diff --git a/hw/fsi/cfam.c b/hw/fsi/cfam.c
index 9a9e65d33f..414dcebe63 100644
--- a/hw/fsi/cfam.c
+++ b/hw/fsi/cfam.c
@@ -7,12 +7,13 @@
 
 #include "qemu/osdep.h"
 
+#include "qemu/bitops.h"
 #include "qapi/error.h"
 #include "qemu/log.h"
 #include "trace.h"
 
-#include "hw/fsi/bits.h"
 #include "hw/fsi/cfam.h"
+#include "hw/fsi/fsi.h"
 #include "hw/fsi/engine-scratchpad.h"
 
 #include "hw/qdev-properties.h"
diff --git a/hw/fsi/fsi-master.c b/hw/fsi/fsi-master.c
new file mode 100644
index 0000000000..fe1693539a
--- /dev/null
+++ b/hw/fsi/fsi-master.c
@@ -0,0 +1,203 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM Flexible Service Interface master
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+
+#include "qemu/log.h"
+
+#include "hw/fsi/bits.h"
+#include "hw/fsi/fsi-master.h"
+
+#define TYPE_OP_BUS "opb"
+
+#define TO_REG(x)                               ((x) >> 2)
+
+#define FSI_MMODE                               TO_REG(0x000)
+#define   FSI_MMODE_IPOLL_DMA_EN                BE_BIT(0)
+#define   FSI_MMODE_HW_ERROR_RECOVERY_EN        BE_BIT(1)
+#define   FSI_MMODE_RELATIVE_ADDRESS_EN         BE_BIT(2)
+#define   FSI_MMODE_PARITY_CHECK_EN             BE_BIT(3)
+#define   FSI_MMODE_CLOCK_DIVIDER_0             BE_GENMASK(4, 13)
+#define   FSI_MMODE_CLOCK_DIVIDER_1             BE_GENMASK(14, 23)
+#define   FSI_MMODE_DEBUG_EN                    BE_BIT(24)
+
+#define FSI_MDELAY                              TO_REG(0x004)
+#define   FSI_MDELAY_ECHO_0                     BE_GENMASK(0, 3)
+#define   FSI_MDELAY_SEND_0                     BE_GENMASK(4, 7)
+#define   FSI_MDELAY_ECHO_1                     BE_GENMASK(8, 11)
+#define   FSI_MDELAY_SEND_1                     BE_GENMASK(12, 15)
+
+#define FSI_MENP0                               TO_REG(0x010)
+#define FSI_MENP32                              TO_REG(0x014)
+#define FSI_MSENP0                              TO_REG(0x018)
+#define FSI_MLEVP0                              TO_REG(0x018)
+#define FSI_MSENP32                             TO_REG(0x01c)
+#define FSI_MLEVP32                             TO_REG(0x01c)
+#define FSI_MCENP0                              TO_REG(0x020)
+#define FSI_MREFP0                              TO_REG(0x020)
+#define FSI_MCENP32                             TO_REG(0x024)
+#define FSI_MREFP32                             TO_REG(0x024)
+
+#define FSI_MAEB                                TO_REG(0x070)
+#define   FSI_MAEB_ANY_CPU_ERROR                BE_BIT(0)
+#define   FSI_MAEB_ANY_DMA_ERROR                BE_GENMASK(1, 16)
+#define   FSI_MAEB_ANY_PARITY_ERROR             BE_BIT(17)
+
+#define FSI_MVER                                TO_REG(0x074)
+#define   FSI_MVER_VERSION                      BE_GENMASK(0, 7)
+#define   FSI_MVER_BRIDGES                      BE_GENMASK(8, 15)
+#define   FSI_MVER_PORTS                        BE_GENMASK(16, 23)
+
+#define FSI_MRESP0                              TO_REG(0x0d0)
+#define   FSI_MRESP0_RESET_PORT_GENERAL         BE_BIT(0)
+#define   FSI_MRESP0_RESET_PORT_ERROR           BE_BIT(1)
+#define   FSI_MRESP0_RESET_ALL_BRIDGES_GENERAL  BE_BIT(2)
+#define   FSI_MRESP0_RESET_ALL_PORTS_GENERAL    BE_BIT(3)
+#define   FSI_MRESP0_RESET_MASTER               BE_BIT(4)
