Re: [PATCH v6 01/18] x86/cpufeatures: Support Privilege Level Zero Association (PLZA)

[Babu Moger <babu.moger@amd.com>]

Hi Reinette,

Thanks for the review and quick turn-around.

On 10/15/26 09:16, Reinette Chatre wrote:
> Hi Babu,
> 
> On 10/1/26 8:10 AM, Babu Moger wrote:
>> When memory bandwidth associated with a CLOSID is aggressively throttled,
>> and a task with that CLOSID moves into kernel mode, the kernel operations
>> are also aggressively throttled. This can stall forward progress and
>> eventually degrade overall system performance.
>>
>> AMD hardware supports a feature Privilege Level Zero Association (PLZA),
>> which allows the CPU's CLOSID and/or RMID association to be changed during
>> the transition from user mode to kernel mode. This allows the kernel to run
>> using a different CLOSID and/or RMID than user space, which can improve
>> system performance and/or allow kernel work to be monitored separately.
>>
>> Note that PLZA feature associates CLOSID and/or RMID to kernel work, and
>> therefore influences resource allocation and/or monitoring for all
>> resources, not only memory bandwidth.
>>
>> The feature is detected via CPUID_Fn80000020_EBX_x00 [Bit 9]: Privilege
>> Level Zero Association (PLZA).
>>
>> The PLZA feature details are documented in [1] available from [2].
>>
>> [1] AMD64 Zen6 Platform Quality of Service (PQOS) Extensions:
>>      Publication # 69193 Revision: 1.00, Issue Date: March 2026
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 # [2]
>> ---
> 
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> 
Thanks
Babu