ich9, piix4: add property, smm-compat, to keep compatibility of SMM

The following patch will introduce incompatible behavior of SMM.
Introduce a property to keep the old behavior for compatibility.
To enable smm compat, use "-global ICH9-LPC.smm-compat=on" or
"-global PIIX4_PM.smm-compat=on"

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <47254ae0b8c6cc6945422978b6b2af2d213ef891.1613615732.git.isaku.yamahata@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

hw/acpi/piix4.c

@@ -74,6 +74,7 @@ struct PIIX4PMState {
     qemu_irq irq;
     qemu_irq smi_irq;
     int smm_enabled;
+    bool smm_compat;
     Notifier machine_ready;
     Notifier powerdown_notifier;
 
@@ -642,6 +643,7 @@ static Property piix4_pm_properties[] = {
                      use_acpi_root_pci_hotplug, true),
     DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
                      acpi_memory_hotplug.is_enabled, true),
+    DEFINE_PROP_BOOL("smm-compat", PIIX4PMState, smm_compat, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 

hw/isa/lpc_ich9.c

@@ -775,6 +775,7 @@ static const VMStateDescription vmstate_ich9_lpc = {
 
 static Property ich9_lpc_properties[] = {
     DEFINE_PROP_BOOL("noreboot", ICH9LPCState, pin_strap.spkr_hi, true),
+    DEFINE_PROP_BOOL("smm-compat", ICH9LPCState, pm.smm_compat, false),
     DEFINE_PROP_BIT64("x-smi-broadcast", ICH9LPCState, smi_host_features,
                       ICH9_LPC_SMI_F_BROADCAST_BIT, true),
     DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState, smi_host_features,

include/hw/acpi/ich9.h

@@ -59,6 +59,7 @@ typedef struct ICH9LPCPMRegs {
     uint8_t disable_s4;
     uint8_t s4_val;
     uint8_t smm_enabled;
+    bool smm_compat;
     bool enable_tco;
     TCOIORegs tco_regs;
 } ICH9LPCPMRegs;