+#define   FSI_MRESP0_RESET_PARITY_ERROR_LATCH   BE_BIT(5)
+
+#define FSI_MRESB0                              TO_REG(0x1d0)
+#define   FSI_MRESB0_RESET_GENERAL              BE_BIT(0)
+#define   FSI_MRESB0_RESET_ERROR                BE_BIT(1)
+#define   FSI_MRESB0_SET_DMA_SUSPEND            BE_BIT(5)
+#define   FSI_MRESB0_CLEAR_DMA_SUSPEND          BE_BIT(6)
+#define   FSI_MRESB0_SET_DELAY_MEASURE          BE_BIT(7)
+
+#define FSI_MECTRL                              TO_REG(0x2e0)
+#define   FSI_MECTRL_TEST_PULSE                 BE_GENMASK(0, 7)
+#define   FSI_MECTRL_INHIBIT_PARITY_ERROR       BE_GENMASK(8, 15)
+#define   FSI_MECTRL_ENABLE_OPB_ERR_ACK         BE_BIT(16)
+#define   FSI_MECTRL_AUTO_TERMINATE             BE_BIT(17)
+#define   FSI_MECTRL_PORT_ERROR_FREEZE          BE_BIT(18)
+
+static uint64_t fsi_master_read(void *opaque, hwaddr addr, unsigned size)
+{
+    FSIMasterState *s = FSI_MASTER(opaque);
+
+    qemu_log_mask(LOG_UNIMP, "%s: read @0x%" HWADDR_PRIx " size=%d\n",
+                  __func__, addr, size);
+
+    if (addr + size > sizeof(s->regs)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Out of bounds read: 0x%"HWADDR_PRIx" for %u\n",
+                      __func__, addr, size);
+        return 0;
+    }
+
+    return s->regs[TO_REG(addr)];
+}
+
+static void fsi_master_write(void *opaque, hwaddr addr, uint64_t data,
+                             unsigned size)
+{
+    FSIMasterState *s = FSI_MASTER(opaque);
+
+    qemu_log_mask(LOG_UNIMP, "%s: write @0x%" HWADDR_PRIx " size=%d "
+                  "value=%"PRIx64"\n", __func__, addr, size, data);
+
+    if (addr + size > sizeof(s->regs)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Out of bounds write: %"HWADDR_PRIx" for %u\n",
+                      __func__, addr, size);
+        return;
+    }
+
+    switch (TO_REG(addr)) {
+    case FSI_MENP0:
+        s->regs[FSI_MENP0] = data;
+        break;
+    case FSI_MENP32:
+        s->regs[FSI_MENP32] = data;
+        break;
+    case FSI_MSENP0:
+        s->regs[FSI_MENP0] |= data;
+        break;
+    case FSI_MSENP32:
+        s->regs[FSI_MENP32] |= data;
+        break;
+    case FSI_MCENP0:
+        s->regs[FSI_MENP0] &= ~data;
+        break;
+    case FSI_MCENP32:
+        s->regs[FSI_MENP32] &= ~data;
+        break;
+    case FSI_MRESP0:
+        /* Perform necessary resets leave register 0 to indicate no errors */
+        break;
+    case FSI_MRESB0:
+        if (data & FSI_MRESB0_RESET_GENERAL) {
+            device_cold_reset(DEVICE(opaque));
+        }
+        if (data & FSI_MRESB0_RESET_ERROR) {
+            /* FIXME: this seems dubious */
+            device_cold_reset(DEVICE(opaque));
+        }
+        break;
+    default:
+        s->regs[TO_REG(addr)] = data;
+    }
+}
+
+static const struct MemoryRegionOps fsi_master_ops = {
+    .read = fsi_master_read,
+    .write = fsi_master_write,
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static void fsi_master_realize(DeviceState *dev, Error **errp)
+{
+    FSIMasterState *s = FSI_MASTER(dev);
+    Error *err = NULL;
+
+    qbus_init(&s->bus, sizeof(s->bus), TYPE_FSI_BUS, DEVICE(s), NULL);
+
