diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
index 8c738c7a2b..b9d1ac3fad 100644
--- a/include/hw/cxl/cxl.h
+++ b/include/hw/cxl/cxl.h
@@ -12,5 +12,6 @@
#include "cxl_pci.h"
#include "cxl_component.h"
+#include "cxl_device.h"
#endif
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
new file mode 100644
index 0000000000..9513aaac77
--- /dev/null
+++ b/include/hw/cxl/cxl_device.h
@@ -0,0 +1,166 @@
+/*
+ * QEMU CXL Devices
+ *
+ * Copyright (c) 2020 Intel
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See the
+ * COPYING file in the top-level directory.
+ */
+
+#ifndef CXL_DEVICE_H
+#define CXL_DEVICE_H
+
+#include "hw/register.h"
+
+/*
+ * The following is how a CXL device's Memory Device registers are laid out.
+ * The only requirement from the spec is that the capabilities array and the
+ * capability headers start at offset 0 and are contiguously packed. The headers
+ * themselves provide offsets to the register fields. For this emulation, the
+ * actual registers * will start at offset 0x80 (m == 0x80). No secondary
+ * mailbox is implemented which means that the offset of the start of the
+ * mailbox payload (n) is given by
+ * n = m + sizeof(mailbox registers) + sizeof(device registers).
+ *
+ * +---------------------------------+
+ * | |
+ * | Memory Device Registers |
+ * | |
+ * n + PAYLOAD_SIZE_MAX -----------------------------------
+ * ^ | |
+ * | | |
+ * | | |
+ * | | |
+ * | | |
+ * | | Mailbox Payload |
+ * | | |
+ * | | |
+ * | | |
+ * n -----------------------------------
+ * ^ | Mailbox Registers |
+ * | | |
+ * | -----------------------------------
+ * | | |
+ * | | Device Registers |
+ * | | |
+ * m ---------------------------------->
+ * ^ | Memory Device Capability Header|
+ * | -----------------------------------
+ * | | Mailbox Capability Header |
+ * | -----------------------------------
+ * | | Device Capability Header |
+ * | -----------------------------------
+ * | | Device Cap Array Register |
+ * 0 +---------------------------------+
+ *
+ */
+
+#define CXL_DEVICE_CAP_HDR1_OFFSET 0x10 /* Figure 138 */
+#define CXL_DEVICE_CAP_REG_SIZE 0x10 /* 8.2.8.2 */
+#define CXL_DEVICE_CAPS_MAX 4 /* 8.2.8.2.1 + 8.2.8.5 */
+
+#define CXL_DEVICE_STATUS_REGISTERS_OFFSET 0x80 /* Read comment above */
+#define CXL_DEVICE_STATUS_REGISTERS_LENGTH 0x8 /* 8.2.8.3.1 */
+
+#define CXL_MAILBOX_REGISTERS_OFFSET \
+ (CXL_DEVICE_STATUS_REGISTERS_OFFSET + CXL_DEVICE_STATUS_REGISTERS_LENGTH)
+#define CXL_MAILBOX_REGISTERS_SIZE 0x20 /* 8.2.8.4, Figure 139 */
+#define CXL_MAILBOX_PAYLOAD_SHIFT 11
+#define CXL_MAILBOX_MAX_PAYLOAD_SIZE (1 << CXL_MAILBOX_PAYLOAD_SHIFT)
+#define CXL_MAILBOX_REGISTERS_LENGTH \
+ (CXL_MAILBOX_REGISTERS_SIZE + CXL_MAILBOX_MAX_PAYLOAD_SIZE)
+
+typedef struct cxl_device_state {
+ MemoryRegion device_registers;
+
+ /* mmio for device capabilities array - 8.2.8.2 */
+ MemoryRegion device;
+ MemoryRegion caps;
+
+ /* mmio for the mailbox registers 8.2.8.4 */
+ MemoryRegion mailbox;
+
+ /* memory region for persistent memory, HDM */
+ uint64_t pmem_size;
+} CXLDeviceState;
+
+/* Initialize the register block for a device */
+void cxl_device_register_block_init(Object *obj, CXLDeviceState *dev);
+
+/* Set up default values for the register block */
+void cxl_device_register_init_common(CXLDeviceState *dev);
+
+/*
+ * CXL 2.0 - 8.2.8.1 including errata F4
+ * Documented as a 128 bit register, but 64 bit accesses and the second
+ * 64 bits are currently reserved.
+ */
+REG64(CXL_DEV_CAP_ARRAY, 0) /* Documented as 128 bit register but 64 byte accesses */
+ FIELD(CXL_DEV_CAP_ARRAY, CAP_ID, 0, 16)
+ FIELD(CXL_DEV_CAP_ARRAY, CAP_VERSION, 16, 8)
+ FIELD(CXL_DEV_CAP_ARRAY, CAP_COUNT, 32, 16)
+
+/*
+ * Helper macro to initialize capability headers for CXL devices.
