    /* single path */
+    p->pim = 0x80;
+    p->pom = 0xff;
+    p->pam = 0x80;
+    p->chpid[0] = chpid;
+    if (!css->chpids[chpid].in_use) {
+        css_add_virtual_chpid(sch->cssid, chpid, type);
+    }
+
+    memset(s, 0, sizeof(SCSW));
+    sch->curr_status.mba = 0;
+    for (i = 0; i < ARRAY_SIZE(sch->curr_status.mda); i++) {
+        sch->curr_status.mda[i] = 0;
+    }
+}
+
+SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t ssid, uint16_t schid)
+{
+    uint8_t real_cssid;
+
+    real_cssid = (!m && (cssid == 0)) ? channel_subsys->default_cssid : cssid;
+
+    if (!channel_subsys->css[real_cssid]) {
+        return NULL;
+    }
+
+    if (!channel_subsys->css[real_cssid]->sch_set[ssid]) {
+        return NULL;
+    }
+
+    return channel_subsys->css[real_cssid]->sch_set[ssid]->sch[schid];
+}
+
+bool css_subch_visible(SubchDev *sch)
+{
+    if (sch->ssid > channel_subsys->max_ssid) {
+        return false;
+    }
+
+    if (sch->cssid != channel_subsys->default_cssid) {
+        return (channel_subsys->max_cssid > 0);
+    }
+
+    return true;
+}
+
+bool css_present(uint8_t cssid)
+{
+    return (channel_subsys->css[cssid] != NULL);
+}
+
+bool css_devno_used(uint8_t cssid, uint8_t ssid, uint16_t devno)
+{
+    if (!channel_subsys->css[cssid]) {
+        return false;
+    }
+    if (!channel_subsys->css[cssid]->sch_set[ssid]) {
+        return false;
+    }
+
+    return !!test_bit(devno,
+                      channel_subsys->css[cssid]->sch_set[ssid]->devnos_used);
+}
+
+void css_subch_assign(uint8_t cssid, uint8_t ssid, uint16_t schid,
+                      uint16_t devno, SubchDev *sch)
+{
+    CssImage *css;
+    SubchSet *s_set;
+
+    trace_css_assign_subch(sch ? "assign" : "deassign", cssid, ssid, schid,
+                           devno);
+    if (!channel_subsys->css[cssid]) {
+        fprintf(stderr,
+                "Suspicious call to %s (%x.%x.%04x) for non-existing css!\n",
+                __func__, cssid, ssid, schid);
+        return;
+    }
+    css = channel_subsys->css[cssid];
+
+    if (!css->sch_set[ssid]) {
+        css->sch_set[ssid] = g_malloc0(sizeof(SubchSet));
+    }
+    s_set = css->sch_set[ssid];
+
+    s_set->sch[schid] = sch;
+    if (sch) {
+        set_bit(schid, s_set->schids_used);
+        set_bit(devno, s_set->devnos_used);
+    } else {
+        clear_bit(schid, s_set->schids_used);
+        clear_bit(devno, s_set->devnos_used);
+    }
+}
+
+void css_queue_crw(uint8_t rsc, uint8_t erc, int chain, uint16_t rsid)
+{
+    CrwContainer *crw_cont;
+
+    trace_css_crw(rsc, erc, rsid, chain ? "(chained)" : "");
+    /* TODO: Maybe use a static crw pool? */
+    crw_cont = g_try_malloc0(sizeof(CrwContainer));
+    if (!crw_cont) {
+        channel_subsys->crws_lost = true;
+        return;
+    }
+    crw_cont->crw.flags = (rsc << 8) | erc;
+    if (chain) {
+        crw_cont->crw.flags |= CRW_FLAGS_MASK_C;
+    }
+    crw_cont->crw.rsid = rsid;
+    if (channel_subsys->crws_lost) {
+        crw_cont->crw.flags |= CRW_FLAGS_MASK_R;
+        channel_subsys->crws_lost = false;
+    }
+
+    QTAILQ_INSERT_TAIL(&channel_subsys->pending_crws, crw_cont, sibling);
+
+    if (channel_subsys->do_crw_mchk) {
+        S390CPU *cpu = s390_cpu_addr2state(0);
+
+        channel_subsys->do_crw_mchk = false;
+        /* Inject crw pending machine check. */
+        s390_crw_mchk(cpu);
+    }
+}
+
+void css_generate_sch_crws(uint8_t cssid, uint8_t ssid, uint16_t schid,
+                           int hotplugged, int add)
+{
+    uint8_t guest_cssid;
+    bool chain_crw;
+
+    if (add && !hotplugged) {
+        return;
+    }
+    if (channel_subsys->max_cssid == 0) {
+        /* Default cssid shows up as 0. */
+        guest_cssid = (cssid == channel_subsys->default_cssid) ? 0 : cssid;
+    } else {
+        /* Show real cssid to the guest. */
+        guest_cssid = cssid;
+    }
+    /*
+     * Only notify for higher subchannel sets/channel subsystems if the
+     * guest has enabled it.
