[RFC PATCH 3/5] hw/arm/virt-acpi-build: distinguish possible and present cpus

[Ying Fang]

When building ACPI tables regarding CPUs we should always build
them for the number of possible CPUs, not the number of present
CPUs. We then ensure only the present CPUs are enabled in madt.
Furthermore, it is also needed if we are going to support CPU
hotplug in the future.

This patch is a rework based on Andrew Jones's contribution at
https://lists.gnu.org/archive/html/qemu-arm/2018-07/msg00076.html

Signed-off-by: Ying Fang <fangying1@huawei.com>
---
 hw/arm/virt-acpi-build.c | 14 ++++++++++----
 hw/arm/virt.c            |  2 ++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index f9c9df916c..bb91152fe2 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -61,13 +61,16 @@
 
 static void acpi_dsdt_add_cpus(Aml *scope, VirtMachineState *vms)
 {
-    MachineState *ms = MACHINE(vms);
+    CPUArchIdList *possible_cpus = MACHINE(vms)->possible_cpus;
     uint16_t i;
 
-    for (i = 0; i < ms->smp.cpus; i++) {
+    for (i = 0; i < possible_cpus->len; i++) {
         Aml *dev = aml_device("C%.03X", i);
         aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0007")));
         aml_append(dev, aml_name_decl("_UID", aml_int(i)));
+        if (possible_cpus->cpus[i].cpu == NULL) {
+            aml_append(dev, aml_name_decl("_STA", aml_int(0)));
+        }
         aml_append(scope, dev);
     }
 }
@@ -479,6 +482,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
     const int *irqmap = vms->irqmap;
     AcpiMadtGenericDistributor *gicd;
     AcpiMadtGenericMsiFrame *gic_msi;
+    CPUArchIdList *possible_cpus = MACHINE(vms)->possible_cpus;
     int i;
 
     acpi_data_push(table_data, sizeof(AcpiMultipleApicTable));
@@ -489,7 +493,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
     gicd->base_address = cpu_to_le64(memmap[VIRT_GIC_DIST].base);
     gicd->version = vms->gic_version;
 
-    for (i = 0; i < MACHINE(vms)->smp.cpus; i++) {
+    for (i = 0; i < possible_cpus->len; i++) {
         AcpiMadtGenericCpuInterface *gicc = acpi_data_push(table_data,
                                                            sizeof(*gicc));
         ARMCPU *armcpu = ARM_CPU(qemu_get_cpu(i));
@@ -504,7 +508,9 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
         gicc->cpu_interface_number = cpu_to_le32(i);
         gicc->arm_mpidr = cpu_to_le64(armcpu->mp_affinity);
         gicc->uid = cpu_to_le32(i);
-        gicc->flags = cpu_to_le32(ACPI_MADT_GICC_ENABLED);
+        if (possible_cpus->cpus[i].cpu != NULL) {
+            gicc->flags = cpu_to_le32(ACPI_MADT_GICC_ENABLED);
+        }
 
         if (arm_feature(&armcpu->env, ARM_FEATURE_PMU)) {
             gicc->performance_interrupt = cpu_to_le32(PPI(VIRTUAL_PMU_IRQ));
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index c133b342b8..75659502e2 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2047,6 +2047,8 @@ static void machvirt_init(MachineState *machine)
 
         qdev_realize(DEVICE(cpuobj), NULL, &error_fatal);
         object_unref(cpuobj);
+        /* Initialize cpu member here since cpu hotplug is not supported yet */
+        machine->possible_cpus->cpus[n].cpu = cpuobj;
     }
     fdt_add_timer_nodes(vms);
     fdt_add_cpu_nodes(vms);
-- 
2.23.0