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

Moger, Babu
2025-04-15T15:01:01Z

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@amd.com>
>> ---
> ...
>
>> ---
>> 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