+     */
+    if ((ssid > channel_subsys->max_ssid) ||
+        (guest_cssid > channel_subsys->max_cssid) ||
+        ((channel_subsys->max_cssid == 0) &&
+         (cssid != channel_subsys->default_cssid))) {
+        return;
+    }
+    chain_crw = (channel_subsys->max_ssid > 0) ||
+            (channel_subsys->max_cssid > 0);
+    css_queue_crw(CRW_RSC_SUBCH, CRW_ERC_IPI, chain_crw ? 1 : 0, schid);
+    if (chain_crw) {
+        css_queue_crw(CRW_RSC_SUBCH, CRW_ERC_IPI, 0,
+                      (guest_cssid << 8) | (ssid << 4));
+    }
+}
+
+void css_generate_chp_crws(uint8_t cssid, uint8_t chpid)
+{
+    /* TODO */
+}
+
+int css_enable_mcsse(void)
+{
+    trace_css_enable_facility("mcsse");
+    channel_subsys->max_cssid = MAX_CSSID;
+    return 0;
+}
+
+int css_enable_mss(void)
+{
+    trace_css_enable_facility("mss");
+    channel_subsys->max_ssid = MAX_SSID;
+    return 0;
+}
+
+static void css_init(void)
+{
+    channel_subsys = g_malloc0(sizeof(*channel_subsys));
+    QTAILQ_INIT(&channel_subsys->pending_crws);
+    channel_subsys->do_crw_mchk = true;
+    channel_subsys->crws_lost = false;
+    channel_subsys->chnmon_active = false;
+}
+machine_init(css_init);
+
+void css_reset_sch(SubchDev *sch)
+{
+    PMCW *p = &sch->curr_status.pmcw;
+
+    p->intparm = 0;
+    p->flags &= ~(PMCW_FLAGS_MASK_ISC | PMCW_FLAGS_MASK_ENA |
+                  PMCW_FLAGS_MASK_LM | PMCW_FLAGS_MASK_MME |
+                  PMCW_FLAGS_MASK_MP | PMCW_FLAGS_MASK_TF);
+    p->flags |= PMCW_FLAGS_MASK_DNV;
+    p->devno = sch->devno;
+    p->pim = 0x80;
+    p->lpm = p->pim;
+    p->pnom = 0;
+    p->lpum = 0;
+    p->mbi = 0;
+    p->pom = 0xff;
+    p->pam = 0x80;
+    p->chars &= ~(PMCW_CHARS_MASK_MBFC | PMCW_CHARS_MASK_XMWME |
+                  PMCW_CHARS_MASK_CSENSE);
+
+    memset(&sch->curr_status.scsw, 0, sizeof(sch->curr_status.scsw));
+    sch->curr_status.mba = 0;
+
+    sch->channel_prog = 0x0;
+    sch->last_cmd_valid = false;
+    sch->orb = NULL;
+}
+
+void css_reset(void)
+{
+    CrwContainer *crw_cont;
+
+    /* Clean up monitoring. */
+    channel_subsys->chnmon_active = false;
+    channel_subsys->chnmon_area = 0;
+
+    /* Clear pending CRWs. */
+    while ((crw_cont = QTAILQ_FIRST(&channel_subsys->pending_crws))) {
+        QTAILQ_REMOVE(&channel_subsys->pending_crws, crw_cont, sibling);
+        g_free(crw_cont);
+    }
+    channel_subsys->do_crw_mchk = true;
+    channel_subsys->crws_lost = false;
+
+    /* Reset maximum ids. */
+    channel_subsys->max_cssid = 0;
+    channel_subsys->max_ssid = 0;
+}
diff --git a/hw/s390x/css.h b/hw/s390x/css.h
new file mode 100644
index 0000000..85ed05d
--- /dev/null
+++ b/hw/s390x/css.h
@@ -0,0 +1,99 @@ 
+/*
+ * Channel subsystem structures and definitions.
