linux-kernel - Re: [PATCH v2 1/9] KVM: x86: check validity of argument to KVM_SET_MP

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Date:   Tue, 16 Aug 2022 22:50:10 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, vkuznets@...hat.com
Subject: Re: [PATCH v2 1/9] KVM: x86: check validity of argument to
 KVM_SET_MP_STATE

On Mon, Aug 15, 2022, Maxim Levitsky wrote:
> On Thu, 2022-08-11 at 17:05 -0400, Paolo Bonzini wrote:
> > An invalid argument to KVM_SET_MP_STATE has no effect other than making the
> > vCPU fail to run at the next KVM_RUN.  Since it is extremely unlikely that
> > any userspace is relying on it, fail with -EINVAL just like for other
> > architectures.
> > 
> > Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> > ---
> >  arch/x86/kvm/x86.c | 20 +++++++++++++++++---
> >  1 file changed, 17 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 132d662d9713..c44348bb6ef2 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -10653,7 +10653,8 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
> >         case KVM_MP_STATE_INIT_RECEIVED:
> >                 break;
> >         default:
> > -               return -EINTR;
> > +               WARN_ON(1);
> 
> Very small nitpick: Maybe WARN_ON_ONCE after all? 

+1, I don't think warning multiple times would help triage/debug, and this seems
like something that will fire a lot if it fires at all.