[PATCH v3 14/24] thermal: intel: hfi: Update the IPC class of the current task

[Ricardo Neri]

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@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ionela Voinescu <ionela.voinescu@xxxxxxx>
Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Lukasz Luba <lukasz.luba@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tim C. Chen <tim.c.chen@xxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
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;
+}
+
 static int alloc_hfi_ipcc_scores(void)
 {
 	if (!cpu_feature_enabled(X86_FEATURE_ITD))
-- 
2.25.1