diff --git a/hw/misc/Makefile.objs b/hw/misc/Makefile.objs
index af2b503824e..6d50b03cfdb 100644
--- a/hw/misc/Makefile.objs
+++ b/hw/misc/Makefile.objs
@@ -64,6 +64,7 @@ obj-$(CONFIG_MPS2_FPGAIO) += mps2-fpgaio.o
 obj-$(CONFIG_MPS2_SCC) += mps2-scc.o
 
 obj-$(CONFIG_TZ_MPC) += tz-mpc.o
+obj-$(CONFIG_TZ_MSC) += tz-msc.o
 obj-$(CONFIG_TZ_PPC) += tz-ppc.o
 obj-$(CONFIG_IOTKIT_SECCTL) += iotkit-secctl.o
 obj-$(CONFIG_IOTKIT_SYSCTL) += iotkit-sysctl.o
diff --git a/include/hw/misc/tz-msc.h b/include/hw/misc/tz-msc.h
new file mode 100644
index 00000000000..116b96ae9b8
--- /dev/null
+++ b/include/hw/misc/tz-msc.h
@@ -0,0 +1,79 @@
+/*
+ * ARM TrustZone master security controller emulation
+ *
+ * Copyright (c) 2018 Linaro Limited
+ * Written by Peter Maydell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 or
+ * (at your option) any later version.
+ */
+
+/*
+ * This is a model of the TrustZone master security controller (MSC).
+ * It is documented in the ARM CoreLink SIE-200 System IP for Embedded TRM
+ * (DDI 0571G):
+ * https://developer.arm.com/products/architecture/m-profile/docs/ddi0571/g
+ *
+ * The MSC sits in front of a device which can be a bus master (such as
+ * a DMA controller) and allows secure software to configure it to either
+ * pass through or reject transactions made by that bus master.
+ * Rejected transactions may be configured to either be aborted, or to
+ * behave as RAZ/WI. An interrupt can be signalled for a rejected transaction.
+ *
+ * The MSC has no register interface -- it is configured purely by a
+ * collection of input signals from other hardware in the system. Typically
+ * they are either hardwired or exposed in an ad-hoc register interface by
+ * the SoC that uses the MSC.
+ *
+ * We don't currently implement the irq_enable GPIO input, because on
+ * the MPS2 FPGA images it is always tied high, which is awkward to
+ * implement in QEMU.
+ *
+ * QEMU interface:
+ * + Named GPIO input "cfg_nonsec": set to 1 if the bus master should be
+ *   treated as nonsecure, or 0 for secure
+ * + Named GPIO input "cfg_sec_resp": set to 1 if a rejected transaction should
+ *   result in a transaction error, or 0 for the transaction to RAZ/WI
+ * + Named GPIO input "irq_clear": set to 1 to clear a pending interrupt
+ * + Named GPIO output "irq": set for a transaction-failed interrupt
+ * + Property "downstream": MemoryRegion defining where bus master transactions
+ *   are made if they are not blocked
+ * + Property "idau": an object implementing IDAUInterface, which defines which
+ *   addresses should be treated as secure and which as non-secure.
+ *   This need not be the same IDAU as the one used by the CPU.
