Re: [PATCH v4 08/19] x86/resctrl: Introduce the interface to display monitor mode

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 6/13/24 20:40, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/24/24 5:23 AM, Babu Moger wrote:
>> The ABMC feature provides an option to the user to assign a hardware
>> counter to an RMID and monitor the bandwidth as long as it is assigned.
>> ABMC mode is enabled by default when supported. System can be one mode
>> at a time (Legacy monitor mode or ABMC mode).
>>
>> Provide an interface to display the monitor mode on the system.
>>      $cat /sys/fs/resctrl/info/L3_MON/mbm_assign
>>      [abmc]
>>      legacy
> 
> Output is different from cover letter and what this patch implements.

My bad. Will fix it,

> 
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>> v4: Fixed the checks for legacy and abmc mode. Default it ABMC.
>>
>> v3: New patch to display ABMC capability.
>> ---
>>   Documentation/arch/x86/resctrl.rst     | 10 ++++++++++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++++++++
>>   3 files changed, 34 insertions(+)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst
>> b/Documentation/arch/x86/resctrl.rst
>> index 7ab8172ef208..ab3cde61a124 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -261,6 +261,16 @@ with the following files:
>>       Available when ABMC feature is supported. The number of ABMC counters
>>       available for configuration.
>>   +"mbm_assign":
> 
> This name is not ideal but I am having trouble finding a better one ... I
> have
> seen you use "monitor mode" a couple of times (even in shortlog), so maybe
> that
> could be the start of a more generic name? "mbm_mode"?

mbm_mode sounds good. Like this.

$cat /sys/fs/resctrl/info/L3_MON/mbm_mode
[abmc]
legacy

Keeping just "legacy" vs mbm_legacy.


> 
>> +    Available when ABMC feature is supported. Reports the list of
>> assignable
> 
> Why not always make this file available? At least it will display that
> legacy mode is supported and it gives user space an always present file to
> query to
> determine support.

Ok. Sure.

> 
>> +    monitoring features supported. The enclosed brackets indicate which
>> +    feature is enabled.
>> +    ::
>> +
>> +      cat /sys/fs/resctrl/info/L3_MON/mbm_assign
>> +      [abmc]
>> +      mbm_legacy
>> +
>>   "max_threshold_occupancy":
>>           Read/write file provides the largest value (in
>>           bytes) at which a previously used LLC_occupancy
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c
>> b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index e75a6146068b..b1d002e5e93d 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1071,6 +1071,7 @@ int __init rdt_get_mon_l3_config(struct
>> rdt_resource *r)
>>             if (rdt_cpu_has(X86_FEATURE_ABMC)) {
>>               r->abmc_capable = true;
>> +            resctrl_file_fflags_init("mbm_assign", RFTYPE_MON_INFO);
>>               /*
>>                * Query CPUID_Fn80000020_EBX_x05 for number of
>>                * ABMC counters
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 9148d1234ede..3071bbb7a15e 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -856,6 +856,23 @@ static int rdtgroup_num_cntrs_show(struct
>> kernfs_open_file *of,
>>       return 0;
>>   }
>>   +static int rdtgroup_mbm_assign_show(struct kernfs_open_file *of,
>> +                    struct seq_file *s, void *v)
>> +{
>> +    struct rdt_resource *r = of->kn->parent->priv;
>> +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> 
> Please use arch helper to just get abmc state instead of fs code
> digging into arch structures.

Ok. I will use "resctrl_arch_get_abmc_enabled()" to get abmc state.

> 
>> +
>> +    if (hw_res->abmc_enabled) {
>> +        seq_puts(s, "[abmc]\n");
>> +        seq_puts(s, "mbm_legacy\n");
>> +    } else {
>> +        seq_puts(s, "abmc\n");
>> +        seq_puts(s, "[mbm_legacy]\n");
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   #ifdef CONFIG_PROC_CPU_RESCTRL
>>     /*
>> @@ -1913,6 +1930,12 @@ static struct rftype res_common_files[] = {
>>           .seq_show    = mbm_local_bytes_config_show,
>>           .write        = mbm_local_bytes_config_write,
>>       },
>> +    {
>> +        .name        = "mbm_assign",
>> +        .mode        = 0444,
>> +        .kf_ops        = &rdtgroup_kf_single_ops,
>> +        .seq_show    = rdtgroup_mbm_assign_show,
>> +    },
>>       {
>>           .name        = "cpus",
>>           .mode        = 0644,
> 
> Reinette
> 

-- 
Thanks
Babu Moger