s390x/cpu topology: add max_threads machine class attribute

The S390 CPU topology accepts the smp.threads argument while
in reality it does not effectively allow multthreading.

Let's keep this behavior for machines older than 7.2 and
refuse to use threads in newer machines until multithreading
is really exposed to the guest by the machine.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20221103170150.20789-3-pmorel@linux.ibm.com>
[thuth: Small fixes to the commit description]
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 196773c8333d15134c056f101a0f1546c273bb2e..560ddbb6fbd3c2d8808a57041412a596ff6b5bbb 100644 (file)
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -85,8 +85,15 @@ out:
 static void s390_init_cpus(MachineState *machine)
 {
     MachineClass *mc = MACHINE_GET_CLASS(machine);
+    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
     int i;
 
+    if (machine->smp.threads > s390mc->max_threads) {
+        error_report("S390 does not support more than %d threads.",
+                     s390mc->max_threads);
+        exit(1);
+    }
+
     /* initialize possible_cpus */
     mc->possible_cpu_arch_ids(machine);
 
@@ -731,6 +738,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data)
     s390mc->cpu_model_allowed = true;
     s390mc->css_migration_enabled = true;
     s390mc->hpage_1m_allowed = true;
+    s390mc->max_threads = 1;
     mc->init = ccw_init;
     mc->reset = s390_machine_reset;
     mc->block_default_type = IF_VIRTIO;
@@ -859,8 +867,11 @@ static void ccw_machine_7_1_instance_options(MachineState *machine)
 
 static void ccw_machine_7_1_class_options(MachineClass *mc)
 {
+    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
+
     ccw_machine_7_2_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_7_1, hw_compat_7_1_len);
+    s390mc->max_threads = S390_MAX_CPUS;
 }
 DEFINE_CCW_MACHINE(7_1, "7.1", false);
 

diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index 8a0090a0719a9dddb2df52f334eb86a61888d236..4f8a39abda4689dd1b276f9e9a436e8851ed72b2 100644 (file)
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -40,6 +40,7 @@ struct S390CcwMachineClass {
     bool cpu_model_allowed;
     bool css_migration_enabled;
     bool hpage_1m_allowed;
+    int max_threads;
 };
 
 /* runtime-instrumentation allowed by the machine */