Re: [PATCH v11 04/23] x86/resctrl: Apply Intel MBM quirk from rdt_get_l3_mon_config()

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Tony,

On 8/31/26 10:44 AM, Tony Luck wrote:

> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 0c2aa20148a1..0bce199a5f7b 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c

...

> @@ -421,6 +423,20 @@ static __init int snc_get_config(void)
>  	return ret;
>  }
>  
> +static void __init intel_rdt_mbm_apply_quirk(u32 num_rmid)
> +{
> +	int cf_index;
> +
> +	cf_index = num_rmid / 8 - 1;

I suspect that cf_index was made an "int" because the original code 
initialized it from int boot_cpu_data.x86_cache_max_rmid. Now that
cf_index is initialized from an unsigned, compared to size_t, and
used as array index ... unsigned looks more appropriate?

> +	if (cf_index >= ARRAY_SIZE(mbm_cf_table)) {
> +		pr_info("No MBM correction factor available\n");
> +		return;
> +	}
> +
> +	mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
> +	mbm_cf = mbm_cf_table[cf_index].cf;
> +}
> +
>  int __init rdt_get_l3_mon_config(struct rdt_resource *r)
>  {
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> @@ -500,25 +516,14 @@ int __init rdt_get_l3_mon_config(struct rdt_resource *r)
>  		hw_res->mbm_cntr_assign_enabled = true;
>  	}
>  
> +	if (intel_rdt_mbm_need_quirk)
> +		intel_rdt_mbm_apply_quirk(r->mon.num_rmid);
> +
>  	r->mon_capable = true;
>  
>  	return 0;
>  }
>  
> -void __init intel_rdt_mbm_apply_quirk(void)
> -{
> -	int cf_index;
> -
> -	cf_index = (boot_cpu_data.x86_cache_max_rmid + 1) / 8 - 1;
> -	if (cf_index >= ARRAY_SIZE(mbm_cf_table)) {
> -		pr_info("No MBM correction factor available\n");
> -		return;
> -	}
> -
> -	mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
> -	mbm_cf = mbm_cf_table[cf_index].cf;
> -}
> -
>  static void resctrl_abmc_set_one_amd(void *arg)
>  {
>  	bool *enable = arg;

Reinette