+ *
+ * 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 CSS_H
+#define CSS_H
+
+#include "ioinst.h"
+
+/* Channel subsystem constants. */
+#define MAX_SCHID 65535
+#define MAX_SSID 3
+#define MAX_CSSID 254 /* 255 is reserved */
+#define MAX_CHPID 255
+
+#define MAX_CIWS 62
+
+typedef struct CIW {
+    uint8_t type;
+    uint8_t command;
+    uint16_t count;
+} QEMU_PACKED CIW;
+
+typedef struct SenseId {
+    /* common part */
+    uint8_t reserved;        /* always 0x'FF' */
+    uint16_t cu_type;        /* control unit type */
+    uint8_t cu_model;        /* control unit model */
+    uint16_t dev_type;       /* device type */
+    uint8_t dev_model;       /* device model */
+    uint8_t unused;          /* padding byte */
+    /* extended part */
+    CIW ciw[MAX_CIWS];       /* variable # of CIWs */
+} QEMU_PACKED SenseId;
+
+/* Channel measurements, from linux/drivers/s390/cio/cmf.c. */
+typedef struct CMB {
+    uint16_t ssch_rsch_count;
+    uint16_t sample_count;
+    uint32_t device_connect_time;
+    uint32_t function_pending_time;
+    uint32_t device_disconnect_time;
+    uint32_t control_unit_queuing_time;
+    uint32_t device_active_only_time;
+    uint32_t reserved[2];
+} QEMU_PACKED CMB;
+
+typedef struct CMBE {
+    uint32_t ssch_rsch_count;
+    uint32_t sample_count;
+    uint32_t device_connect_time;
+    uint32_t function_pending_time;
+    uint32_t device_disconnect_time;
+    uint32_t control_unit_queuing_time;
+    uint32_t device_active_only_time;
+    uint32_t device_busy_time;
+    uint32_t initial_command_response_time;
+    uint32_t reserved[7];
+} QEMU_PACKED CMBE;
+
+struct SubchDev {
+    /* channel-subsystem related things: */
+    uint8_t cssid;
+    uint8_t ssid;
+    uint16_t schid;
+    uint16_t devno;
+    SCHIB curr_status;
+    uint8_t sense_data[32];
+    hwaddr channel_prog;
+    CCW1 last_cmd;
+    bool last_cmd_valid;
+    ORB *orb;
+    /* transport-provided data: */
+    int (*ccw_cb) (SubchDev *, CCW1);
+    SenseId id;
+    void *driver_data;
+};
+
+typedef SubchDev *(*css_subch_cb_func)(uint8_t m, uint8_t cssid, uint8_t ssid,
+                                       uint16_t schid);
+int css_create_css_image(uint8_t cssid, bool default_image);
+bool css_devno_used(uint8_t cssid, uint8_t ssid, uint16_t devno);
+void css_subch_assign(uint8_t cssid, uint8_t ssid, uint16_t schid,
+                      uint16_t devno, SubchDev *sch);
+void css_sch_build_virtual_schib(SubchDev *sch, uint8_t chpid, uint8_t type);
+void css_reset(void);
+void css_reset_sch(SubchDev *sch);
+void css_queue_crw(uint8_t rsc, uint8_t erc, int chain, uint16_t rsid);
+void css_generate_sch_crws(uint8_t cssid, uint8_t ssid, uint16_t schid,
+                           int hotplugged, int add);
+void css_generate_chp_crws(uint8_t cssid, uint8_t chpid);
+#endif
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 76a822c..778065c 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -399,6 +399,30 @@  void cpu_unlock(void);
 
 typedef struct SubchDev SubchDev;
 
+#ifndef CONFIG_USER_ONLY
+SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t ssid,
+                         uint16_t schid);
+bool css_subch_visible(SubchDev *sch);
+void css_conditional_io_interrupt(SubchDev *sch);
+int css_do_stsch(SubchDev *sch, SCHIB *schib);
+bool css_schid_final(uint8_t cssid, uint8_t ssid, uint16_t schid);
+int css_do_msch(SubchDev *sch, SCHIB *schib);
+int css_do_xsch(SubchDev *sch);
