i386/acpi-build: support hotplug of VCPU with APIC ID 0xFF

Building on the previous patch, raise the maximal count of processor
objects / NTFY branches / CPON elements from 255 to 256. This allows the
VCPU with APIC ID 0xFF to be hotplugged.
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/i386/acpi-build.c

@@ -999,11 +999,16 @@ build_ssdt(GArray *table_data, GArray *linker,
            AcpiCpuInfo *cpu, AcpiPmInfo *pm, AcpiMiscInfo *misc,
            PcPciInfo *pci, PcGuestInfo *guest_info)
 {
-    int acpi_cpus = MIN(0xff, guest_info->apic_id_limit);
+    unsigned acpi_cpus = guest_info->apic_id_limit;
     int ssdt_start = table_data->len;
     uint8_t *ssdt_ptr;
     int i;
 
+    /* The current AML generator can cover the APIC ID range [0..255],
+     * inclusive, for VCPU hotplug. */
+    QEMU_BUILD_BUG_ON(ACPI_CPU_HOTPLUG_ID_LIMIT > 256);
+    g_assert(acpi_cpus <= ACPI_CPU_HOTPLUG_ID_LIMIT);
+
     /* Copy header and patch values in the S3_ / S4_ / S5_ packages */
     ssdt_ptr = acpi_data_push(table_data, sizeof(ssdp_misc_aml));
     memcpy(ssdt_ptr, ssdp_misc_aml, sizeof(ssdp_misc_aml));