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

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Date:   Mon, 15 Nov 2021 13:33:56 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...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
Subject: Re: [PATCH 0/5] KVM: Cap KVM_CAP_NR_VCPUS by KVM_CAP_MAX_VCPUS and
 re-purpose it on x86

Am 11.11.21 um 17:32 schrieb Paolo Bonzini:
> On 11/11/21 17:27, Vitaly Kuznetsov wrote:
>> This is a comtinuation of "KVM: x86: Drop arbitraty KVM_SOFT_MAX_VCPUS"
>> (https://lore.kernel.org/kvm/20211111134733.86601-1-vkuznets@redhat.com/)
>> work.
>>
>> 1) Enforce KVM_CAP_NR_VCPUS <= KVM_CAP_MAX_VCPUS rule on all
>>   architectures. [Sean Christopherson]
>> 2) Make KVM_CAP_NR_VCPUS return num_online_cpus() and not an arbitrary
>>   value of '710' on x86.
>>
>> Everything but x86 was only 'eyeball tested', the change is trivial
>> but sorry in advance if I screwed up)
> 
> Christian, can you look at this for s390?  Returning a fixed value seems wrong for KVM_CAP_NR_VCPUS.

If we talk about recommended number, then num_online_cpus() also seems to make sense on s390 so
if you change that for s390 as well I can ACK this.