linux-kernel - Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX

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Date:   Tue, 16 Nov 2021 09:15:43 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Eduardo Habkost <ehabkost@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Andrew Jones <drjones@...hat.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Anup Patel <anup.patel@....com>,
        Paul Mackerras <paulus@...abs.org>,
        Michael Ellerman <mpe@...erman.id.au>, kvm-ppc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>
Subject: Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS and
 re-purpose it on x86



Am 15.11.21 um 17:04 schrieb Vitaly Kuznetsov:
[...]
> or cap KVM_CAP_MAX_VCPUS value with num_online_cpus(), e.g.
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 6a6dd5e1daf6..1cfe36f6432e 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -585,6 +585,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>                          r = KVM_MAX_VCPUS;
>                  else if (sclp.has_esca && sclp.has_64bscao)
>                          r = KVM_S390_ESCA_CPU_SLOTS;
> +               if (ext == KVM_CAP_NR_VCPUS)
> +                       r = min_t(unsigned int, num_online_cpus(), r);
>                  break;
>          case KVM_CAP_S390_COW:
>                  r = MACHINE_HAS_ESOP;

Acked-by: Christian Borntraeger <borntraeger@...ibm.com>


I think this is the better variant. Thanks.