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From:   Peter Newman <peternewman@google.com>
Date:   Tue, 6 Jun 2023 15:36:00 +0200
Message-ID: <CALPaoCgF25n-Rnxxd-Pwo+675LLdSGt-sC2d7C2voS6ueNnL2A@mail.gmail.com>
Subject: Re: [PATCH v1 7/9] x86/resctrl: Assign HW RMIDs to CPUs for soft RMID
To:     Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>
Cc:     Babu Moger <babu.moger@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Stephane Eranian <eranian@google.com>,
        James Morse <james.morse@arm.com>,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
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On Fri, Apr 21, 2023 at 4:18=E2=80=AFPM Peter Newman <peternewman@google.co=
m> wrote:
>  static void clear_closid_rmid(int cpu)
>  {
>         struct resctrl_pqr_state *state =3D this_cpu_ptr(&pqr_state);
> @@ -604,7 +636,12 @@ static void clear_closid_rmid(int cpu)
>         state->default_rmid =3D 0;
>         state->cur_closid =3D 0;
>         state->cur_rmid =3D 0;
> -       wrmsr(MSR_IA32_PQR_ASSOC, 0, 0);
> +       state->hw_rmid =3D 0;
> +
> +       if (static_branch_likely(&rdt_soft_rmid_enable_key))
> +               state->hw_rmid =3D determine_hw_rmid_for_cpu(cpu);

clear_closid_rmid() isn't run at mount time, so hw_rmid will be
uninitialized on any CPUs which were already enabled. The static key
was originally set at boot.

(the consequence was that domain bandwidth was the amount recorded on
the first CPU in the domain multiplied by the number of CPUs in the
domain)