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

From: Vitaly Kuznetsov <[email-masked]>
Date: Mon, 23 Mar 2020 17:24:56 +0100

Sean Christopherson <[email-masked]> writes:

> 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.

Sounds cool! (not sure that with only two implementations people won't
call it 'over-engineered' but cool). My personal wish would just be that
function names in function implementations are not auto-generated so
e.g. a simple 'git grep vmx_hardware_setup' works but the way how we
fill vmx_x86_ops in can be macroed I guess.

-- 
Vitaly

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