+ * + sysbus MMIO region 0: MemoryRegion defining the upstream end of the MSC;
+ *   this should be passed to the bus master device as the region it should
+ *   make memory transactions to
+ */
+
+#ifndef TZ_MSC_H
+#define TZ_MSC_H
+
+#include "hw/sysbus.h"
+#include "target/arm/idau.h"
+
+#define TYPE_TZ_MSC "tz-msc"
+#define TZ_MSC(obj) OBJECT_CHECK(TZMSC, (obj), TYPE_TZ_MSC)
+
+typedef struct TZMSC {
+    /*< private >*/
+    SysBusDevice parent_obj;
+
+    /*< public >*/
+
+    /* State: these just track the values of our input signals */
+    bool cfg_nonsec;
+    bool cfg_sec_resp;
+    bool irq_clear;
+    /* State: are we asserting irq ? */
+    bool irq_status;
+
+    qemu_irq irq;
+    MemoryRegion *downstream;
+    AddressSpace downstream_as;
+    MemoryRegion upstream;
+    IDAUInterface *idau;
+} TZMSC;
+
+#endif
diff --git a/hw/misc/tz-msc.c b/hw/misc/tz-msc.c
new file mode 100644
index 00000000000..9e352044ea5
--- /dev/null
+++ b/hw/misc/tz-msc.c
@@ -0,0 +1,308 @@
+/*
+ * ARM TrustZone master security controller emulation
+ *
+ * Copyright (c) 2018 Linaro Limited
+ * Written by Peter Maydell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 or
+ * (at your option) any later version.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qapi/error.h"
+#include "trace.h"
+#include "hw/sysbus.h"
+#include "hw/registerfields.h"
+#include "hw/misc/tz-msc.h"
+
+static void tz_msc_update_irq(TZMSC *s)
+{
+    bool level = s->irq_status;
+
+    trace_tz_msc_update_irq(level);
+    qemu_set_irq(s->irq, level);
+}
+
+static void tz_msc_cfg_nonsec(void *opaque, int n, int level)
+{
+    TZMSC *s = TZ_MSC(opaque);
+
+    trace_tz_msc_cfg_nonsec(level);
+    s->cfg_nonsec = level;
+}
+
+static void tz_msc_cfg_sec_resp(void *opaque, int n, int level)
+{
+    TZMSC *s = TZ_MSC(opaque);
+
+    trace_tz_msc_cfg_sec_resp(level);
+    s->cfg_sec_resp = level;
+}
+
+static void tz_msc_irq_clear(void *opaque, int n, int level)
+{
+    TZMSC *s = TZ_MSC(opaque);
+
+    trace_tz_msc_irq_clear(level);
+
+    s->irq_clear = level;
+    if (level) {
+        s->irq_status = false;
+        tz_msc_update_irq(s);
+    }
+}
+
+/* The MSC may either block a transaction by aborting it, block a
+ * transaction by making it RAZ/WI, allow it through with
+ * MemTxAttrs indicating a secure transaction, or allow it with
+ * MemTxAttrs indicating a non-secure transaction.
+ */
+typedef enum MSCAction {
+    MSCBlockAbort,
+    MSCBlockRAZWI,
+    MSCAllowSecure,
+    MSCAllowNonSecure,
+} MSCAction;
+
+static MSCAction tz_msc_check(TZMSC *s, hwaddr addr)
+{
+    /*
+     * Check whether to allow an access from the bus master, returning
+     * an MSCAction indicating the required behaviour. If the transaction
+     * is blocked, the caller must check cfg_sec_resp to determine
+     * whether to abort or RAZ/WI the transaction.
+     */
+    IDAUInterfaceClass *iic = IDAU_INTERFACE_GET_CLASS(s->idau);
+    IDAUInterface *ii = IDAU_INTERFACE(s->idau);
+    bool idau_exempt = false, idau_ns = true, idau_nsc = true;
+    int idau_region = IREGION_NOTVALID;
+
+    iic->check(ii, addr, &idau_region, &idau_exempt, &idau_ns, &idau_nsc);
+
+    if (idau_exempt) {
+        /*
+         * Uncheck region -- OK, transaction type depends on
+         * whether bus master is configured as Secure or NonSecure
+         */
+        return s->cfg_nonsec ? MSCAllowNonSecure : MSCAllowSecure;
+    }
+
+    if (idau_ns) {
+        /* NonSecure region -- always forward as NS transaction */
+        return MSCAllowNonSecure;
+    }
+
+    if (!s->cfg_nonsec) {
+        /* Access to Secure region by Secure bus master: OK */
+        return MSCAllowSecure;
+    }
+
+    /* Attempted access to Secure region by NS bus master: block */
+    trace_tz_msc_access_blocked(addr);
+    if (!s->cfg_sec_resp) {
+        return MSCBlockRAZWI;
+    }
+
+    /*
+     * The TRM isn't clear on behaviour if irq_clear is high when a
+     * transaction is blocked. We assume that the MSC behaves like the
+     * PPC, where holding irq_clear high suppresses the interrupt.
