Re: [PATCH v2] KVM: s390: Add new reset vcpu API

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

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On 12/4/19 10:32 AM, Thomas Huth wrote:
> On 03/12/2019 17.20, 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 | 13 +++++++++++++
>>  include/uapi/linux/kvm.h |  4 ++++
>>  2 files changed, 17 insertions(+)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index d9e6bf3d54f0..602214c5616c 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:
>> @@ -3287,6 +3288,13 @@ static int kvm_arch_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu,
>>  	return r;
>>  }
>>  
>> +static int kvm_arch_vcpu_ioctl_normal_reset(struct kvm_vcpu *vcpu)
>> +{
>> +	kvm_clear_async_pf_completion_queue(vcpu);
>> +	kvm_s390_clear_local_irqs(vcpu);
>> +	return 0;
>> +}
>> +
>>  static int kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>>  {
>>  	kvm_s390_vcpu_initial_reset(vcpu);
>> @@ -4363,7 +4371,12 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>>  		r = kvm_arch_vcpu_ioctl_set_initial_psw(vcpu, psw);
>>  		break;
>>  	}
>> +	case KVM_S390_NORMAL_RESET:
>> +		r = kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>> +		break;
>>  	case KVM_S390_INITIAL_RESET:
>> +		/* fallthrough */
>> +	case KVM_S390_CLEAR_RESET:
>>  		r = kvm_arch_vcpu_ioctl_initial_reset(vcpu);
>>  		break;
> 
> Isn't clear reset supposed to do more than the initial reset? If so, I'd
> rather expect it the other way round:

In the PV patch I remove the fallthrough and add a function for the
clear reset. I add the UV reset calls into the
kvm_arch_vcpu_ioctl_*_reset() functions, therefore I can't fallthrough
because the Ultravisor does currently not allow staged resets (i.e.
first initial then clear if a clear reset is needed)

> 
> 	case KVM_S390_CLEAR_RESET:
> 		/* fallthrough */
> 	case KVM_S390_INITIAL_RESET:
> 		r = kvm_arch_vcpu_ioctl_initial_reset(vcpu);
> 		break;
> 
> ... so you can later add the additional stuff before the "/* fallthrough
> */"?
> 
>  Thomas
> 



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