[PATCH V14 4/7] hw/acpi: Update GED _EVT method AML with CPU scan

[Salil Mehta]

OSPM evaluates _EVT method to map the event. The CPU hotplug event eventually
results in start of the CPU scan. Scan figures out the CPU and the kind of
event(plug/unplug) and notifies it back to the guest. Update the GED AML _EVT
method with the call to method \\_SB.CPUS.CSCN (via \\_SB.GED.CSCN)

Architecture specific code [1] might initialize its CPUs AML code by calling
common function build_cpus_aml() like below for ARM:

build_cpus_aml(scope, ms, opts, xx_madt_cpu_entry, memmap[VIRT_CPUHP_ACPI].base,
               "\\_SB", "\\_SB.GED.CSCN", AML_SYSTEM_MEMORY);

[1] 
https://lore.kernel.org/qemu-devel/20240613233639.202896-13-salil.mehta@huawei.com/

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Xianglai Li <lixianglai@loongson.cn>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
Tested-by: Zhao Liu <zhao1.liu@intel.com>
---
 hw/acpi/cpu.c                  | 2 +-
 hw/acpi/generic_event_device.c | 4 ++++
 include/hw/acpi/cpu.h          | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index ee99290800..57906efebf 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -323,7 +323,7 @@ const VMStateDescription vmstate_cpu_hotplug = {
 #define CPUHP_RES_DEVICE  "PRES"
 #define CPU_LOCK          "CPLK"
 #define CPU_STS_METHOD    "CSTA"
-#define CPU_SCAN_METHOD   "CSCN"
+#define CPU_SCAN_METHOD   ACPI_CPU_SCAN_METHOD
 #define CPU_NOTIFY_METHOD "CTFY"
 #define CPU_EJECT_METHOD  "CEJ0"
 #define CPU_OST_METHOD    "COST"
diff --git a/hw/acpi/generic_event_device.c b/hw/acpi/generic_event_device.c
index e762fc6128..cbd2e2d26e 100644
--- a/hw/acpi/generic_event_device.c
+++ b/hw/acpi/generic_event_device.c
@@ -109,6 +109,10 @@ void build_ged_aml(Aml *table, const char *name, 
HotplugHandler *hotplug_dev,
                 aml_append(if_ctx, aml_call0(MEMORY_DEVICES_CONTAINER "."
                                              MEMORY_SLOT_SCAN_METHOD));
                 break;
+            case ACPI_GED_CPU_HOTPLUG_EVT:
+                aml_append(if_ctx, aml_call0("\\_SB."GED_DEVICE"."
+                                             ACPI_CPU_SCAN_METHOD));
+                break;
             case ACPI_GED_PWR_DOWN_EVT:
                 aml_append(if_ctx,
                            aml_notify(aml_name(ACPI_POWER_BUTTON_DEVICE),
diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
index df87b15997..451dda448a 100644
--- a/include/hw/acpi/cpu.h
+++ b/include/hw/acpi/cpu.h
@@ -20,6 +20,7 @@
 #include "hw/hotplug.h"
 
 #define ACPI_CPU_HOTPLUG_REG_LEN 12
+#define ACPI_CPU_SCAN_METHOD "CSCN"
 
 typedef struct AcpiCpuStatus {
     CPUState *cpu;
-- 
2.34.1