[PATCH RFC V3 03/29] hw/arm/virt: Limit number of possible vCPUs for unsupported Accel or GIC Type

[Salil Mehta]

If Virtual CPU Hotplug support does not exist on a particular Accel platform or
ARM GIC version, we should limit the possible vCPUs to those available during
boot time (i.e SMP CPUs) and explicitly disable Virtual CPU Hotplug support.

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 11fc7fc318..3e1c4d2d2f 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2082,8 +2082,6 @@ 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()
      * to create a VM with the right number of IPA bits.
@@ -2098,7 +2096,7 @@ 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);
@@ -2113,6 +2111,43 @@ 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() || 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,
@@ -2147,31 +2182,6 @@ 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