[PATCH] target/s390x/kvm: Enable adapter interruption suppression again

[Thomas Huth <thuth@redhat.com>]

The AIS feature has been disabled late in the v2.10 development
cycle since there were some issues with migration (see commit
3f2d07b3b01ea61126b - "s390x/ais: for 2.10 stable: disable ais
facility"). We originally wanted to enable it again for newer
machine types, but apparently we forgot to do this so far. Let's
do it for the new s390-ccw-virtio-5.0 machine now.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1756946
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/s390x/s390-virtio-ccw.c         |  4 ++++
 include/hw/s390x/s390-virtio-ccw.h |  4 ++++
 target/s390x/kvm.c                 | 11 ++++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index e7eadd14e8..6f43136396 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -456,6 +456,7 @@ 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->kvm_ais_allowed = true;
     mc->init = ccw_init;
     mc->reset = s390_machine_reset;
     mc->hot_add_cpu = s390_hot_add_cpu;
@@ -662,6 +663,9 @@ static void ccw_machine_4_2_instance_options(MachineState *machine)
 
 static void ccw_machine_4_2_class_options(MachineClass *mc)
 {
+    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
+
+    s390mc->kvm_ais_allowed = false;
     ccw_machine_5_0_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index 8aa27199c9..f142d379c6 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -21,6 +21,9 @@
 #define S390_MACHINE_CLASS(klass) \
     OBJECT_CLASS_CHECK(S390CcwMachineClass, (klass), TYPE_S390_CCW_MACHINE)
 
+#define S390_CCW_MACHINE_OBJ_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(S390CcwMachineClass, obj, TYPE_S390_CCW_MACHINE)
+
 typedef struct S390CcwMachineState {
     /*< private >*/
     MachineState parent_obj;
@@ -40,6 +43,7 @@ typedef struct S390CcwMachineClass {
     bool cpu_model_allowed;
     bool css_migration_enabled;
     bool hpage_1m_allowed;
+    bool kvm_ais_allowed;
 } S390CcwMachineClass;
 
 /* runtime-instrumentation allowed by the machine */
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 15260aeb9a..4c1c8c0208 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -329,6 +329,8 @@ static void ccw_machine_class_foreach(ObjectClass *oc, void *opaque)
 
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
+    S390CcwMachineClass *smc = S390_CCW_MACHINE_OBJ_GET_CLASS(ms);
+
     object_class_foreach(ccw_machine_class_foreach, TYPE_S390_CCW_MACHINE,
                          false, NULL);
 
@@ -365,10 +367,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     /*
      * The migration interface for ais was introduced with kernel 4.13
      * but the capability itself had been active since 4.12. As migration
-     * support is considered necessary let's disable ais in the 2.10
-     * machine.
+     * support is considered necessary we only enable this for newer
+     * machine types and if KVM_CAP_S390_AIS_MIGRATION is available.
      */
-    /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */
+    if (smc->kvm_ais_allowed &&
+        kvm_check_extension(s, KVM_CAP_S390_AIS_MIGRATION)) {
+        kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0);
+    }
 
     kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
     return 0;
-- 
2.18.1