+ *
+ * In the 8.2.8.2, this is listed as a 128b register, but in 8.2.8, it says:
+ * > No registers defined in Section 8.2.8 are larger than 64-bits wide so that
+ * > is the maximum access size allowed for these registers. If this rule is not
+ * > followed, the behavior is undefined
+ *
+ * CXL 2.0 Errata F4 states futher that the layouts in the specification are
+ * shown as greater than 128 bits, but implementations are expected to
+ * use any size of access up to 64 bits.
+ *
+ * Here we've chosen to make it 4 dwords. The spec allows any pow2 multiple
+ * access to be used for a register up to 64 bits.
+ */
+#define CXL_DEVICE_CAPABILITY_HEADER_REGISTER(n, offset) \
+ REG32(CXL_DEV_##n##_CAP_HDR0, offset) \
+ FIELD(CXL_DEV_##n##_CAP_HDR0, CAP_ID, 0, 16) \
+ FIELD(CXL_DEV_##n##_CAP_HDR0, CAP_VERSION, 16, 8) \
+ REG32(CXL_DEV_##n##_CAP_HDR1, offset + 4) \
+ FIELD(CXL_DEV_##n##_CAP_HDR1, CAP_OFFSET, 0, 32) \
+ REG32(CXL_DEV_##n##_CAP_HDR2, offset + 8) \
+ FIELD(CXL_DEV_##n##_CAP_HDR2, CAP_LENGTH, 0, 32)
+
+CXL_DEVICE_CAPABILITY_HEADER_REGISTER(DEVICE_STATUS, CXL_DEVICE_CAP_HDR1_OFFSET)
+CXL_DEVICE_CAPABILITY_HEADER_REGISTER(MAILBOX, CXL_DEVICE_CAP_HDR1_OFFSET + \
+ CXL_DEVICE_CAP_REG_SIZE)
+
+/* CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register */
+REG32(CXL_DEV_MAILBOX_CAP, 0)
+ FIELD(CXL_DEV_MAILBOX_CAP, PAYLOAD_SIZE, 0, 5)
+ FIELD(CXL_DEV_MAILBOX_CAP, INT_CAP, 5, 1)
+ FIELD(CXL_DEV_MAILBOX_CAP, BG_INT_CAP, 6, 1)
+ FIELD(CXL_DEV_MAILBOX_CAP, MSI_N, 7, 4)
+
+/* CXL 2.0 8.2.8.4.4 Mailbox Control Register */
+REG32(CXL_DEV_MAILBOX_CTRL, 4)
+ FIELD(CXL_DEV_MAILBOX_CTRL, DOORBELL, 0, 1)
+ FIELD(CXL_DEV_MAILBOX_CTRL, INT_EN, 1, 1)
+ FIELD(CXL_DEV_MAILBOX_CTRL, BG_INT_EN, 2, 1)
+
+/* CXL 2.0 8.2.8.4.5 Command Register */
+REG64(CXL_DEV_MAILBOX_CMD, 8)
+ FIELD(CXL_DEV_MAILBOX_CMD, COMMAND, 0, 8)
+ FIELD(CXL_DEV_MAILBOX_CMD, COMMAND_SET, 8, 8)
+ FIELD(CXL_DEV_MAILBOX_CMD, LENGTH, 16, 20)
+
+/* CXL 2.0 8.2.8.4.6 Mailbox Status Register */
+REG64(CXL_DEV_MAILBOX_STS, 0x10)
+ FIELD(CXL_DEV_MAILBOX_STS, BG_OP, 0, 1)
+ FIELD(CXL_DEV_MAILBOX_STS, ERRNO, 32, 16)
+ FIELD(CXL_DEV_MAILBOX_STS, VENDOR_ERRNO, 48, 16)
+
+/* CXL 2.0 8.2.8.4.7 Background Command Status Register */
+REG64(CXL_DEV_BG_CMD_STS, 0x18)
+ FIELD(CXL_DEV_BG_CMD_STS, OP, 0, 16)
+ FIELD(CXL_DEV_BG_CMD_STS, PERCENTAGE_COMP, 16, 7)
+ FIELD(CXL_DEV_BG_CMD_STS, RET_CODE, 32, 16)
+ FIELD(CXL_DEV_BG_CMD_STS, VENDOR_RET_CODE, 48, 16)
+
+/* CXL 2.0 8.2.8.4.8 Command Payload Registers */
+REG32(CXL_DEV_CMD_PAYLOAD, 0x20)
+
+#endif