+     */
+    if (!s->irq_clear) {
+        s->irq_status = true;
+        tz_msc_update_irq(s);
+    }
+    return MSCBlockAbort;
+}
+
+static MemTxResult tz_msc_read(void *opaque, hwaddr addr, uint64_t *pdata,
+                               unsigned size, MemTxAttrs attrs)
+{
+    TZMSC *s = opaque;
+    AddressSpace *as = &s->downstream_as;
+    uint64_t data;
+    MemTxResult res;
+
+    switch (tz_msc_check(s, addr)) {
+    case MSCBlockAbort:
+        return MEMTX_ERROR;
+    case MSCBlockRAZWI:
+        *pdata = 0;
+        return MEMTX_OK;
+    case MSCAllowSecure:
+        attrs.secure = 1;
+        attrs.unspecified = 0;
+        break;
+    case MSCAllowNonSecure:
+        attrs.secure = 0;
+        attrs.unspecified = 0;
+        break;
+    }
+
+    switch (size) {
+    case 1:
+        data = address_space_ldub(as, addr, attrs, &res);
+        break;
+    case 2:
+        data = address_space_lduw_le(as, addr, attrs, &res);
+        break;
+    case 4:
+        data = address_space_ldl_le(as, addr, attrs, &res);
+        break;
+    case 8:
+        data = address_space_ldq_le(as, addr, attrs, &res);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    *pdata = data;
+    return res;
+}
+
+static MemTxResult tz_msc_write(void *opaque, hwaddr addr, uint64_t val,
+                                unsigned size, MemTxAttrs attrs)
+{
+    TZMSC *s = opaque;
+    AddressSpace *as = &s->downstream_as;
+    MemTxResult res;
+
+    switch (tz_msc_check(s, addr)) {
+    case MSCBlockAbort:
+        return MEMTX_ERROR;
+    case MSCBlockRAZWI:
+        return MEMTX_OK;
+    case MSCAllowSecure:
+        attrs.secure = 1;
+        attrs.unspecified = 0;
+        break;
+    case MSCAllowNonSecure:
+        attrs.secure = 0;
+        attrs.unspecified = 0;
+        break;
+    }
+
+    switch (size) {
+    case 1:
+        address_space_stb(as, addr, val, attrs, &res);
+        break;
+    case 2:
+        address_space_stw_le(as, addr, val, attrs, &res);
+        break;
+    case 4:
+        address_space_stl_le(as, addr, val, attrs, &res);
+        break;
+    case 8:
+        address_space_stq_le(as, addr, val, attrs, &res);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    return res;
+}
+
+static const MemoryRegionOps tz_msc_ops = {
+    .read_with_attrs = tz_msc_read,
+    .write_with_attrs = tz_msc_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
+static void tz_msc_reset(DeviceState *dev)
+{
+    TZMSC *s = TZ_MSC(dev);
+
+    trace_tz_msc_reset();
+    s->cfg_sec_resp = false;
+    s->cfg_nonsec = false;
+    s->irq_clear = 0;
+    s->irq_status = 0;
+}
+
+static void tz_msc_init(Object *obj)
+{
+    DeviceState *dev = DEVICE(obj);
+    TZMSC *s = TZ_MSC(obj);
+
+    qdev_init_gpio_in_named(dev, tz_msc_cfg_nonsec, "cfg_nonsec", 1);
+    qdev_init_gpio_in_named(dev, tz_msc_cfg_sec_resp, "cfg_sec_resp", 1);
+    qdev_init_gpio_in_named(dev, tz_msc_irq_clear, "irq_clear", 1);
+    qdev_init_gpio_out_named(dev, &s->irq, "irq", 1);
+}
+
+static void tz_msc_realize(DeviceState *dev, Error **errp)
+{
+    Object *obj = OBJECT(dev);
+    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
+    TZMSC *s = TZ_MSC(dev);
+    const char *name = "tz-msc-downstream";
+    uint64_t size;
+
+    /*
+     * We can't create the upstream end of the port until realize,
+     * as we don't know the size of the MR used as the downstream until then.
+     * We insist on having a downstream, to avoid complicating the
+     * code with handling the "don't know how big this is" case. It's easy
+     * enough for the user to create an unimplemented_device as downstream
+     * if they have nothing else to plug into this.
