[PATCH] x86/resctrl: Fix 'uninitialized symbol' build warning

[PATCH] x86/resctrl: Fix 'uninitialized symbol' build warning

[Babu Moger]

The recent commit 064855a69003 ("x86/resctrl: Fix default monitoring
groups reporting"), caused a RHEL8.5 build failure with an uninitialized
variable warning treated as an error. The commit removed the default case
snippet. The RHEL8.5 Makefile uses '-Werror=maybe-uninitialized' to force
uninitialized variable warnings to be treated as errors. This is also
reported by kernel test robot. The error from the RHEL8.5 build is below:

arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
  m->chunks += chunks;
            ^~

The upstream Makefile does not build using '-Werror=maybe-uninitialized'.
So, the problem is not seen there. Fix the problem by putting back the
default case snippet.

Fixes: 064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")
Cc: stable@vger.kernel.org
Reported-by: Terry Bowman <Terry.Bowman@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/6118d218.4ZZRXYKZCzQSq1Km%25lkp@intel.com/

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
 arch/x86/kernel/cpu/resctrl/monitor.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 57e4bb695ff9..8caf871b796f 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -304,6 +304,12 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
 	case QOS_L3_MBM_LOCAL_EVENT_ID:
 		m = &rr->d->mbm_local[rmid];
 		break;
+	default:
+		/*
+		 * Code would never reach here because an invalid
+		 * event id would fail the __rmid_read.
+		 */
+		return RMID_VAL_ERROR;
 	}
 
 	if (rr->first) {

Re: [PATCH] x86/resctrl: Fix 'uninitialized symbol' build warning

[Reinette Chatre]

On 8/20/2021 9:33 AM, Babu Moger wrote:
> The recent commit 064855a69003 ("x86/resctrl: Fix default monitoring
> groups reporting"), caused a RHEL8.5 build failure with an uninitialized
> variable warning treated as an error. The commit removed the default case
> snippet. The RHEL8.5 Makefile uses '-Werror=maybe-uninitialized' to force
> uninitialized variable warnings to be treated as errors. This is also
> reported by kernel test robot. The error from the RHEL8.5 build is below:
> 
> arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
> arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>    m->chunks += chunks;
>              ^~
> 
> The upstream Makefile does not build using '-Werror=maybe-uninitialized'.
> So, the problem is not seen there. Fix the problem by putting back the
> default case snippet.
> 
> Fixes: 064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")
> Cc: stable@vger.kernel.org
> Reported-by: Terry Bowman <Terry.Bowman@amd.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/6118d218.4ZZRXYKZCzQSq1Km%25lkp@intel.com/
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>   arch/x86/kernel/cpu/resctrl/monitor.c |    6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 57e4bb695ff9..8caf871b796f 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -304,6 +304,12 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
>   	case QOS_L3_MBM_LOCAL_EVENT_ID:
>   		m = &rr->d->mbm_local[rmid];
>   		break;
> +	default:
> +		/*
> +		 * Code would never reach here because an invalid
> +		 * event id would fail the __rmid_read.
> +		 */
> +		return RMID_VAL_ERROR;
>   	}
>   
>   	if (rr->first) {
> 

Thank you very much Babu.

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

Reinette

Re: [PATCH] x86/resctrl: Fix 'uninitialized symbol' build warning

[Wei Huang]

On 8/20/21 11:33 AM, Babu Moger wrote:
> The recent commit 064855a69003 ("x86/resctrl: Fix default monitoring
> groups reporting"), caused a RHEL8.5 build failure with an uninitialized

Don't mention RHEL in the commit message, just use "commercial Linux
distro".

> variable warning treated as an error. The commit removed the default case
> snippet. The RHEL8.5 Makefile uses '-Werror=maybe-uninitialized' to force

Ditto

> uninitialized variable warnings to be treated as errors. This is also
> reported by kernel test robot. The error from the RHEL8.5 build is below:
> 
> arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
> arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>   m->chunks += chunks;
>             ^~
> 
> The upstream Makefile does not build using '-Werror=maybe-uninitialized'.
> So, the problem is not seen there. Fix the problem by putting back the
> default case snippet.
> 
> Fixes: 064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")
> Cc: stable@vger.kernel.org
> Reported-by: Terry Bowman <Terry.Bowman@amd.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/6118d218.4ZZRXYKZCzQSq1Km%25lkp@intel.com/
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>  arch/x86/kernel/cpu/resctrl/monitor.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 57e4bb695ff9..8caf871b796f 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -304,6 +304,12 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
>  	case QOS_L3_MBM_LOCAL_EVENT_ID:
>  		m = &rr->d->mbm_local[rmid];
>  		break;
> +	default:
> +		/*
> +		 * Code would never reach here because an invalid
> +		 * event id would fail the __rmid_read.
> +		 */
> +		return RMID_VAL_ERROR;
>  	}

It used to return -EINVAL, you might want to do the same?

>  
>  	if (rr->first) {
> 

Re: [PATCH] x86/resctrl: Fix 'uninitialized symbol' build warning

[Babu Moger]

On 8/20/21 11:40 AM, Wei Huang wrote:
> 
> 
> On 8/20/21 11:33 AM, Babu Moger wrote:
>> The recent commit 064855a69003 ("x86/resctrl: Fix default monitoring
>> groups reporting"), caused a RHEL8.5 build failure with an uninitialized
> 
> Don't mention RHEL in the commit message, just use "commercial Linux
> distro".

Talked to Wei on this. I will replace RHEL8.5 with just RHEL.
> 
>> variable warning treated as an error. The commit removed the default case
>> snippet. The RHEL8.5 Makefile uses '-Werror=maybe-uninitialized' to force
> 
> Ditto

Same as above.

> 
>> uninitialized variable warnings to be treated as errors. This is also
>> reported by kernel test robot. The error from the RHEL8.5 build is below:
>>
>> arch/x86/kernel/cpu/resctrl/monitor.c: In function ‘__mon_event_count’:
>> arch/x86/kernel/cpu/resctrl/monitor.c:261:12: error: ‘m’ may be used
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>   m->chunks += chunks;
>>             ^~
>>
>> The upstream Makefile does not build using '-Werror=maybe-uninitialized'.
>> So, the problem is not seen there. Fix the problem by putting back the
>> default case snippet.
>>
>> Fixes: 064855a69003 ("x86/resctrl: Fix default monitoring groups reporting")
>> Cc: stable@vger.kernel.org
>> Reported-by: Terry Bowman <Terry.Bowman@amd.com>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Link: https://lore.kernel.org/lkml/6118d218.4ZZRXYKZCzQSq1Km%25lkp@intel.com/
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>>  arch/x86/kernel/cpu/resctrl/monitor.c |    6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 57e4bb695ff9..8caf871b796f 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -304,6 +304,12 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
>>  	case QOS_L3_MBM_LOCAL_EVENT_ID:
>>  		m = &rr->d->mbm_local[rmid];
>>  		break;
>> +	default:
>> +		/*
>> +		 * Code would never reach here because an invalid
>> +		 * event id would fail the __rmid_read.
>> +		 */
>> +		return RMID_VAL_ERROR;
>>  	}
> 
> It used to return -EINVAL, you might want to do the same?

No. The function prototype has changed a bit. We have to return
RMID_VAL_ERROR(u64).
Thanks
Babu
> 
>>  
>>  	if (rr->first) {
>>