Re: [PATCH RFC 6/6] KVM: s390: generalize kvm_s390_get_tod_clock_ext()

[Cornelia Huck <cohuck@xxxxxxxxxx>]

On Wed,  7 Feb 2018 12:46:47 +0100
David Hildenbrand <david@xxxxxxxxxx> wrote:

> Move the Multiple-epoch facility handling into it and rename it to
> kvm_s390_get_tod_clock().
> 
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>  arch/s390/kvm/kvm-s390.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)

Looks correct, but I'm not sure what this buys us?

> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 0c0eed7d60a8..df452b8b4f26 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -990,8 +990,8 @@ static int kvm_s390_set_tod(struct kvm *kvm, struct kvm_device_attr *attr)
>  	return ret;
>  }
>  
> -static void kvm_s390_get_tod_clock_ext(struct kvm *kvm,
> -					struct kvm_s390_vm_tod_clock *gtod)
> +static void kvm_s390_get_tod_clock(struct kvm *kvm,
> +				   struct kvm_s390_vm_tod_clock *gtod)
>  {
>  	struct kvm_s390_tod_clock_ext htod;
>  
> @@ -1000,10 +1000,12 @@ static void kvm_s390_get_tod_clock_ext(struct kvm *kvm,
>  	get_tod_clock_ext((char *)&htod);
>  
>  	gtod->tod = htod.tod + kvm->arch.epoch;
> -	gtod->epoch_idx = htod.epoch_idx + kvm->arch.epdx;
> -
> -	if (gtod->tod < htod.tod)
> -		gtod->epoch_idx += 1;
> +	gtod->epoch_idx = 0;
> +	if (test_kvm_facility(kvm, 139)) {
> +		gtod->epoch_idx = htod.epoch_idx + kvm->arch.epdx;
> +		if (gtod->tod < htod.tod)
> +			gtod->epoch_idx += 1;
> +	}
>  
>  	preempt_enable();
>  }
> @@ -1012,13 +1014,7 @@ static int kvm_s390_get_tod_ext(struct kvm *kvm, struct kvm_device_attr *attr)
>  {
>  	struct kvm_s390_vm_tod_clock gtod;
>  
> -	memset(&gtod, 0, sizeof(gtod));
> -
> -	if (test_kvm_facility(kvm, 139))
> -		kvm_s390_get_tod_clock_ext(kvm, &gtod);
> -	else
> -		gtod.tod = kvm_s390_get_tod_clock_fast(kvm);
> -
> +	kvm_s390_get_tod_clock(kvm, &gtod);
>  	if (copy_to_user((void __user *)attr->addr, &gtod, sizeof(gtod)))
>  		return -EFAULT;
>