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

[Babu Moger]

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@xxxxxxx>
> > Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 # [2]
> > ---
>
> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Thanks
Babu