Re: [PATCH] KVM: s390: Add new reset vcpu API

[Janosch Frank <frankja@linux.ibm.com>]

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On 11/29/19 3:33 PM, David Hildenbrand wrote:
> On 29.11.19 15:33, Janosch Frank wrote:
>> On 11/29/19 3:31 PM, David Hildenbrand wrote:
>>> On 29.11.19 15:21, Janosch Frank wrote:
>>>> The architecture states that we need to reset local IRQs for all CPU
>>>> resets. Because the old reset interface did not support the normal CPU
>>>> reset we never did that.
>>>>
>>>> Now that we have a new interface, let's properly clear out local IRQs
>>>> and let this commit be a reminder.
>>>>
>>>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>>>> ---
>>>>  arch/s390/kvm/kvm-s390.c | 25 ++++++++++++++++++++++++-
>>>>  include/uapi/linux/kvm.h |  7 +++++++
>>>>  2 files changed, 31 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>>> index d9e6bf3d54f0..2f74ff46b176 100644
>>>> --- a/arch/s390/kvm/kvm-s390.c
>>>> +++ b/arch/s390/kvm/kvm-s390.c
>>>> @@ -529,6 +529,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>>>>  	case KVM_CAP_S390_CMMA_MIGRATION:
>>>>  	case KVM_CAP_S390_AIS:
>>>>  	case KVM_CAP_S390_AIS_MIGRATION:
>>>> +	case KVM_CAP_S390_VCPU_RESETS:
>>>>  		r = 1;
>>>>  		break;
>>>>  	case KVM_CAP_S390_HPAGE_1M:
>>>> @@ -3293,6 +3294,25 @@ static int kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>>>>  	return 0;
>>>>  }
>>>>  
>>>> +static int kvm_arch_vcpu_ioctl_reset(struct kvm_vcpu *vcpu, unsigned long type)
>>>> +{
>>>> +	int rc = -EINVAL;
>>>> +
>>>> +	switch (type) {
>>>> +	case KVM_S390_VCPU_RESET_NORMAL:
>>>> +		rc = 0;
>>>> +		kvm_clear_async_pf_completion_queue(vcpu);
>>>> +		kvm_s390_clear_local_irqs(vcpu);
>>>> +		break;
>>>> +	case KVM_S390_VCPU_RESET_INITIAL:
>>>> +		/* fallthrough */
>>>> +	case KVM_S390_VCPU_RESET_CLEAR:
>>>> +		rc = kvm_arch_vcpu_ioctl_initial_reset(vcpu);
>>>
>>> As we now have two interfaces to achieve the same thing (initial reset),
>>> I do wonder if we should simply introduce
>>>
>>> KVM_S390_NORMAL_RESET
>>> KVM_S390_CLEAR_RESET
>>>
>>> instead ...
>>>
>>> Then you can do KVM_S390_NORMAL_RESET for the bugfix and
>>> KVM_S390_CLEAR_RESET later for PV.
>>>
>>> Does anything speak against that?
>>
>> Apart from loosing one more ioctl number probably not
> 
> Do we care? (I think not, but maybe I am missing something :) )
> 

I don't, maybe somebody else does
Btw. I'm struggling to find a good name for the capability:
KVM_CAP_S390_VCPU_ADDITIONAL_RESETS ?


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