[RFC PATCH 14/23] thermal: intel: hfi: Update the class of the current task

[Ricardo Neri]

Support the interfaces of the scheduler for classes of tasks. If an Intel
processor supports Intel Thread Director, then it supports classes of
tasks.

Use the hardware resources that Intel Thread Director provides to assign
a class to the currently running task.

Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
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-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/topology.h   |  8 +++++++
 drivers/thermal/intel/intel_hfi.c | 35 +++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 458c891a8273..9c6df4fd9414 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -227,4 +227,12 @@ void init_freq_invariance_cppc(void);
 #define arch_init_invariance_cppc init_freq_invariance_cppc
 #endif
 
+#ifdef CONFIG_INTEL_THREAD_DIRECTOR
+int intel_hfi_has_task_classes(void);
+void intel_hfi_update_task_class(struct task_struct *curr, bool smt_siblings_idle);
+
+#define arch_has_task_classes intel_hfi_has_task_classes
+#define arch_update_task_class intel_hfi_update_task_class
+#endif
+
 #endif /* _ASM_X86_TOPOLOGY_H */
diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
index 4bafe6848d5d..f46d9331f912 100644
--- a/drivers/thermal/intel/intel_hfi.c
+++ b/drivers/thermal/intel/intel_hfi.c
@@ -73,6 +73,17 @@ union cpuid6_edx {
 	u32 full;
 };
 
+#ifdef CONFIG_INTEL_THREAD_DIRECTOR
+union hfi_thread_feedback_char_msr {
+	struct {
+		u8	classid;
+		u64	__reserved:55;
+		u8	valid:1;
+	} split;
+	u64 full;
+};
+#endif
+
 /**
  * struct hfi_cpu_data - HFI capabilities per CPU
  * @perf_cap:		Performance capability
@@ -172,6 +183,30 @@ static struct workqueue_struct *hfi_updates_wq;
 #define HFI_UPDATE_INTERVAL		HZ
 #define HFI_MAX_THERM_NOTIFY_COUNT	16
 
+#ifdef CONFIG_INTEL_THREAD_DIRECTOR
+int intel_hfi_has_task_classes(void)
+{
+	return cpu_feature_enabled(X86_FEATURE_ITD);
+}
+
+void intel_hfi_update_task_class(struct task_struct *curr, bool smt_siblings_idle)
+{
+	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;
+
+	curr->class = msr.split.classid;
+}
+#endif /* CONFIG_INTEL_THREAD_DIRECTOR */
+
 static void get_hfi_caps(struct hfi_instance *hfi_instance,
 			 struct thermal_genl_cpu_caps *cpu_caps)
 {
-- 
2.25.1