linux-kernel - Re: [PATCH] x86: kvm: hide the unused 'cpu' variable

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Date:   Wed, 4 Apr 2018 13:51:13 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: kvm: hide the unused 'cpu' variable

On 04.04.2018 12:44, Arnd Bergmann wrote:
> The local variable was newly introduced but is only accessed in one
> place on x86_64, but not on 32-bit:
> 
> arch/x86/kvm/vmx.c: In function 'vmx_save_host_state':
> arch/x86/kvm/vmx.c:2175:6: error: unused variable 'cpu' [-Werror=unused-variable]
> 
> This puts it into another #ifdef.
> 
> Fixes: 35060ed6a1ff ("x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/x86/kvm/vmx.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 8307f625ea99..7399a4a17f78 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2357,7 +2357,9 @@ static unsigned long segment_base(u16 selector)
>  static void vmx_save_host_state(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +#ifdef CONFIG_X86_64
>  	int cpu = raw_smp_processor_id();
> +#endif
>  	int i;
>  
>  	if (vmx->host_state.loaded)
> 

Can't we get rid of the variable and just do it inline?

Anyhow, fixes the problem

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 

Thanks,

David / dhildenb