Re: [PATCH v11 10/23] x86/resctrl: Remove MSR reading of event configuration value

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

Hi Reinette,

On 2/5/2025 5:58 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 1/22/25 12:20 PM, Babu Moger wrote:
>> The event configuration is domain specific and initialized during domain
>> initialization. The values are stored in struct rdt_hw_mon_domain.
>>
>> It is not required to read the configuration register every time user asks
>> for it. Use the value stored in struct rdt_hw_mon_domain instead.
>>
>> Introduce resctrl_arch_mon_event_config_get() and
>> resctrl_arch_mon_event_config_set() to get/set architecture domain specific
>> mbm_total_cfg/mbm_local_cfg values.
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
> 
>> ---
>>   arch/x86/kernel/cpu/resctrl/internal.h | 15 +++++++
>>   arch/x86/kernel/cpu/resctrl/monitor.c  | 46 +++++++++++++++++++
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 61 +++++---------------------
>>   3 files changed, 72 insertions(+), 50 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index ab28b9340ee7..cfaea20145d0 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -605,6 +605,18 @@ union cpuid_0x10_x_edx {
>>   	unsigned int full;
>>   };
>>   
>> +/**
>> + * struct mon_config_info - Monitoring event configuratiin details
> 
> Same typo as previous version.

I am really sorry about this.

> 
>> + * @d:			Domain for the event
>> + * @evtid:		Event type
>> + * @mon_config:		Event configuration value
>> + */
>> +struct mon_config_info {
>> +	struct rdt_mon_domain *d;
>> +	enum resctrl_event_id evtid;
>> +	u32 mon_config;
>> +};
>> +
>>   void rdt_last_cmd_clear(void);
>>   void rdt_last_cmd_puts(const char *s);
>>   __printf(1, 2)
>> @@ -674,4 +686,7 @@ int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable);
>>   bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r);
>>   void arch_mbm_evt_config_init(struct rdt_hw_mon_domain *hw_dom);
>>   unsigned int mon_event_config_index_get(u32 evtid);
>> +void resctrl_arch_mon_event_config_set(void *info);
>> +u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
>> +				      enum resctrl_event_id eventid);
>>   #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 8917c7261680..6fe9e610e9a0 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1324,3 +1324,49 @@ int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
>>   
>>   	return 0;
>>   }
>> +
>> +u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
>> +				      enum resctrl_event_id eventid)
>> +{
>> +	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>> +
>> +	switch (eventid) {
>> +	case QOS_L3_OCCUP_EVENT_ID:
>> +		break;
>> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
>> +		return hw_dom->mbm_total_cfg;
>> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
>> +		return hw_dom->mbm_local_cfg;
>> +	}
>> +
>> +	/* Never expect to get here */
>> +	WARN_ON_ONCE(1);
>> +
>> +	return INVALID_CONFIG_VALUE;
>> +}
>> +
>> +void resctrl_arch_mon_event_config_set(void *info)
>> +{
>> +	struct mon_config_info *mon_info = info;
>> +	struct rdt_hw_mon_domain *hw_dom;
>> +	unsigned int index;
>> +
>> +	index = mon_event_config_index_get(mon_info->evtid);
>> +	if (index == INVALID_CONFIG_INDEX)
>> +		return;
>> +
>> +	wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
>> +
>> +	hw_dom = resctrl_to_arch_mon_dom(mon_info->d);
>> +
>> +	switch (mon_info->evtid) {
>> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
>> +		hw_dom->mbm_total_cfg = mon_info->mon_config;
>> +		break;
>> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
>> +		hw_dom->mbm_local_cfg = mon_info->mon_config;
>> +		break;
>> +	default:
>> +		break;
>> +	}
>> +}
> 
> This new arch API has sharp corners because of asymmetry of where resctrl
> runs the arch function. I do not think it is required to change this since we
> can only speculate about how this may be used in the future but I do think
> it will be helpful to add comments that highlight:
> 
> resctrl_arch_mon_event_config_get() ->  May run on CPU that does not belong to domain.
> resctrl_arch_mon_event_config_set() ->  Runs on CPU that belongs to domain.

Sure. will do.

> 
> ...
> 
>> @@ -1683,33 +1653,23 @@ static int mbm_local_bytes_config_show(struct kernfs_open_file *of,
>>   	return 0;
>>   }
>>   
>> -static void mon_event_config_write(void *info)
>> -{
>> -	struct mon_config_info *mon_info = info;
>> -	unsigned int index;
>> -
>> -	index = mon_event_config_index_get(mon_info->evtid);
>> -	if (index == INVALID_CONFIG_INDEX) {
>> -		pr_warn_once("Invalid event id %d\n", mon_info->evtid);
>> -		return;
>> -	}
>> -	wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
>> -}
>>   
>>   static void mbm_config_write_domain(struct rdt_resource *r,
>>   				    struct rdt_mon_domain *d, u32 evtid, u32 val)
>>   {
>>   	struct mon_config_info mon_info = {0};
> 
> As discussed in previous version it is unnecessary to explicitly initialize
> the structure if it is fully initialized in the code. This avoids need for
> future cleanups like commit 29eaa7958367 ("x86/resctrl: Slightly clean-up mbm_config_show()")

Yes. Need to change it.

thanks
Babu