linux-kernel - Re: [PATCH] KVM: SVM: hyper-v: placate modpost section mismatch error

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Date:   Wed, 22 Feb 2023 15:15:08 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: SVM: hyper-v: placate modpost section mismatch error

Randy Dunlap <rdunlap@...radead.org> writes:

> modpost reports section mismatch errors/warnings:
> WARNING: modpost: vmlinux.o: section mismatch in reference: svm_hv_hardware_setup (section: .text) -> (unknown) (section: .init.data)
> WARNING: modpost: vmlinux.o: section mismatch in reference: svm_hv_hardware_setup (section: .text) -> (unknown) (section: .init.data)
> WARNING: modpost: vmlinux.o: section mismatch in reference: svm_hv_hardware_setup (section: .text) -> (unknown) (section: .init.data)
>
> Marking svm_hv_hardware_setup() as __init fixes the warnings.
>
> I don't know why this should be needed -- it seems like a compiler
> problem to me since the calling function is marked as __init.
>
> This "(unknown) (section: .init.data)" all refer to svm_x86_ops.
>
> Fixes: 1e0c7d40758b ("KVM: SVM: hyper-v: Remote TLB flush for SVM")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Cc: Vineeth Pillai <viremana@...ux.microsoft.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: kvm@...r.kernel.org
> ---
>  arch/x86/kvm/svm/svm_onhyperv.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff -- a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
> --- a/arch/x86/kvm/svm/svm_onhyperv.h
> +++ b/arch/x86/kvm/svm/svm_onhyperv.h
> @@ -30,7 +30,7 @@ static inline void svm_hv_init_vmcb(stru
>  		hve->hv_enlightenments_control.msr_bitmap = 1;
>  }
>  
> -static inline void svm_hv_hardware_setup(void)
> +static inline __init void svm_hv_hardware_setup(void)
>  {
>  	if (npt_enabled &&
>  	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB) {
>

There's a second empty svm_hv_hardware_setup() implementation 50 lines
below in the same file for !if IS_ENABLED(CONFIG_HYPERV) case and I
think it needs to be marked as '__init' as well.

-- 
Vitaly