Re: [PATCH v12 16/26] x86/resctrl: Report 'Unassigned' for MBM events in mbm_cntr_assign mode

[Moger, Babu]

Hi Reinette,

On 4/11/25 16:08, Reinette Chatre wrote:
> Hi Babu,
> 
> On 4/3/25 5:18 PM, Babu Moger wrote:
>> In mbm_cntr_assign mode, the hardware counter should be assigned to read
>> the MBM events.
>>
>> Report 'Unassigned' in case the user attempts to read the events without
> 
> "the events" -> "the event"?

Sure.

> 
>> assigning the counter.
> 
> "the counter" -> "a hardware counter"?
> 

Sure.

>>
>> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
>> ---
> ...
> 
>> ---
>>  Documentation/arch/x86/resctrl.rst        | 10 ++++++++++
>>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 14 ++++++++++++++
>>  arch/x86/kernel/cpu/resctrl/internal.h    |  3 +++
>>  arch/x86/kernel/cpu/resctrl/monitor.c     |  4 ++--
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    |  2 +-
>>  5 files changed, 30 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>> index 44128fbda4fe..71ed1cfed33a 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -430,6 +430,16 @@ When monitoring is enabled all MON groups will also contain:
>>  	for the L3 cache they occupy). These are named "mon_sub_L3_YY"
>>  	where "YY" is the node number.
>>  
>> +	The mbm_cntr_assign mode offers "num_mbm_cntrs" number of counters
>> +	and allows users to assign a counter to mon_hw_id, event pair enabling
>> +	bandwidth monitoring for as long as the counter remains assigned.
>> +	The hardware will continue tracking the assigned mon_hw_id until
>> +	the user manually unassigns it, ensuring that counters are not reset
>> +	during this period. System may run out of assignable counters when
>> +	all the counters are already assigned. In that case, MBM event counters
> 
> Counters could be unassigned even if there are assignable counters available.
> 
> I think the "System may run ..." sentence should be dropped.
> The "In that case ..." sentence could be simplified with something like:
> "An MBM event returns 'Unassigned' when the event does not have a hardware
> counter assigned."
> 

Sure.

>> +	will return 'Unassigned' when the event is read. Users must manually
>> +	assign a counter to read the events.
>> +
>>  "mon_hw_id":
>>  	Available only with debug option. The identifier used by hardware
>>  	for the monitor group. On x86 this is the RMID.
> 
> Reinette
> 
> 

-- 
Thanks
Babu Moger