+int css_do_csch(SubchDev *sch);
+int css_do_hsch(SubchDev *sch);
+int css_do_ssch(SubchDev *sch, ORB *orb);
+int css_do_tsch(SubchDev *sch, IRB *irb);
+int css_do_stcrw(CRW *crw);
+int css_do_tpi(uint64_t addr, int lowcore);
+int css_collect_chp_desc(int m, uint8_t cssid, uint8_t f_chpid, uint8_t l_chpid,
+                         int rfmt, void *buf);
+void css_do_schm(uint8_t mbk, int update, int dct, uint64_t mbo);
+int css_enable_mcsse(void);
+int css_enable_mss(void);
+int css_do_rsch(SubchDev *sch);
+int css_do_rchp(uint8_t cssid, uint8_t chpid);
+bool css_present(uint8_t cssid);
+#else
 static inline SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t ssid,
                                        uint16_t schid)
 {
@@ -479,6 +503,7 @@  static inline bool css_present(uint8_t cssid)
 {
     return false;
 }
+#endif
 
 static inline void cpu_set_tls(CPUS390XState *env, target_ulong newtls)
 {
@@ -1031,4 +1056,41 @@  void program_interrupt(CPUS390XState *env, uint32_t code, int ilen);
 void QEMU_NORETURN runtime_exception(CPUS390XState *env, int excp,
                                      uintptr_t retaddr);
 
+#include <sysemu/kvm.h>
+
+static inline void kvm_s390_io_interrupt(S390CPU *cpu,
+                                        uint16_t subchannel_id,
+                                        uint16_t subchannel_nr,
+                                        uint32_t io_int_parm,
+                                        uint32_t io_int_word)
+{
+}
+static inline void kvm_s390_crw_mchk(S390CPU *cpu)
+{
+}
+
+static inline void s390_io_interrupt(S390CPU *cpu,
+                                     uint16_t subchannel_id,
+                                     uint16_t subchannel_nr,
+                                     uint32_t io_int_parm,
+                                     uint32_t io_int_word)
+{
+    if (kvm_enabled()) {
+        kvm_s390_io_interrupt(cpu, subchannel_id, subchannel_nr, io_int_parm,
+                              io_int_word);
+    } else {
+        cpu_inject_io(&cpu->env, subchannel_id, subchannel_nr, io_int_parm,
+                      io_int_word);
+    }
+}
+
+static inline void s390_crw_mchk(S390CPU *cpu)
+{
+    if (kvm_enabled()) {
+        kvm_s390_crw_mchk(cpu);
+    } else {
+        cpu_inject_crw_mchk(&cpu->env);
+    }
+}
+
 #endif
diff --git a/trace-events b/trace-events
index 1b54542..bbed1cd 100644
--- a/trace-events
+++ b/trace-events
@@ -1066,3 +1066,11 @@  ioinst(const char *insn) "IOINST: %s"
 ioinst_sch_id(const char *insn, int cssid, int ssid, int schid) "IOINST: %s (%x.%x.%04x)"
 ioinst_chp_id(const char *insn, int cssid, int chpid) "IOINST: %s (%x.%02x)"
 ioinst_chsc_cmd(uint16_t cmd, uint16_t len) "IOINST: chsc command %04x, len %04x"
+
+# hw/s390x/css.c
+css_enable_facility(const char *facility) "CSS: enable %s"
+css_crw(uint8_t rsc, uint8_t erc, uint16_t rsid, const char *chained) "CSS: queueing crw: rsc=%x, erc=%x, rsid=%x %s"
+css_chpid_add(uint8_t cssid, uint8_t chpid, uint8_t type) "CSS: add chpid %x.%02x (type %02x)"
+css_new_image(uint8_t cssid, const char *default_cssid) "CSS: add css image %02x %s"
+css_assign_subch(const char *do_assign, uint8_t cssid, uint8_t ssid, uint16_t schid, uint16_t devno) "CSS: %s %x.%x.%04x (devno %04x)"
+css_io_interrupt(int cssid, int ssid, int schid, uint32_t intparm, uint8_t isc, const char *conditional) "CSS: I/O interrupt on sch %x.%x.%04x (intparm %08x, isc %x) %s"