Re: [PATCH v4 2/3] arm_mpam: resctrl: Add pass-through resctrl_arch_preconvert_bw()

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

Hi Ben,

On 7/7/26 1:35 AM, Ben Horgan wrote:
> Hi Reinette,
> 
> On 7/6/26 22:33, Reinette Chatre wrote:
>> Hi Ben,
>>
>> On 7/6/26 9:06 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@arm.com>
>>> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
>>>
>>
>> Unfortunately the "---" separator is missing here.
> 
> Another silly mistake.. sorry about that. I've corrected locally and
> will send a respin in a day or two.
No problem. 

When you respin, could you please add a snippet to the cover about expectations
how this series should be merged? This will be the first piece of work that
touches the x86 and Arm driver as well as resctrl fs code. So far I assumed it
will go in via tip but I think it will help to state this from Arm side.
We still need a plan for if/when the Arm side touches the same code though. Thankfully
this work is small.

Reinette