[RFC PATCH v2 3/6] hw/arm/virt-acpi-build: Distinguish possible and present cpus

[Yanan Wang]

From: Ying Fang <fangying1@huawei.com>

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>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
---
 hw/arm/virt-acpi-build.c | 14 ++++++++++----
 hw/arm/virt.c            |  3 +++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index f5a2b2d4cb..2ad5dad1bf 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 f4ae60ded9..3e5d9b6f26 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2063,6 +2063,9 @@ static void machvirt_init(MachineState *machine)
         }
 
         qdev_realize(DEVICE(cpuobj), NULL, &error_fatal);
+
+        /* Initialize cpu member here since cpu hotplug is not supported yet */
+        machine->possible_cpus->cpus[n].cpu = cpuobj;
         object_unref(cpuobj);
     }
     fdt_add_timer_nodes(vms);
-- 
2.19.1