For unsupported acceleration types and GIC versions, explicitly disable vCPU
hotplug support and limit the number of possible vCPUs to those available at
boot time (i.e., SMP CPUs). This flag will be referenced at various points in
the code to verify the presence of vCPU hotplug functionality on this machine.

Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 hw/arm/virt.c | 66 +++++++++++++++++++++++++++++----------------------
 1 file changed, 38 insertions(+), 28 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 8ff7e109dd..827a796ed6 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2108,8 +2108,6 @@ static void machvirt_init(MachineState *machine)
     unsigned int smp_cpus = machine->smp.cpus;
     unsigned int max_cpus = machine->smp.max_cpus;
 
-    possible_cpus = mc->possible_cpu_arch_ids(machine);
-
     /*
      * In accelerated mode, the memory map is computed earlier in kvm_type()
      * for Linux, or hvf_get_physical_address_range() for macOS to create a
@@ -2125,7 +2123,7 @@ static void machvirt_init(MachineState *machine)
          * we are about to deal with. Once this is done, get rid of
          * the object.
          */
-        cpuobj = object_new(possible_cpus->cpus[0].type);
+        cpuobj = object_new(machine->cpu_type);
         armcpu = ARM_CPU(cpuobj);
 
         pa_bits = arm_pamax(armcpu);
@@ -2140,6 +2138,43 @@ static void machvirt_init(MachineState *machine)
      */
     finalize_gic_version(vms);
 
+    /*
+     * The maximum number of CPUs depends on the GIC version, or on how
+     * many redistributors we can fit into the memory map (which in turn
+     * depends on whether this is a GICv3 or v4).
+     */
+    if (vms->gic_version == VIRT_GIC_VERSION_2) {
+        virt_max_cpus = GIC_NCPU;
+    } else {
+        virt_max_cpus = virt_redist_capacity(vms, VIRT_GIC_REDIST);
+        if (vms->highmem_redists) {
+            virt_max_cpus += virt_redist_capacity(vms, VIRT_HIGH_GIC_REDIST2);
+        }
+    }
+
+    if ((tcg_enabled() && !qemu_tcg_mttcg_enabled()) || hvf_enabled() ||
+        qtest_enabled() || (vms->gic_version < VIRT_GIC_VERSION_3)) {
+        max_cpus = machine->smp.max_cpus = smp_cpus;
+        mc->has_hotpluggable_cpus = false;
+        if (vms->gic_version >= VIRT_GIC_VERSION_3) {
+            warn_report("cpu hotplug feature has been disabled");
+        }
+    }
+
+    if (max_cpus > virt_max_cpus) {
+        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
+                     "supported by machine 'mach-virt' (%d)",
+                     max_cpus, virt_max_cpus);
+        if (vms->gic_version != VIRT_GIC_VERSION_2 && !vms->highmem_redists) {
+            error_printf("Try 'highmem-redists=on' for more CPUs\n");
+        }
+
+        exit(1);
+    }
+
+    /* uses smp.max_cpus to initialize all possible vCPUs */
+    possible_cpus = mc->possible_cpu_arch_ids(machine);
+
     if (vms->secure) {
         /*
          * The Secure view of the world is the same as the NonSecure,
@@ -2174,31 +2209,6 @@ static void machvirt_init(MachineState *machine)
         vms->psci_conduit = QEMU_PSCI_CONDUIT_HVC;
     }
 
-    /*
-     * The maximum number of CPUs depends on the GIC version, or on how
-     * many redistributors we can fit into the memory map (which in turn
-     * depends on whether this is a GICv3 or v4).
-     */
-    if (vms->gic_version == VIRT_GIC_VERSION_2) {
-        virt_max_cpus = GIC_NCPU;
-    } else {
-        virt_max_cpus = virt_redist_capacity(vms, VIRT_GIC_REDIST);
-        if (vms->highmem_redists) {
-            virt_max_cpus += virt_redist_capacity(vms, VIRT_HIGH_GIC_REDIST2);
-        }
-    }
-
-    if (max_cpus > virt_max_cpus) {
-        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
-                     "supported by machine 'mach-virt' (%d)",
-                     max_cpus, virt_max_cpus);
-        if (vms->gic_version != VIRT_GIC_VERSION_2 && !vms->highmem_redists) {
-            error_printf("Try 'highmem-redists=on' for more CPUs\n");
-        }
-
-        exit(1);
-    }
-
     if (vms->secure && (kvm_enabled() || hvf_enabled())) {
         error_report("mach-virt: %s does not support providing "
                      "Security extensions (TrustZone) to the guest CPU",
-- 
2.34.1