blob: 2df7623d74d96e1e33d6d36a33d05f42d775337c [file] [log] [blame]
* Virtual Machine Generation ID Device
* Copyright (C) 2017 Skyport Systems.
* Author: Ben Warren <>
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qapi-commands-misc.h"
#include "qemu/module.h"
#include "hw/acpi/acpi.h"
#include "hw/acpi/aml-build.h"
#include "hw/acpi/vmgenid.h"
#include "hw/nvram/fw_cfg.h"
#include "hw/qdev-properties.h"
#include "migration/vmstate.h"
#include "sysemu/reset.h"
void vmgenid_build_acpi(VmGenIdState *vms, GArray *table_data, GArray *guid,
BIOSLinker *linker)
Aml *ssdt, *dev, *scope, *method, *addr, *if_ctx;
uint32_t vgia_offset;
QemuUUID guid_le;
/* Fill in the GUID values. These need to be converted to little-endian
* first, since that's what the guest expects
g_array_set_size(guid, VMGENID_FW_CFG_SIZE - ARRAY_SIZE(;
guid_le = qemu_uuid_bswap(vms->guid);
/* The GUID is written at a fixed offset into the fw_cfg file
* in order to implement the "OVMF SDT Header probe suppressor"
* see docs/specs/vmgenid.txt for more details
g_array_insert_vals(guid, VMGENID_GUID_OFFSET,,
/* Put this in a separate SSDT table */
ssdt = init_aml_allocator();
/* Reserve space for header */
acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));
/* Storage for the GUID address */
vgia_offset = table_data->len +
build_append_named_dword(ssdt->buf, "VGIA");
scope = aml_scope("\\_SB");
dev = aml_device("VGEN");
aml_append(dev, aml_name_decl("_HID", aml_string("QEMUVGID")));
aml_append(dev, aml_name_decl("_CID", aml_string("VM_Gen_Counter")));
aml_append(dev, aml_name_decl("_DDN", aml_string("VM_Gen_Counter")));
/* Simple status method to check that address is linked and non-zero */
method = aml_method("_STA", 0, AML_NOTSERIALIZED);
addr = aml_local(0);
aml_append(method, aml_store(aml_int(0xf), addr));
if_ctx = aml_if(aml_equal(aml_name("VGIA"), aml_int(0)));
aml_append(if_ctx, aml_store(aml_int(0), addr));
aml_append(method, if_ctx);
aml_append(method, aml_return(addr));
aml_append(dev, method);
/* the ADDR method returns two 32-bit words representing the lower and
* upper halves * of the physical address of the fw_cfg blob
* (holding the GUID)
method = aml_method("ADDR", 0, AML_NOTSERIALIZED);
addr = aml_local(0);
aml_append(method, aml_store(aml_package(2), addr));
aml_append(method, aml_store(aml_add(aml_name("VGIA"),
aml_index(addr, aml_int(0))));
aml_append(method, aml_store(aml_int(0), aml_index(addr, aml_int(1))));
aml_append(method, aml_return(addr));
aml_append(dev, method);
aml_append(scope, dev);
aml_append(ssdt, scope);
/* attach an ACPI notify */
method = aml_method("\\_GPE._E05", 0, AML_NOTSERIALIZED);
aml_append(method, aml_notify(aml_name("\\_SB.VGEN"), aml_int(0x80)));
aml_append(ssdt, method);
g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
/* Allocate guest memory for the Data fw_cfg blob */
bios_linker_loader_alloc(linker, VMGENID_GUID_FW_CFG_FILE, guid, 4096,
false /* page boundary, high memory */);
/* Patch address of GUID fw_cfg blob into the ADDR fw_cfg blob
* so QEMU can write the GUID there. The address is expected to be
* < 4GB, but write 64 bits anyway.
* The address that is patched in is offset in order to implement
* the "OVMF SDT Header probe suppressor"
* see docs/specs/vmgenid.txt for more details.
VMGENID_ADDR_FW_CFG_FILE, 0, sizeof(uint64_t),
/* Patch address of GUID fw_cfg blob into the AML so OSPM can retrieve
* and read it. Note that while we provide storage for 64 bits, only
* the least-signficant 32 get patched into AML.