+    memory_region_init_io(&s->iomem, OBJECT(s), &fsi_master_ops, s,
+                          TYPE_FSI_MASTER, 0x10000000);
+    memory_region_init(&s->opb2fsi, OBJECT(s), "fsi.opb2fsi", 0x10000000);
+
+    object_property_set_bool(OBJECT(&s->bus), "realized", true, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
+    memory_region_add_subregion(&s->opb2fsi, 0, &s->bus.slave.mr);
+}
+
+static void fsi_master_reset(DeviceState *dev)
+{
+    FSIMasterState *s = FSI_MASTER(dev);
+
+    /* ASPEED default */
+    s->regs[FSI_MVER] = 0xe0050101;
+}
+
+static void fsi_master_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->bus_type = TYPE_OP_BUS;
+    dc->desc = "FSI Master";
+    dc->realize = fsi_master_realize;
+    dc->reset = fsi_master_reset;
+}
+
+static const TypeInfo fsi_master_info = {
+    .name = TYPE_FSI_MASTER,
+    .parent = TYPE_DEVICE,
+    .instance_size = sizeof(FSIMasterState),
+    .class_init = fsi_master_class_init,
+};
+
+static void fsi_register_types(void)
+{
+    type_register_static(&fsi_master_info);
+}
+
+type_init(fsi_register_types);
diff --git a/hw/fsi/fsi.c b/hw/fsi/fsi.c
new file mode 100644
index 0000000000..43f889fee9
--- /dev/null
+++ b/hw/fsi/fsi.c
@@ -0,0 +1,54 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM Flexible Service Interface
+ */
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+
+#include "hw/fsi/fsi.h"
+#include "hw/fsi/cfam.h"
+
+static void fsi_bus_realize(BusState *bus, Error **errp)
+{
+    FSIBus *s = FSI_BUS(bus);
+    Error *err = NULL;
+
+    /* FIXME: Should be realised elsewhere and added to the bus */
+    object_property_set_bool(OBJECT(&s->slave), "realized", true, &err);
+    if (err) {
+        error_propagate(errp, err);
+    }
+}
+
+static void fsi_bus_init(Object *o)
+{
+    FSIBus *s = FSI_BUS(o);
+
+    /* FIXME: Move this elsewhere */
+    object_initialize_child(o, TYPE_CFAM, &s->slave, TYPE_CFAM);
+    qdev_set_parent_bus(DEVICE(&s->slave), BUS(o), &error_abort);
+}
+
+static void fsi_bus_class_init(ObjectClass *klass, void *data)
+{
+    BusClass *bc = BUS_CLASS(klass);
+    bc->realize = fsi_bus_realize;
+}
+
+static const TypeInfo fsi_bus_info = {
+    .name = TYPE_FSI_BUS,
+    .parent = TYPE_BUS,
+    .instance_init = fsi_bus_init,
+    .instance_size = sizeof(FSIBus),
+    .class_init = fsi_bus_class_init,
+};
+
+static void fsi_bus_register_types(void)
+{
+    type_register_static(&fsi_bus_info);
+}
+
+type_init(fsi_bus_register_types);
diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
index 5600502b33..ca80d11cb9 100644
--- a/hw/fsi/meson.build
+++ b/hw/fsi/meson.build
@@ -1,4 +1,4 @@
 system_ss.add(when: 'CONFIG_LBUS', if_true: files('lbus.c'))
 system_ss.add(when: 'CONFIG_SCRATCHPAD', if_true: files('engine-scratchpad.c'))
 system_ss.add(when: 'CONFIG_CFAM', if_true: files('cfam.c'))
-system_ss.add(when: 'CONFIG_FSI', if_true: files('fsi-slave.c'))
+system_ss.add(when: 'CONFIG_FSI', if_true: files('fsi.c','fsi-master.c','fsi-slave.c'))
diff --git a/include/hw/fsi/cfam.h b/include/hw/fsi/cfam.h
index af9f88cb22..49877a7220 100644
--- a/include/hw/fsi/cfam.h
+++ b/include/hw/fsi/cfam.h
@@ -12,14 +12,14 @@
 #include "hw/fsi/fsi-slave.h"
 #include "hw/fsi/lbus.h"
 
