linux-kernel - Re: [PATCH] x86/resctrl: Fix a silly -Wunused-but-set-variable warning

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Message-ID: <8537e27a-b565-2618-43d0-b70a1a4390e4@amd.com>
Date:   Tue, 24 Jan 2023 12:44:07 -0600
From:   "Moger, Babu" <babu.moger@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     kernel test robot <lkp@...el.com>, llvm@...ts.linux.dev,
        oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        x86@...nel.org, Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [PATCH] x86/resctrl: Fix a silly -Wunused-but-set-variable
 warning

Boris, Thanks for the fix.

Tested-by: Babu Moger <babu.moger@....com>


On 1/24/23 12:13, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@...en8.de>
>
> clang correctly complains
>
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c:1456:6: warning: variable \
>      'h' set but not used [-Wunused-but-set-variable]
>           u32 h;
>               ^
>
> but it can't know whether this use is innocuous or really a problem.
> There's a reason why those warning switches are behind a W=1 and not
> enabled by default - yes, one needs to do:
>
>   make W=1 CC=clang HOSTCC=clang arch/x86/kernel/cpu/resctrl/
>
> with clang 14 in order to trigger it.
>
> I would normally not take a silly fix like that but this one is simple
> and doesn't make the code uglier so...
>
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
> Link: https://lore.kernel.org/r/202301242015.kbzkVteJ-lkp@intel.com
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 5990589f8a21..e2c1599d1b37 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1453,17 +1453,17 @@ static void mon_event_config_read(void *info)
>  {
>  	struct mon_config_info *mon_info = info;
>  	unsigned int index;
> -	u32 h;
> +	u64 msrval;
>  
>  	index = mon_event_config_index_get(mon_info->evtid);
>  	if (index == INVALID_CONFIG_INDEX) {
>  		pr_warn_once("Invalid event id %d\n", mon_info->evtid);
>  		return;
>  	}
> -	rdmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, h);
> +	rdmsrl(MSR_IA32_EVT_CFG_BASE + index, msrval);
>  
>  	/* Report only the valid event configuration bits */
> -	mon_info->mon_config &= MAX_EVT_CONFIG_BITS;
> +	mon_info->mon_config = msrval & MAX_EVT_CONFIG_BITS;
>  }
>  
>  static void mondata_config_read(struct rdt_domain *d, struct mon_config_info *mon_info)

-- 
Thanks
Babu Moger