[RFC PATCH v3 07/13] 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 | 17 ++++++++++++-----
 hw/arm/virt.c            |  3 +++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index a222981737..9edd6385dc 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -57,14 +57,18 @@
 
 #define ARM_SPI_BASE 32
 
-static void acpi_dsdt_add_cpus(Aml *scope, int cpus)
+static void acpi_dsdt_add_cpus(Aml *scope, VirtMachineState *vms)
 {
     uint16_t i;
+    CPUArchIdList *possible_cpus = MACHINE(vms)->possible_cpus;
 
-    for (i = 0; i < 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);
     }
 }
@@ -470,6 +474,7 @@ 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));
@@ -480,7 +485,7 @@ 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));
@@ -495,7 +500,9 @@ 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));
@@ -599,7 +606,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, 
VirtMachineState *vms)
      * the RTC ACPI device at all when using UEFI.
      */
     scope = aml_scope("\\_SB");
-    acpi_dsdt_add_cpus(scope, ms->smp.cpus);
+    acpi_dsdt_add_cpus(scope, vms);
     acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
                        (irqmap[VIRT_UART] + ARM_SPI_BASE));
     if (vmc->acpi_expose_flash) {
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index d23b941020..b6cebb5549 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1977,6 +1977,9 @@ 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