On 16/01/2020 13.28, David Hildenbrand wrote: > On 16.01.20 13:26, Thomas Huth wrote: >> On 16/01/2020 13.23, David Hildenbrand wrote: >>> On 16.01.20 13:20, Thomas Huth wrote: >>>> 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 <th...@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; >>>> >>> >>> We have ri_allowed(), cpu_model_allowed(), hpage_1m_allowed(). >>> >>> Care to create a similar wrapper? >> >> Honestly, why do we need these wrappers at all? They look cumbersome to >> me. I'd rather remove them in case they are not urgently needed (so far >> I don't see the point... could someone enlighten me why we have them?). > > I assume to minimize the number of places you have to lookup the > machine/machine class.
I don't think that any of these functions is performance critical, since they are only used during the initialization phase... But looking more closely, cpu_model_allowed() and hpage_1m_allowed() are used in functions where the current machine state / class is not directly available, so the wrappers indeed make sense there. We could remove the ri_allowed() wrapper, though, since this is also only used in kvm_arch_init() where the machine state is easily available. Thomas