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

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 16.01.20 13:55, Thomas Huth wrote:
> On 16/01/2020 13.50, Cornelia Huck wrote:
>> On Thu, 16 Jan 2020 13:20:26 +0100
>> Thomas Huth <thuth@redhat.com> 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 <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(-)
>>>
>>
>>> @@ -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
>>
>> s/necessary we only enable this/necessary, we only try to enable this/
>>
>>> +     * machine types and if KVM_CAP_S390_AIS_MIGRATION is available.
>>
>> maybe s/and if/if/
> 
> Sure ... could you fix it up when picking up the patch (in case I don't
> have to respin), or do you want me to send a v2?
> 
>>>       */
>>> -    /* 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;
>>
>> Looks good.
>>
>> Remind me again: ais only made a difference for pci devices, right? Is
>> it enough to give this a quick whirl with virtio-pci devices?
> 
> I don't remember the details, Christian, could you please answer this
> question?

Yes, IIRC AIS was there for PCI, but not for Crypto or virtio.
The patch looks sane, but it would be good if someone could try
the AIS stuff.

Matt, can you have a look?