+     */
+    if (!s->downstream) {
+        error_setg(errp, "MSC 'downstream' link not set");
+        return;
+    }
+    if (!s->idau) {
+        error_setg(errp, "MSC 'idau' link not set");
+        return;
+    }
+
+    size = memory_region_size(s->downstream);
+    address_space_init(&s->downstream_as, s->downstream, name);
+    memory_region_init_io(&s->upstream, obj, &tz_msc_ops, s, name, size);
+    sysbus_init_mmio(sbd, &s->upstream);
+}
+
+static const VMStateDescription tz_msc_vmstate = {
+    .name = "tz-msc",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_BOOL(cfg_nonsec, TZMSC),
+        VMSTATE_BOOL(cfg_sec_resp, TZMSC),
+        VMSTATE_BOOL(irq_clear, TZMSC),
+        VMSTATE_BOOL(irq_status, TZMSC),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static Property tz_msc_properties[] = {
+    DEFINE_PROP_LINK("downstream", TZMSC, downstream,
+                     TYPE_MEMORY_REGION, MemoryRegion *),
+    DEFINE_PROP_LINK("idau", TZMSC, idau,
+                     TYPE_IDAU_INTERFACE, IDAUInterface *),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void tz_msc_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = tz_msc_realize;
+    dc->vmsd = &tz_msc_vmstate;
+    dc->reset = tz_msc_reset;
+    dc->props = tz_msc_properties;
+}
+
+static const TypeInfo tz_msc_info = {
+    .name = TYPE_TZ_MSC,
+    .parent = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(TZMSC),
+    .instance_init = tz_msc_init,
+    .class_init = tz_msc_class_init,
+};
+
+static void tz_msc_register_types(void)
+{
+    type_register_static(&tz_msc_info);
+}
+
+type_init(tz_msc_register_types);
diff --git a/MAINTAINERS b/MAINTAINERS
index cb780f463cb..b2f8b562dc5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -465,6 +465,8 @@ F: hw/misc/tz-ppc.c
 F: include/hw/misc/tz-ppc.h
 F: hw/misc/tz-mpc.c
 F: include/hw/misc/tz-mpc.h
+F: hw/misc/tz-msc.c
+F: include/hw/misc/tz-msc.h
 
 ARM cores
 M: Peter Maydell <peter.maydell@linaro.org>
diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
index ebbdcb29f38..0483d548d96 100644
--- a/default-configs/arm-softmmu.mak
+++ b/default-configs/arm-softmmu.mak
@@ -111,6 +111,7 @@ CONFIG_MPS2_FPGAIO=y
 CONFIG_MPS2_SCC=y
 
 CONFIG_TZ_MPC=y
+CONFIG_TZ_MSC=y
 CONFIG_TZ_PPC=y
 CONFIG_IOTKIT=y
 CONFIG_IOTKIT_SECCTL=y
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 7faf7592832..52466c77c4e 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -92,6 +92,15 @@ tz_mpc_mem_blocked_write(uint64_t addr, uint64_t data, unsigned size, bool secur
 tz_mpc_translate(uint64_t addr, int flags, const char *idx, const char *res) "TZ MPC translate: addr 0x%" PRIx64 " flags 0x%x iommu_idx %s: %s"
 tz_mpc_iommu_notify(uint64_t addr) "TZ MPC iommu: notifying UNMAP/MAP for 0x%" PRIx64
 
+# hw/misc/tz-msc.c
+tz_msc_reset(void) "TZ MSC: reset"
+tz_msc_cfg_nonsec(int level) "TZ MSC: cfg_nonsec = %d"
+tz_msc_cfg_sec_resp(int level) "TZ MSC: cfg_sec_resp = %d"
+tz_msc_irq_enable(int level) "TZ MSC: int_enable = %d"
+tz_msc_irq_clear(int level) "TZ MSC: int_clear = %d"
+tz_msc_update_irq(int level) "TZ MSC: setting irq line to %d"
+tz_msc_access_blocked(uint64_t offset) "TZ MSC: offset 0x%" PRIx64 " access blocked"
+
 # hw/misc/tz-ppc.c
 tz_ppc_reset(void) "TZ PPC: reset"
 tz_ppc_cfg_nonsec(int n, int level) "TZ PPC: cfg_nonsec[%d] = %d"
