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Date:   Wed, 13 Jan 2021 09:17:22 -0800
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Jason Baron <jbaron@akamai.com>, kvm@vger.kernel.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        peterz@infradead.org, aarcange@redhat.com, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] KVM: x86: introduce definitions to support static
 calls for kvm_x86_ops
Message-ID: <X/8rIgrMkb61/la9@google.com>
References: <cover.1610379877.git.jbaron@akamai.com>
 <ce483ce4a1920a3c1c4e5deea11648d75f2a7b80.1610379877.git.jbaron@akamai.com>
 <ee071807-5ce5-60c1-c5df-b0b3e068b2ba@redhat.com>
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On Wed, Jan 13, 2021, Paolo Bonzini wrote:
> If you need to choose between DECLARE_STATIC_CALL_NULL and
> DECLARE_STATIC_CALL, you can have kvm-x86-ops.h use one of two macros
> KVM_X86_OP_NULL and KVM_X86_OP.
> 
> #define KVM_X86_OP(func) \
> 	DECLARE_STATIC_CALL(kvm_x86_##func,	\
> 			    *(((struct kvm_x86_ops *)0)->func));
> 
> #define KVM_X86_OP_NULL(func) \
> 	DECLARE_STATIC_CALL_NULL(kvm_x86_##func,	\

Gah, DECLARE_STATIC_CALL_NULL doesn't exist, though it's referenced in a comment.
I assume these should be s/DECLARE/DEFINE?  I haven't fully grokked the static
call code yet...

> 			    *(((struct kvm_x86_ops *)0)->func));
> 
> #include <asm/kvm-x86-ops.h>
> 
> ...
> 
> #define KVM_X86_OP(func) \
>   static_call_update(kvm_x86_##func, kvm_x86_ops.func)
> #define KVM_X86_OP_NULL(func) \
>   static_call_update(kvm_x86_##func, kvm_x86_ops.func)
> #include <asm/kvm-x86-ops.h>
> 
> In that case vmx.c and svm.c could define KVM_X86_OP_NULL to an empty string
> and list the optional callbacks manually.
> 
> Paolo
>