pc: use new CPU hotplug interface since 2.7 machine type

For compatibility reasons PC/Q35 will start with legacy
CPU hotplug interface by default but with new CPU hotplug
AML code since 2.7 machine type. That way legacy firmware
that doesn't use QEMU generated ACPI tables will be
able to continue using legacy CPU hotplug interface.

While new machine type, with firmware supporting QEMU
provided ACPI tables, will generate new CPU hotplug AML,
which will switch to new CPU hotplug interface when
guest OS executes its _INI method on ACPI tables
loading.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
index 858244a661..2adc246b00 100644
--- a/hw/acpi/piix4.c
+++ b/hw/acpi/piix4.c
@@ -276,6 +276,32 @@ static const VMStateDescription vmstate_memhp_state = {
     }
 };
 
+static bool vmstate_test_use_cpuhp(void *opaque)
+{
+    PIIX4PMState *s = opaque;
+    return !s->cpu_hotplug_legacy;
+}
+
+static int vmstate_cpuhp_pre_load(void *opaque)
+{
+    Object *obj = OBJECT(opaque);
+    object_property_set_bool(obj, false, "cpu-hotplug-legacy", &error_abort);
+    return 0;
+}
+
+static const VMStateDescription vmstate_cpuhp_state = {
+    .name = "piix4_pm/cpuhp",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .needed = vmstate_test_use_cpuhp,
+    .pre_load = vmstate_cpuhp_pre_load,
+    .fields      = (VMStateField[]) {
+        VMSTATE_CPU_HOTPLUG(cpuhp_state, PIIX4PMState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 /* qemu-kvm 1.2 uses version 3 but advertised as 2
  * To support incoming qemu-kvm 1.2 migration, change version_id
  * and minimum_version_id to 2 below (which breaks migration from
@@ -310,6 +336,7 @@ static const VMStateDescription vmstate_acpi = {
     },
     .subsections = (const VMStateDescription*[]) {
          &vmstate_memhp_state,
+         &vmstate_cpuhp_state,
          NULL
     }
 };
@@ -585,6 +612,11 @@ static void piix4_set_cpu_hotplug_legacy(Object *obj, bool value, Error **errp)
 {
     PIIX4PMState *s = PIIX4_PM(obj);
 
+    assert(!value);
+    if (s->cpu_hotplug_legacy && value == false) {
+        acpi_switch_to_modern_cphp(&s->gpe_cpu, &s->cpuhp_state,
+                                   PIIX4_CPU_HOTPLUG_IO_BASE);
+    }
     s->cpu_hotplug_legacy = value;
 }