linux-kernel - Re: [PATCH -next] x86: Fix unused variable 'hi'

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Date:   Tue, 23 Mar 2021 11:32:50 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Xu Yihang <xuyihang@...wei.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        johnny.chenyi@...wei.com
Subject: Re: [PATCH -next] x86: Fix unused variable 'hi'

On Tue, Mar 23, 2021 at 10:50:13AM +0800, Xu Yihang wrote:
> Fixes the following W=1 kernel build warning(s):
> arch/x86/hyperv/hv_apic.c:58:15: warning: variable ‘hi’ set but not used [-Wunused-but-set-variable]
> 
> Compiled with CONFIG_HYPERV enabled:
> make allmodconfig ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
> make W=1 arch/x86/hyperv/hv_apic.o ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
> 
> HV_X64_MSR_EOI stores on bit 31:0 and HV_X64_MSR_TPR stores in bit 7:0, which means higher
> 32 bits are not really used, therefore  potentially cast to void in order to silent this warning.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Xu Yihang <xuyihang@...wei.com>
> ---
>  arch/x86/hyperv/hv_apic.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index 284e73661a18..a8b639498033 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -60,9 +60,11 @@ static u32 hv_apic_read(u32 reg)
>  	switch (reg) {
>  	case APIC_EOI:
>  		rdmsr(HV_X64_MSR_EOI, reg_val, hi);
> +		(void) hi;
>  		return reg_val;
>  	case APIC_TASKPRI:
>  		rdmsr(HV_X64_MSR_TPR, reg_val, hi);
> +		(void) hi;

I would like to remove the space while committing this patch. There is
no need for you to do anything.

Wei.

>  		return reg_val;
>  
>  	default:
> -- 
> 2.17.1
>