Re: [PATCH v6 2/3] arm_mpam: resctrl: Add pass-through resctrl_arch_preconvert_bw()

[Gavin Shan]

On 9/12/26 2:36 AM, Ben Horgan wrote:
> resctrl rounds up the percentage value of the MBA based on the bw_gran. As
> MPAM uses a binary fixed point fraction format for MBA rather than a
> decimal percentage, this introduces rounding errors.
>
> Without this additional rounding, if the user reads the value in an MB
> schema and then writes it back to the schema, the value in hardware won't
> change. However, with this additional rounding, this guarantee is broken
> for systems with mbw_wd < 7.
>
> resctrl is introducing resctrl_arch_preconvert_bw() to allow the arch code
> to specify the conversion resctrl does to the user-provided bandwidth
> value. Add the MPAM version of resctrl_arch_preconvert_bw(). This does no
> conversion.
>
> Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> ---
> Changes since v3:
> Parameter order switch (Reinette)
> Add Reinette's R-b
>
> Changes since v4:
> Add missing tearoff divider, ---
> ---
>   drivers/resctrl/mpam_resctrl.c | 5 +++++
>   1 file changed, 5 insertions(+)
Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>