linux-kernel - Re: [PATCH 5/5] KVM: x86: Set kvm_x86_ops only after ->hardware

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Message-ID: <20200131185531.GB18946@linux.intel.com>
Date:   Fri, 31 Jan 2020 10:55:32 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] KVM: x86: Set kvm_x86_ops only after
 ->hardware_setup() completes

On Thu, Jan 30, 2020 at 06:44:09AM +0100, Paolo Bonzini wrote:
> On 30/01/20 01:10, Sean Christopherson wrote:
> > Set kvm_x86_ops with the vendor's ops only after ->hardware_setup()
> > completes to "prevent" using kvm_x86_ops before they are ready, i.e. to
> > generate a null pointer fault instead of silently consuming unconfigured
> > state.
> 
> What about even copying kvm_x86_ops by value, so that they can be
> accessed with "kvm_x86_ops.callback()" and save one memory access?

Oooh, I like that idea.  And {svm,vmx}_x86_ops could be marked __initdata
to save a few bytes and force all the runtime stuff through kvm_x86_ops.