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

From: David Hildenbrand <david@redhat.com>
To: Janosch Frank <frankja@linux.ibm.com>, kvm@vger.kernel.org
Cc: thuth@redhat.com, borntraeger@de.ibm.com, mihajlov@linux.ibm.com,
	cohuck@redhat.com, linux-s390@vger.kernel.org
Subject: Re: [PATCH] KVM: s390: Add new reset vcpu API
Date: Fri, 29 Nov 2019 15:33:53 +0100	[thread overview]
Message-ID: <227a8fce-7e14-030e-b0a4-17e4521eed98@redhat.com> (raw)
In-Reply-To: <8e1aa1af-d929-e36b-f341-aa7dbe27f6a4@linux.ibm.com>

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 :) )

-- 
Thanks,

David / dhildenb