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

[Xin Li <xin@xxxxxxxxx>]

On 1/22/2025 12:20 PM, Babu Moger wrote:
> 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);

This is the existing code, however it would be better to use wrmsrl()
when the higher 32-bit are all 0s:

	wrmsrl(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config);

Thanks!
    Xin