Re: [PATCH v2 2/5] x86,fs/resctrl: Remove unnecessary non-linear MBA configuration check

[Chen Yu]

On Wed, Oct 07, 2026 at 02:06:44PM -0700, Reinette Chatre wrote:
> Writing a bandwidth value from user space is rejected if the MBA resource
> has non-linear delay values while the architecture indicates (via
> resctrl_membw::arch_needs_linear) it can only configure resources with
> linear delay values. Intel indicates this for MBA while AMD and MPAM do not.
> 
> This check can never fail. No Intel SKU supports non-linear delay values,
> and the placeholder for such support, rdt_get_mb_table(), is only called
> during enumeration and always fails. A non-linear Intel MBA resource is
> thus never marked as capable of allocation, and resctrl never exposes it
> to user space or attempts to configure it. Every Intel MBA resource capable
> of allocation has linear delay values, and AMD and MPAM never indicate a
> need for them.
> 
> Fail enumeration of a non-linear Intel MBA resource directly to make clear
> that it is not supported, and remove the check together with the
> resctrl_membw::arch_needs_linear property it relies on.
> 
> Keep the informational message printed when such a system is encountered.
> While moving it, reword it to no longer refer to the removed mapping table,
> add the missing newline, and label the printed family value "family" instead
> of "cpu".
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
>

Reviewed-by: Chen Yu <yu.c.chen@xxxxxxxxx>

thanks,
Chenyu