1 files changed, 92 insertions, 0 deletions
diff --git a/arch/x86/include/asm/intel_rdt_sched.h b/arch/x86/include/asm/intel_rdt_sched.h
new file mode 100644
index 000000000000..b4bbf8b21512
--- /dev/null
+++ b/arch/x86/include/asm/intel_rdt_sched.h
@@ -0,0 +1,92 @@
+#ifndef _ASM_X86_INTEL_RDT_SCHED_H
+#define _ASM_X86_INTEL_RDT_SCHED_H
+
+#ifdef CONFIG_INTEL_RDT
+
+#include <linux/sched.h>
+#include <linux/jump_label.h>
+
+#define IA32_PQR_ASSOC	0x0c8f
+
+/**
+ * struct intel_pqr_state - State cache for the PQR MSR
+ * @cur_rmid:		The cached Resource Monitoring ID
+ * @cur_closid:	The cached Class Of Service ID
+ * @default_rmid:	The user assigned Resource Monitoring ID
+ * @default_closid:	The user assigned cached Class Of Service ID
+ *
+ * The upper 32 bits of IA32_PQR_ASSOC contain closid and the
+ * lower 10 bits rmid. The update to IA32_PQR_ASSOC always
+ * contains both parts, so we need to cache them. This also
+ * stores the user configured per cpu CLOSID and RMID.
+ *
+ * The cache also helps to avoid pointless updates if the value does
+ * not change.
+ */
+struct intel_pqr_state {
+	u32			cur_rmid;
+	u32			cur_closid;
+	u32			default_rmid;
+	u32			default_closid;
+};
+
+DECLARE_PER_CPU(struct intel_pqr_state, pqr_state);
+
+DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
+DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key);
+DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
+
+/*
+ * __intel_rdt_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR
+ *
+ * Following considerations are made so that this has minimal impact
+ * on scheduler hot path:
+ * - This will stay as no-op unless we are running on an Intel SKU
+ *   which supports resource control or monitoring and we enable by
+ *   mounting the resctrl file system.
+ * - Caches the per cpu CLOSid/RMID values and does the MSR write only
+ *   when a task with a different CLOSid/RMID is scheduled in.
+ * - We allocate RMIDs/CLOSids globally in order to keep this as
+ *   simple as possible.
+ * Must be called with preemption disabled.
+ */
+static void __intel_rdt_sched_in(void)
+{
+	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
+	u32 closid = state->default_closid;
+	u32 rmid = state->default_rmid;
+
+	/*
+	 * If this task has a closid/rmid assigned, use it.
+	 * Else use the closid/rmid assigned to this cpu.
+	 */
+	if (static_branch_likely(&rdt_alloc_enable_key)) {
+		if (current->closid)
+			closid = current->closid;
+	}
+
+	if (static_branch_likely(&rdt_mon_enable_key)) {
+		if (current->rmid)
+			rmid = current->rmid;
+	}
+
+	if (closid != state->cur_closid || rmid != state->cur_rmid) {
+		state->cur_closid = closid;
+		state->cur_rmid = rmid;
+		wrmsr(IA32_PQR_ASSOC, rmid, closid);
+	}
+}
+
+static inline void intel_rdt_sched_in(void)
+{
+	if (static_branch_likely(&rdt_enable_key))
+		__intel_rdt_sched_in();
+}
+
+#else
+
+static inline void intel_rdt_sched_in(void) {}
+
+#endif /* CONFIG_INTEL_RDT */
+
+#endif /* _ASM_X86_INTEL_RDT_SCHED_H */