Re: [RFC v2] arm,x86,fs/resctrl: Generic schema description Proof of Concept

[Fenghua Yu <fenghuay@nvidia.com>]

Hi, Chen,

On 8/9/26 20:02, Chen, Yu C wrote:
> Hi Fenghua,
> On 8/10/2026 10:55 AM, Fenghua Yu wrote:
> 
> [ ... ]
> 
>> struct resctrl_ctrl {
>> ...
>>          struct list_head        emulated_by;
>> };
>>
>> Does this mean a legacy resctrl control can be emulated by a few 
>> resctrl controls (which is stored in the list)?
>>
>> e.g. legacy MB control can be emulated by a few controls? I thought 
>> "MB:" line is emulated by only one native control. e.g. "MB:" line is 
>> emulated by "MB_NODE:" line.
>>
> 
> If I understand correctly, for region-aware RDT, the legacy MB control may
> be emulated collectively by region0_control, region1_control, ..., 
> regionN_control.
> In the original definition, MB represents the traffic that misses the L3 
> cache and
> is refilled from all sources, which could include DRAM (region0), CXL 
> (region1),
> and others.
I may misunderstand "emulation" concept here.

I was thinking emulation mode is for backward compatibility, i.e. a 
native MB control is emulating "MB:" line: writing and reading both 
lines are same. So legacy user app won't be broken on new control.

For a list of resctrl controls (region0_control, region1_control, etc), 
which one is for legacy "MB:" control so that reading/wring the control 
is same as writing/reading "MB:"line?

Thanks.

-Fenghua