Re: [RFC PATCH v3 08/17] x86/resctrl: Initialize assignable counters bitmap

Moger, Babu
2024-05-07T20:03:34Z

Hi Reinette,

On 5/3/24 18:31, Reinette Chatre wrote:
> Hi Babu,
>
> On 3/28/2024 6:06 PM, Babu Moger wrote:
>> AMD Hardware provides a set of counters when the ABMC feature is supported.
>> These counters are used for assigning events to the resctrl group.
>>
>> Introduce the bitmap assign_cntrs_free_map to allocate and free the
>> counters.
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>>
>> ---
>> v3: Changed the bitmap name to assign_cntrs_free_map. Removed abmc
>> from the name.
>>
>> v2: Changed the bitmap name to assignable_counter_free_map from
>> abmc_counter_free_map.
>> ---
>> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 +++++++++++++++++++
>> 1 file changed, 19 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index f49073c86884..2c7583e7b541 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -186,6 +186,22 @@ bool closid_allocated(unsigned int closid)
>> return !test_bit(closid, &closid_free_map);
>> }
>>
>> +static u64 assign_cntrs_free_map;
>> +static u32 assign_cntrs_free_map_len;
>
> Please provide summary in comments about what these globals are and how they
> are used.
>

Sure.

>> +
>> +static void assign_cntrs_init(void)
>> +{
>> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>> +
>> + if (r->mbm_assign_cntrs > 64) {
>> + r->mbm_assign_cntrs = 64;
>> + WARN(1, "Cannot support more than 64 Assignable counters\n");
>
> I am a bit confused here. The configuration registers are introduced in patch #10
> and if I counted right there are 5 bits for the counter id. It thus seems to me
> as though there needs to be some checking during enumeration time to ensure
> that all counters enumerated can be configured.

Ok. I will remove this check here and move it to enumeration time in
rdt_get_mon_l3_config.

>
>> + }
>> +
>> + assign_cntrs_free_map = BIT_MASK(r->mbm_assign_cntrs) - 1;
>
> Please use bitmap API. For example, bitmap_fill()

Ok. Sure.

>
>> + assign_cntrs_free_map_len = r->mbm_assign_cntrs;
>> +}
>> +
>> /**
>> * rdtgroup_mode_by_closid - Return mode of resource group with closid
>> * @closid: closid if the resource group
>> @@ -2459,6 +2475,9 @@ static int resctrl_abmc_setup(enum resctrl_res_level l, bool enable)
>> struct rdt_resource *r = &rdt_resources_all[l].r_resctrl;
>> struct rdt_domain *d;
>>
>> + /* Reset the counters bitmap */
>> + assign_cntrs_init();
>> +
>
> (At this point it is unclear when resctrl_abmc_setup() is called to understand
> if reset of bitmap may be appropriate. Please do expand all changelogs to help
> readers along with how this implementation is intended to work.)

resctrl_abmc_setup() is called either while enabling or disabling the ABMC
feature. In both these cases the bitmap assign_cntrs_free_map needs to be
reset.

Will add comments here,

>
>> /* Update QOS_CFG MSR on all the CPUs in cpu_mask */
>> list_for_each_entry(d, &r->domains, list) {
>> on_each_cpu_mask(&d->cpu_mask, resctrl_abmc_msrwrite, &enable, 1);
>
> Reinette
>

--
Thanks
Babu Moger