Re: [PATCH v2 3/3] KVM: x86: use static calls to reduce kvm_x86_ops overhead

[Paolo Bonzini]

On 15/01/21 10:45, Peter Zijlstra wrote:
> On Thu, Jan 14, 2021 at 10:27:56PM -0500, Jason Baron wrote:
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 5060922..9d4492b 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1350,7 +1350,7 @@ void kvm_arch_free_vm(struct kvm *kvm);
> >   static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm)
> >   {
> >   	if (kvm_x86_ops.tlb_remote_flush &&
> > -	    !kvm_x86_ops.tlb_remote_flush(kvm))
> > +	    !static_call(kvm_x86_tlb_remote_flush)(kvm))
> >   		return 0;
> >   	else
> >   		return -ENOTSUPP;
>
> Would you be able to use something like this?
>
>    https://lkml.kernel.org/r/20201110101307.GO2651@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> we could also add __static_call_return1(), if that would help.

I think I'd rather make the default callee return -ENOTSUPP directly and 
remove the "if" completely.  So __static_call_return1() is not 
particularly useful here.

Paolo