[PATCH 24/28] x86/intel_rdt/cqm: Add sched_in support

[Vikas Shivappa]

OS associates an RMID/CLOSid to a task by writing the per CPU
IA32_PQR_ASSOC MSR when a task is scheduled in.

The sched_in code will stay as no-op unless we are running on Intel SKU
which supports either resource control or monitoring and we also enable
them by mounting the resctrl fs.  The per cpu CLOSid/RMID values are
cached and the write is performed only when a task with a different
CLOSid/RMID is scheduled in.

Signed-off-by: Vikas Shivappa <vikas.shivappa@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/intel_rdt_sched.h | 50 ++++++++++++++++++++--------------
 arch/x86/kernel/cpu/intel_rdt.h        |  4 ---
 2 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/intel_rdt_sched.h b/arch/x86/include/asm/intel_rdt_sched.h
index 8c5be01..3badc0a 100644
--- a/arch/x86/include/asm/intel_rdt_sched.h
+++ b/arch/x86/include/asm/intel_rdt_sched.h
@@ -15,7 +15,8 @@
  *
  * 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.
+ * 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.
@@ -30,38 +31,45 @@ struct intel_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 to IA32_PQR_MSR
+ * __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 and we enable by mounting the
- *   resctrl file system.
- * - Caches the per cpu CLOSid values and does the MSR write only
- *   when a task with a different CLOSid is scheduled in.
- *
+ *   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 inline void __intel_rdt_sched_in(void)
+static void __intel_rdt_sched_in(void)
 {
+	struct intel_pqr_state newstate = this_cpu_read(rdt_cpu_default);
+	struct intel_pqr_state *curstate = this_cpu_ptr(&pqr_state);
+
+	/*
+	 * 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)) {
-		struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-		u32 closid;
+		if (current->closid)
+			newstate.closid = current->closid;
+	}
 
-		/*
-		 * If this task has a closid assigned, use it.
-		 * Else use the closid assigned to this cpu.
-		 */
-		closid = current->closid;
-		if (closid == 0)
-			closid = this_cpu_read(rdt_cpu_default.closid);
+	if (static_branch_likely(&rdt_mon_enable_key)) {
+		if (current->rmid)
+			newstate.rmid = current->rmid;
+	}
 
-		if (closid != state->closid) {
-			state->closid = closid;
-			wrmsr(IA32_PQR_ASSOC, state->rmid, closid);
-		}
+	if (newstate.closid != curstate->closid ||
+	    newstate.rmid != curstate->rmid) {
+		*curstate = newstate;
+		wrmsr(IA32_PQR_ASSOC, newstate.rmid, newstate.closid);
 	}
 }
 
diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
index 92a5d30..7fcaa5f 100644
--- a/arch/x86/kernel/cpu/intel_rdt.h
+++ b/arch/x86/kernel/cpu/intel_rdt.h
@@ -22,8 +22,6 @@
 #define RMID_VAL_ERROR			BIT_ULL(63)
 #define RMID_VAL_UNAVAIL		BIT_ULL(62)
 
-DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
-
 /**
  * struct mon_evt - Entry in the event list of a resource
  * @evtid:		event id
@@ -61,8 +59,6 @@ struct rmid_read {
 extern bool rdt_mon_capable;
 extern unsigned int rdt_mon_features;
 
-DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
-
 enum rdt_group_type {
 	RDTCTRL_GROUP = 0,
 	RDTMON_GROUP,
-- 
1.9.1