[v1] x86/resctrl: Fix a silly -Wunused-but-set-variable warning

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

Posted by Borislav Petkov 3 years ago

From: "Borislav Petkov (AMD)" <bp@alien8.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@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.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)
-- 
2.35.1

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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

Posted by Moger, Babu 3 years ago

Boris, Thanks for the fix.

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


On 1/24/23 12:13, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.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@intel.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.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

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

Posted by Reinette Chatre 3 years ago

Hi Boris,

On 1/24/2023 10:13 AM, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.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@intel.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Link: https://lore.kernel.org/r/202301242015.kbzkVteJ-lkp@intel.com
> ---

Thank you very much.

Acked-by: Reinette Chatre <reinette.chatre@intel.com>

Reinette