Changes are required during the building of the MADT table by QEMU to
accommodate disabled possible vCPUs. This information will be used by the guest
kernel to size up its resources during boot time. The pre-sizing of the guest
kernel based on possible vCPUs will facilitate the hotplug of the disabled
vCPUs.

This change also addresses ACPI MADT GIC CPU interface flag-related changes
recently introduced in the UEFI ACPI 6.5 specification, which allows deferred
virtual CPU online'ing in the guest kernel.

Link: https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#gic-cpu-interface-gicc-structure

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>
---
 hw/arm/virt-acpi-build.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 2d44567df5..4b4906f407 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -657,6 +657,29 @@ static void build_append_gicr(GArray *table_data, uint64_t base, uint32_t size)
     build_append_int_noprefix(table_data, size, 4); /* Discovery Range Length */
 }
 
+static uint32_t virt_acpi_get_gicc_flags(CPUState *cpu)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
+
+    /* can only exist in 'enabled' state */
+    if (!mc->has_hotpluggable_cpus) {
+        return 1;
+    }
+
+    /*
+     * ARM GIC CPU Interface can be 'online-capable' or 'enabled' at boot
+     * We MUST set 'online-capable' bit for all hotpluggable CPUs except the
+     * first/boot CPU. Cold-booted CPUs without 'Id' can also be unplugged.
+     * Though as-of-now this is only used as a debugging feature.
+     *
+     *   UEFI ACPI Specification 6.5
+     *   Section: 5.2.12.14. GIC CPU Interface (GICC) Structure
+     *   Table:   5.37 GICC CPU Interface Flags
+     *   Link: https://uefi.org/specs/ACPI/6.5
+     */
+    return cpu && !cpu->cpu_index ? 1 : (1 << 3);
+}
+
 static void
 build_madt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
 {
@@ -683,12 +706,13 @@ build_madt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
     build_append_int_noprefix(table_data, vms->gic_version, 1);
     build_append_int_noprefix(table_data, 0, 3);   /* Reserved */
 
-    for (i = 0; i < MACHINE(vms)->smp.cpus; i++) {
-        ARMCPU *armcpu = ARM_CPU(qemu_get_cpu(i));
+    for (i = 0; i < MACHINE(vms)->smp.max_cpus; i++) {
+        CPUState *cpu = qemu_get_possible_cpu(i);
         uint64_t physical_base_address = 0, gich = 0, gicv = 0;
         uint32_t vgic_interrupt = vms->virt ? ARCH_GIC_MAINT_IRQ : 0;
-        uint32_t pmu_interrupt = arm_feature(&armcpu->env, ARM_FEATURE_PMU) ?
-                                             VIRTUAL_PMU_IRQ : 0;
+        uint32_t pmu_interrupt = vms->pmu ? VIRTUAL_PMU_IRQ : 0;
+        uint32_t flags = virt_acpi_get_gicc_flags(cpu);
+        uint64_t mpidr = qemu_get_cpu_archid(i);
 
         if (vms->gic_version == VIRT_GIC_VERSION_2) {
             physical_base_address = memmap[VIRT_GIC_CPU].base;
@@ -703,7 +727,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
         build_append_int_noprefix(table_data, i, 4);    /* GIC ID */
         build_append_int_noprefix(table_data, i, 4);    /* ACPI Processor UID */
         /* Flags */
-        build_append_int_noprefix(table_data, 1, 4);    /* Enabled */
+        build_append_int_noprefix(table_data, flags, 4);
         /* Parking Protocol Version */
         build_append_int_noprefix(table_data, 0, 4);
         /* Performance Interrupt GSIV */
@@ -717,7 +741,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
         build_append_int_noprefix(table_data, vgic_interrupt, 4);
         build_append_int_noprefix(table_data, 0, 8);    /* GICR Base Address*/
         /* MPIDR */
-        build_append_int_noprefix(table_data, arm_cpu_mp_affinity(armcpu), 8);
+        build_append_int_noprefix(table_data, mpidr, 8);
         /* Processor Power Efficiency Class */
         build_append_int_noprefix(table_data, 0, 1);
         /* Reserved */
-- 
2.34.1