Subject: Re: [PATCH v3 2/9] KVM: x86: Move init-only kvm_x86_ops to separate struct

From: Sean Christopherson <[email-masked]>
Date: Mon, 23 Mar 2020 08:29:09 -0700

On Mon, Mar 23, 2020 at 01:10:40PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <[email-masked]> writes:
> 
> > +
> > +	.runtime_ops = &svm_x86_ops,
> > +};
> 
> Unrelated to your patch but I think we can make the naming of some of
> these functions more consistend on SVM/VMX, in particular I'd suggest 
> 
> has_svm() -> cpu_has_svm_support()
> is_disabled -> svm_disabled_by_bios()
> ...
> (see below for VMX)
> 
> > +
> >  static int __init svm_init(void)
> >  {
> > -	return kvm_init(&svm_x86_ops, sizeof(struct vcpu_svm),
> > +	return kvm_init(&svm_init_ops, sizeof(struct vcpu_svm),
> >  			__alignof__(struct vcpu_svm), THIS_MODULE);
> >  }
> >  
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 07299a957d4a..ffcdcc86f5b7 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7842,11 +7842,8 @@ static bool vmx_check_apicv_inhibit_reasons(ulong bit)
> >  }
> >  
> >  static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> > -	.cpu_has_kvm_support = cpu_has_kvm_support,
> > -	.disabled_by_bios = vmx_disabled_by_bios,
> > -	.hardware_setup = hardware_setup,
> >  	.hardware_unsetup = hardware_unsetup,
> > -	.check_processor_compatibility = vmx_check_processor_compat,
> > +
> >  	.hardware_enable = hardware_enable,
> >  	.hardware_disable = hardware_disable,
> >  	.cpu_has_accelerated_tpr = report_flexpriority,
> > @@ -7981,6 +7978,15 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> >  	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
> >  };
> >  
> > +static struct kvm_x86_init_ops vmx_init_ops __initdata = {
> > +	.cpu_has_kvm_support = cpu_has_kvm_support,
> > +	.disabled_by_bios = vmx_disabled_by_bios,
> > +	.check_processor_compatibility = vmx_check_processor_compat,
> > +	.hardware_setup = hardware_setup,
> 
> cpu_has_kvm_support() -> cpu_has_vmx_support()
> hardware_setup() -> vmx_hardware_setup()

Preaching to the choir on this one.  The VMX functions without prefixes in
in particular annoy me to no end, e.g. hardware_setup().  Though the worst
is probably ".vcpu_create = vmx_create_vcpu", if I had a nickel for every
time I've tried to find vmx_vcpu_create()...

What if we added a macro to auto-generate the common/required hooks?  E.g.:

  static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
	MANDATORY_KVM_X86_OPS(vmx),

	.pmu_ops = &intel_pmu_ops,

	...
  };

That'd enforce consistent naming, and would provide a bit of documentation
as to which hooks are optional, e.g. many of the nested hooks, and which
must be defined for KVM to function.

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