linux-kernel - Re: [PATCH v2 5/8] KVM: x86: Add WARNs to detect out-of-bounds register indices

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Message-ID: <20191009163600.GA19952@linux.intel.com>
Date:   Wed, 9 Oct 2019 09:36:00 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Reto Buerki <reet@...elabs.ch>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v2 5/8] KVM: x86: Add WARNs to detect out-of-bounds
 register indices

On Wed, Oct 09, 2019 at 12:50:44PM +0200, Paolo Bonzini wrote:
> On 27/09/19 23:45, Sean Christopherson wrote:
> > Open code the RIP and RSP accessors so as to avoid pointless overhead of
> > WARN_ON_ONCE().
> 
> Is there actually an overhead here?  It is effectively WARN_ON_ONCE(0)
> which should be compiled out just fine.

Doh, you're correct, it does get compiled out.