Re: [RESEND PATCH v4 01/15] x86/resctrl: Support Privilege Level Zero Association (PLZA)

[Babu Moger]

Hi Boris,

On 7/7/26 17:01, Borislav Petkov wrote:
> On Tue, Jul 07, 2026 at 04:50:02PM -0500, Babu Moger wrote:
> > Customers have identified an issue while using the QoS resource control
>
> Please drop the "customers" speak from kernel code.

Will change the text to:

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.


> > feature. If 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 association to be changed during the
> > transition from user mode to kernel mode. This allows the kernel to run
> > using a different CLOSID than user space, which can improve system
> > performance in certain scenarios.
> >
> > 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
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 # [2]
> > Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> > ---
> > v4: Split the patch into 2. This patch only handles x86 changes.
> >      Re-wrote the changelog along the ABMC changes.
> >
> > v3: Code did not change. Patch order changed.
> >      Added documentation link.
> >
> > v2: Rebased on top of the latest tip.
> > ---
> >   arch/x86/include/asm/cpufeatures.h | 1 +
> >   arch/x86/kernel/cpu/scattered.c    | 1 +
> >   2 files changed, 2 insertions(+)
>
> With that addressed:
>
> Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>

Thanks
Babu