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Subject: Re: [PATCH] KVM: nVMX: allow compiling with W=1
To:     =?UTF-8?Q?Valdis_Kl=c4=93tnieks?= <valdis.kletnieks@vt.edu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>
Cc:     x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <263441.1582858192@turing-police>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <96d8eb48-2961-8b85-9687-6bbc27e443a9@redhat.com>
Date:   Fri, 28 Feb 2020 10:36:10 +0100
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On 28/02/20 03:49, Valdis Klētnieks wrote:
> Compile error with CONFIG_KVM_INTEL=y and W=1:
> 
>   CC      arch/x86/kvm/vmx/vmx.o
> arch/x86/kvm/vmx/vmx.c:68:32: error: 'vmx_cpu_id' defined but not used [-Werror=unused-const-variable=]
>    68 | static const struct x86_cpu_id vmx_cpu_id[] = {
>       |                                ^~~~~~~~~~
> cc1: all warnings being treated as errors
> 
> When building with =y, the MODULE_DEVICE_TABLE macro doesn't generate a
> reference to the structure (or any code at all).  This makes W=1 compiles
> unhappy.
> 
> Wrap both in a #ifdef to avoid the issue.
> 
> Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 40a1467d1655..5c2fc2177b0d 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -65,11 +65,13 @@
>  MODULE_AUTHOR("Qumranet");
>  MODULE_LICENSE("GPL");
>  
> +#ifdef MODULE
>  static const struct x86_cpu_id vmx_cpu_id[] = {
>  	X86_FEATURE_MATCH(X86_FEATURE_VMX),
>  	{}
>  };
>  MODULE_DEVICE_TABLE(x86cpu, vmx_cpu_id);
> +#endif
>  
>  bool __read_mostly enable_vpid = 1;
>  module_param_named(vpid, enable_vpid, bool, 0444);
> 

Queued, and doing the same for AMD.

Paolo