Re: [RESEND PATCH v4 03/15] x86/resctrl: Add data structures and definitions for PLZA configuration

[Reinette Chatre]

Hi Babu,

On 8/11/26 2:10 PM, Babu Moger wrote:
> On 8/10/26 21:58, Reinette Chatre wrote:
>> On 7/7/26 2:50 PM, Babu Moger wrote:
>>> Privilege Level Zero Association (PLZA) allows the kernel to use a
>>> different CLOSID (and optionally RMID) than user mode on entry to kernel
>>> mode. The CLOSID/RMID association is programmed per CPU via
>>
>> CLOSID is also optional, no? I am not able to recall now why this is not made
>> optional in this implementation though. Could you please remind me and add
>> it to the changelog for next time?
> 
> 
> Yes, CLOSID is optional as well. Since PLZA was primarily focused on
> allocation, I hadn't considered that use case initially. However,
> there may be scenarios where a user wants to monitor kernel activity
> without affecting or changing the existing allocation configuration.
> That would introduce an additional operating mode(See below).

ok.

I think doing so will simplify supporting the different modes across systems
that may not support allocation or monitoring. 
> INHERIT_CTRL_AND_MON:
> Kernel work inherits the allocation and monitoring from the user space
> task. On x86 this means that kernel work shares the same CLOSID and
> RMID as the user space task. This matches today's resctrl behavior.
> 
> GLOBAL_ASSIGN_CTRL_INHERIT_MON_PER_CPU:
> Kernel work uses a globally assigned allocation while monitoring is
> inherited from the user space task. On x86 this means a CLOSID is
> assigned for kernel work and the RMID is inherited from the user space
> task. Default scope is all online CPUs; a subset may be selected via
> the resctrl group interface. A CTRL_MON group is bound to this mode.
> 
> GLOBAL_ASSIGN_CTRL_ASSIGN_MON_PER_CPU:
> Kernel work uses globally assigned allocation and monitoring. On x86
> this means both CLOSID and RMID are assigned for kernel work. Default
> scope is all online CPUs; a subset may be selected via the resctrl
> group interface. A CTRL_MON or MON group is bound to this mode.
> 
> GLOBAL_INHERIT_CTRL_ASSIGN_MON_PER_CPU:   <--- New mode
> Kernel work inherits the allocation from user task and monitoring is
> globally assigned for kernel work. On x86 this means that kernel
> work shares the same CLOSID as user task and kernel work user
> globally assigned RMID. A MON group is bound to this mode.

I provided comments about this text in following patch. Apart from that,
I think a CTRL_MON or MON group could be assigned to this mode? 

Thank you.

Reinette