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

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Date:   Wed, 22 Feb 2023 08:18:40 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     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



On 2/22/23 06:15, Vitaly Kuznetsov wrote:
> 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.
> 

I saw that. I can make that change also. I was optimistic that since it is
empty, gcc would not be fooled by it.

v2 later today.

thanks.
-- 
~Randy