-#define TYPE_FSI_BUS "fsi.bus"
-
 #define TYPE_CFAM "cfam"
 #define CFAM(obj) OBJECT_CHECK(CFAMState, (obj), TYPE_CFAM)
 
 #define CFAM_NR_REGS ((0x2e0 >> 2) + 1)
 
 #define TYPE_CFAM_CONFIG "cfam.config"
+OBJECT_DECLARE_SIMPLE_TYPE(CFAMConfig, CFAM_CONFIG)
+
 #define CFAM_CONFIG(obj) \
     OBJECT_CHECK(CFAMConfig, (obj), TYPE_CFAM_CONFIG)
 /* P9-ism */
@@ -35,8 +35,8 @@ typedef struct CFAMConfig {
 } CFAMConfig;
 
 #define TYPE_CFAM_PEEK "cfam.peek"
-#define CFAM_PEEK(obj) \
-    OBJECT_CHECK(CFAMPeek, (obj), TYPE_CFAM_PEEK)
+OBJECT_DECLARE_SIMPLE_TYPE(CFAMPeek, CFAM_PEEK)
+
 #define CFAM_PEEK_NR_REGS ((0x130 >> 2) + 1)
 
 typedef struct CFAMPeek {
diff --git a/include/hw/fsi/fsi-master.h b/include/hw/fsi/fsi-master.h
new file mode 100644
index 0000000000..847078919c
--- /dev/null
+++ b/include/hw/fsi/fsi-master.h
@@ -0,0 +1,30 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2019 IBM Corp.
+ *
+ * IBM Flexible Service Interface Master
+ */
+#ifndef FSI_FSI_MASTER_H
+#define FSI_FSI_MASTER_H
+
+#include "exec/memory.h"
+#include "hw/qdev-core.h"
+#include "hw/fsi/fsi.h"
+
+#define TYPE_FSI_MASTER "fsi.master"
+OBJECT_DECLARE_SIMPLE_TYPE(FSIMasterState, FSI_MASTER)
+
+#define FSI_MASTER_NR_REGS ((0x2e0 >> 2) + 1)
+
+typedef struct FSIMasterState {
+    DeviceState parent;
+    MemoryRegion iomem;
+    MemoryRegion opb2fsi;
+
+    FSIBus bus;
+
+    uint32_t regs[FSI_MASTER_NR_REGS];
+} FSIMasterState;
+
+
+#endif /* FSI_FSI_H */
diff --git a/include/hw/fsi/fsi-slave.h b/include/hw/fsi/fsi-slave.h
index bff807ff20..f5f23f4457 100644
--- a/include/hw/fsi/fsi-slave.h
+++ b/include/hw/fsi/fsi-slave.h
@@ -15,8 +15,8 @@
 #include <stdint.h>
 
 #define TYPE_FSI_SLAVE "fsi.slave"
-#define FSI_SLAVE(obj) \
-    OBJECT_CHECK(FSISlaveState, (obj), TYPE_FSI_SLAVE)
+OBJECT_DECLARE_SIMPLE_TYPE(FSISlaveState, FSI_SLAVE)
+
 #define FSI_SLAVE_CONTROL_NR_REGS ((0x40 >> 2) + 1)
 
 typedef struct FSISlaveState {
diff --git a/include/hw/fsi/fsi.h b/include/hw/fsi/fsi.h
new file mode 100644
index 0000000000..9c8dbe884f
--- /dev/null
+++ b/include/hw/fsi/fsi.h
@@ -0,0 +1,31 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM Flexible Service Interface
+ */
+#ifndef FSI_FSI_H
+#define FSI_FSI_H
+
+#include "hw/qdev-core.h"
+
+/*
+ * TODO: Maybe unwind this dependency with const links? Store a
+ * pointer in FSIBus?
+ */
+#include "hw/fsi/cfam.h"
+
+#define TYPE_FSI_BUS "fsi.bus"
+OBJECT_DECLARE_SIMPLE_TYPE(FSIBus, FSI_BUS)
+
+/* TODO: Figure out what's best with a point-to-point bus */
+typedef struct FSISlaveState FSISlaveState;
+
+typedef struct FSIBus {
+    BusState bus;
+
+    /* XXX: It's point-to-point, just instantiate the slave directly for now */
+    CFAMState slave;
+} FSIBus;
+
+#endif
