linux-kernel - Re: [PATCH RFC] KVM: x86: Drop arbitraty KVM_SOFT_MAX

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YY0qgUqM3CuDHWgB@google.com>
Date:   Thu, 11 Nov 2021 14:36:49 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Eduardo Habkost <ehabkost@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] KVM: x86: Drop arbitraty KVM_SOFT_MAX_VCPUS

On Thu, Nov 11, 2021, Paolo Bonzini wrote:
> On 11/11/21 14:47, Vitaly Kuznetsov wrote:
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index ac83d873d65b..91ef1b872b90 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -4137,7 +4137,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >   		r = !static_call(kvm_x86_cpu_has_accelerated_tpr)();
> >   		break;
> >   	case KVM_CAP_NR_VCPUS:
> > -		r = KVM_SOFT_MAX_VCPUS;
> > +		r = num_online_cpus();

I doubt it matters much in practice, but this really should be

		r = min(num_online_cpus(), KVM_MAX_VCPUS);

> >   		break;
> >   	case KVM_CAP_MAX_VCPUS:
> >   		r = KVM_MAX_VCPUS;
> > 
>