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Subject: Re: [PATCH v2 2/2] s390:kvm: Topology expose TOPOLOGY facility
To:     Pierre Morel <pmorel@linux.ibm.com>, kvm@vger.kernel.org
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        frankja@linux.ibm.com, cohuck@redhat.com, david@redhat.com,
        thuth@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com,
        gor@linux.ibm.com
References: <1626973353-17446-1-git-send-email-pmorel@linux.ibm.com>
 <1626973353-17446-3-git-send-email-pmorel@linux.ibm.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <7163cf4a-479a-3121-2261-cfb6e4024d0c@de.ibm.com>
Date:   Fri, 23 Jul 2021 10:14:51 +0200
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On 22.07.21 19:02, Pierre Morel wrote:
> We add a KVM extension KVM_CAP_S390_CPU_TOPOLOGY to tell the
> userland hypervisor it is safe to activate the CPU Topology facility.

I think the old variant of using the CPU model was actually better.
It was just the patch description that was wrong.
  
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>   arch/s390/kvm/kvm-s390.c | 1 +
>   include/uapi/linux/kvm.h | 1 +
>   2 files changed, 2 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b655a7d82bf0..8c695ee79612 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -568,6 +568,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   	case KVM_CAP_S390_VCPU_RESETS:
>   	case KVM_CAP_SET_GUEST_DEBUG:
>   	case KVM_CAP_S390_DIAG318:
> +	case KVM_CAP_S390_CPU_TOPOLOGY:
>   		r = 1;
>   		break;
>   	case KVM_CAP_SET_GUEST_DEBUG2:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index d9e4aabcb31a..081ce0cd44b9 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1112,6 +1112,7 @@ struct kvm_ppc_resize_hpt {
>   #define KVM_CAP_BINARY_STATS_FD 203
>   #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
>   #define KVM_CAP_ARM_MTE 205
> +#define KVM_CAP_S390_CPU_TOPOLOGY 206
>   
>   #ifdef KVM_CAP_IRQ_ROUTING
>   
>