Re: [PATCH v2 1/2] target/s390x/kvm: Turn KVM_CAP_SYNC_REGS into a hard requirement

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

Am 10.10.23 um 13:12 schrieb Thomas Huth:
> On 10/10/2023 13.02, Christian Borntraeger wrote:
>>
>>
>> Am 09.10.23 um 19:07 schrieb Thomas Huth:
>>> Since we already require at least kernel 3.15 in the s390x KVM code,
>>> we can assume that the KVM_CAP_SYNC_REGS capability is always there.
>>> Thus turn this into a hard requirement now.
>>>
>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>> ---
>>>   target/s390x/kvm/kvm.c | 20 ++++++++++++++------
>>>   1 file changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
>>> index bc5c56a305..b3e2eaa2eb 100644
>>> --- a/target/s390x/kvm/kvm.c
>>> +++ b/target/s390x/kvm/kvm.c
>>> @@ -337,21 +337,29 @@ int kvm_arch_get_default_type(MachineState *ms)
>>>   int kvm_arch_init(MachineState *ms, KVMState *s)
>>>   {
>>> +    int required_caps[] = {
>>> +        KVM_CAP_DEVICE_CTRL,
>>> +        KVM_CAP_SYNC_REGS,
>>> +    };
>>> +
>>> +    for (int i = 0; i < ARRAY_SIZE(required_caps); i++) {
>>> +        if (!kvm_check_extension(s, required_caps[i])) {
>>> +            error_report("KVM is missing capability #%d - "
>>> +                         "please use kernel 3.15 or newer", required_caps[i]);
>>> +            return -1;
>>> +        }
>>> +    }
>>> +
>>>       object_class_foreach(ccw_machine_class_foreach, TYPE_S390_CCW_MACHINE,
>>>                            false, NULL);
>>> -    if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
>>> -        error_report("KVM is missing capability KVM_CAP_DEVICE_CTRL - "
>>> -                     "please use kernel 3.15 or newer");
>>> -        return -1;
>>> -    }
>>>       if (!kvm_check_extension(s, KVM_CAP_S390_COW)) {
>>>           error_report("KVM is missing capability KVM_CAP_S390_COW - "
>>>                        "unsupported environment");
>>>           return -1;
>>>       }
>>
>> Not sure if we also want to move KVM_CAP_S390_COW somehow. The message would be different.
> 
> IIRC that error could happen when you ran KVM within an older version of z/VM, so the "please use kernel 3.15 or newer" message would be completely misleading there.

Yes, thats what I was trying to say, we would need a different message.
Lets go with this patch.
> 
>> Aparch from that:
>> Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> 
> Thanks,
>    Thomas
> 
>