linux-kernel - Re: [PATCH v2 3/3] KVM: x86: use static calls to reduce kvm_x86

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Date:   Fri, 15 Jan 2021 10:45:49 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jason Baron <jbaron@...mai.com>
Cc:     pbonzini@...hat.com, seanjc@...gle.com, kvm@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH v2 3/3] KVM: x86: use static calls to reduce kvm_x86_ops
 overhead

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@hirez.programming.kicks-ass.net

we could also add __static_call_return1(), if that would help.