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    SubjectRe: [PATCH v3 14/24] thermal: intel: hfi: Update the IPC class of the current task
    On Mon, Mar 27, 2023 at 06:42:28PM +0200, Rafael J. Wysocki wrote:
    > On Tue, Feb 7, 2023 at 6:02 AM Ricardo Neri
    > <ricardo.neri-calderon@linux.intel.com> wrote:
    > >
    > > Use Intel Thread Director classification to update the IPC class of a
    > > task. Implement the arch_update_ipcc() interface of the scheduler.
    > >
    > > Cc: Ben Segall <bsegall@google.com>
    > > Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
    > > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
    > > Cc: Ionela Voinescu <ionela.voinescu@arm.com>
    > > Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
    > > Cc: Len Brown <len.brown@intel.com>
    > > Cc: Lukasz Luba <lukasz.luba@arm.com>
    > > Cc: Mel Gorman <mgorman@suse.de>
    > > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    > > Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
    > > Cc: Steven Rostedt <rostedt@goodmis.org>
    > > Cc: Tim C. Chen <tim.c.chen@intel.com>
    > > Cc: Valentin Schneider <vschneid@redhat.com>
    > > Cc: x86@kernel.org
    > > Cc: linux-pm@vger.kernel.org
    > > Cc: linux-kernel@vger.kernel.org
    > > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
    > > ---
    > > Changes since v2:
    > > * Removed the implementation of arch_has_ipc_classes().
    > >
    > > Changes since v1:
    > > * Adjusted the result the classification of Intel Thread Director to start
    > > at class 1. Class 0 for the scheduler means that the task is
    > > unclassified.
    > > * Redefined union hfi_thread_feedback_char_msr to ensure all
    > > bit-fields are packed. (PeterZ)
    > > * Removed CONFIG_INTEL_THREAD_DIRECTOR. (PeterZ)
    > > * Shortened the names of the functions that implement IPC classes.
    > > * Removed argument smt_siblings_idle from intel_hfi_update_ipcc().
    > > (PeterZ)
    > > ---
    > > arch/x86/include/asm/topology.h | 6 ++++++
    > > drivers/thermal/intel/intel_hfi.c | 32 +++++++++++++++++++++++++++++++
    > > 2 files changed, 38 insertions(+)
    > >
    > > diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
    > > index 458c891a8273..ffcdac3f398f 100644
    > > --- a/arch/x86/include/asm/topology.h
    > > +++ b/arch/x86/include/asm/topology.h
    > > @@ -227,4 +227,10 @@ void init_freq_invariance_cppc(void);
    > > #define arch_init_invariance_cppc init_freq_invariance_cppc
    > > #endif
    > >
    > > +#if defined(CONFIG_IPC_CLASSES) && defined(CONFIG_INTEL_HFI_THERMAL)
    > > +void intel_hfi_update_ipcc(struct task_struct *curr);
    > > +
    > > +#define arch_update_ipcc intel_hfi_update_ipcc
    > > +#endif /* defined(CONFIG_IPC_CLASSES) && defined(CONFIG_INTEL_HFI_THERMAL) */
    > > +
    > > #endif /* _ASM_X86_TOPOLOGY_H */
    > > diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
    > > index b06021828892..530dcf57e06e 100644
    > > --- a/drivers/thermal/intel/intel_hfi.c
    > > +++ b/drivers/thermal/intel/intel_hfi.c
    > > @@ -72,6 +72,17 @@ union cpuid6_edx {
    > > u32 full;
    > > };
    > >
    > > +#ifdef CONFIG_IPC_CLASSES
    > > +union hfi_thread_feedback_char_msr {
    > > + struct {
    > > + u64 classid : 8;
    > > + u64 __reserved : 55;
    > > + u64 valid : 1;
    > > + } split;
    > > + u64 full;
    > > +};
    > > +#endif
    > > +
    > > /**
    > > * struct hfi_cpu_data - HFI capabilities per CPU
    > > * @perf_cap: Performance capability
    > > @@ -174,6 +185,27 @@ static struct workqueue_struct *hfi_updates_wq;
    > > #ifdef CONFIG_IPC_CLASSES
    > > static int __percpu *hfi_ipcc_scores;
    > >
    > > +void intel_hfi_update_ipcc(struct task_struct *curr)
    > > +{
    > > + union hfi_thread_feedback_char_msr msr;
    > > +
    > > + /* We should not be here if ITD is not supported. */
    > > + if (!cpu_feature_enabled(X86_FEATURE_ITD)) {
    > > + pr_warn_once("task classification requested but not supported!");
    > > + return;
    > > + }
    > > +
    > > + rdmsrl(MSR_IA32_HW_FEEDBACK_CHAR, msr.full);
    > > + if (!msr.split.valid)
    > > + return;
    > > +
    > > + /*
    > > + * 0 is a valid classification for Intel Thread Director. A scheduler
    > > + * IPCC class of 0 means that the task is unclassified. Adjust.
    > > + */
    > > + curr->ipcc = msr.split.classid + 1;
    > > +}
    >
    > Wouldn't it be better to return the adjusted value from this function
    > and let the caller store it where appropriate?
    >
    > It doesn't look like it is necessary to pass the task_struct pointer to it.

    Judging from this patch alone, yes, it does not make much sense to pass a
    task_struct as argument. In patch 21, however, this function uses various
    members of task_struct and makes it more convenient to have it as argument,
    no?

    >
    > > +
    > > static int alloc_hfi_ipcc_scores(void)
    > > {
    > > if (!cpu_feature_enabled(X86_FEATURE_ITD))
    > > --

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