Re: [PATCH 1/5] fs/resctrl: Drop support for different bandwidth delay mappings

[Chen Yu]

Hi Reinette,

On Thu, Sep 03, 2026 at 09:57:03AM -0700, Reinette Chatre wrote:
>  
> -/*
> - * Map the memory b/w percentage value to delay values
> - * that can be written to QOS_MSRs.
> - * There are currently no SKUs which support non linear delay values.
> - */
> -static u32 delay_bw_map(unsigned long bw, struct rdt_resource *r)
> -{
> -	if (r->membw.delay_linear)
> -		return MAX_MBA_BW - bw;
> -
> -	pr_warn_once("Non Linear delay-bw map not supported but queried\n");
> -	return MAX_MBA_BW;
> -}
> -
>  static void mba_wrmsr_intel(struct msr_param *m)
>  {
>  	struct rdt_hw_ctrl_domain *hw_dom = resctrl_to_arch_ctrl_dom(m->dom);
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(m->res);
>  	unsigned int i;
>  
> -	/*  Write the delay values for mba. */
> +	if (!m->res->membw.delay_linear) {
> +		pr_warn_once("Non-linear bandwidth delay not supported\n");
> +		return;

Previously if linear delay is not supported, we still write MAX_MBA_BW
to MSR, and here we return with MSR untouched, this should be the expected
behavior? Besides, in patch 2, __get_mem_config_intel() returns false for
non-linear-delay platform thus MB resource's alloc_capable is false,
do we still need to do the linear check in mba_wrmsr_intel() in patch 1
as the code path will not be triggered?

thanks,
Chenyu