ACPI_BUILD_TABLE_FILE, vgia_offset, sizeof(uint32_t),
build_header(linker, table_data,
(void *)(table_data->data + table_data->len - ssdt->buf->len),
"SSDT", ssdt->buf->len, 1, NULL, "VMGENID");
void vmgenid_add_fw_cfg(VmGenIdState *vms, FWCfgState *s, GArray *guid)
/* Create a read-only fw_cfg file for GUID */
fw_cfg_add_file(s, VMGENID_GUID_FW_CFG_FILE, guid->data,
/* Create a read-write fw_cfg file for Address */
fw_cfg_add_file_callback(s, VMGENID_ADDR_FW_CFG_FILE, NULL, NULL, NULL,
ARRAY_SIZE(vms->vmgenid_addr_le), false);
static void vmgenid_update_guest(VmGenIdState *vms)
Object *obj = object_resolve_path_type("", TYPE_ACPI_DEVICE_IF, NULL);
uint32_t vmgenid_addr;
QemuUUID guid_le;
if (obj) {
/* Write the GUID to guest memory */
memcpy(&vmgenid_addr, vms->vmgenid_addr_le, sizeof(vmgenid_addr));
vmgenid_addr = le32_to_cpu(vmgenid_addr);
/* A zero value in vmgenid_addr means that BIOS has not yet written
* the address
if (vmgenid_addr) {
/* QemuUUID has the first three words as big-endian, and expect
* that any GUIDs passed in will always be BE. The guest,
* however, will expect the fields to be little-endian.
* Perform a byte swap immediately before writing.
guid_le = qemu_uuid_bswap(vms->guid);
/* The GUID is written at a fixed offset into the fw_cfg file
* in order to implement the "OVMF SDT Header probe suppressor"
* see docs/specs/vmgenid.txt for more details.
/* Send _GPE.E05 event */
/* After restoring an image, we need to update the guest memory and notify
* it of a potential change to VM Generation ID
static int vmgenid_post_load(void *opaque, int version_id)
VmGenIdState *vms = opaque;
return 0;
static const VMStateDescription vmstate_vmgenid = {
.name = "vmgenid",
.version_id = 1,
.minimum_version_id = 1,
.post_load = vmgenid_post_load,
.fields = (VMStateField[]) {
VMSTATE_UINT8_ARRAY(vmgenid_addr_le, VmGenIdState, sizeof(uint64_t)),
static void vmgenid_handle_reset(void *opaque)
VmGenIdState *vms = VMGENID(opaque);
/* Clear the guest-allocated GUID address when the VM resets */
memset(vms->vmgenid_addr_le, 0, ARRAY_SIZE(vms->vmgenid_addr_le));
static void vmgenid_realize(DeviceState *dev, Error **errp)
VmGenIdState *vms = VMGENID(dev);
if (!bios_linker_loader_can_write_pointer()) {
error_setg(errp, "%s requires DMA write support in fw_cfg, "
"which this machine type does not provide", VMGENID_DEVICE);
/* Given that this function is executing, there is at least one VMGENID
* device. Check if there are several.
if (!find_vmgenid_dev()) {
error_setg(errp, "at most one %s device is permitted", VMGENID_DEVICE);
qemu_register_reset(vmgenid_handle_reset, vms);
static Property vmgenid_device_properties[] = {
static void vmgenid_device_class_init(ObjectClass *klass, void *data)
DeviceClass *dc = DEVICE_CLASS(klass);
dc->vmsd = &vmstate_vmgenid;
dc->realize = vmgenid_realize;
device_class_set_props(dc, vmgenid_device_properties);
dc->hotpluggable = false;
set_bit(DEVICE_CATEGORY_MISC, dc->categories);
static const TypeInfo vmgenid_device_info = {
.parent = TYPE_DEVICE,
.instance_size = sizeof(VmGenIdState),
.class_init = vmgenid_device_class_init,
static void vmgenid_register_types(void)
GuidInfo *qmp_query_vm_generation_id(Error **errp)
GuidInfo *info;
VmGenIdState *vms;
Object *obj = find_vmgenid_dev();
if (!obj) {
error_setg(errp, "VM Generation ID device not found");
return NULL;
vms = VMGENID(obj);
info = g_malloc0(sizeof(*info));
info->guid = qemu_uuid_unparse_strdup(&vms->guid);
return info;