[PATCH 26/32] perf/x86/intel/cqm: integrate CQM cgroups with scheduler

[David Carrillo-Cisneros <davidcc@google.com>]

Allow monitored cgroups to update the PQR MSR during task switch even
without an associated perf_event.

The package RMID for the current monr associated with a monitored
cgroup is written to hw during task switch (after perf_events is run)
if perf_event did not write a RMID for an event.

perf_event and any other caller of pqr_cache_update_rmid can update the
CPU's RMID using one of two modes:
  - PQR_RMID_MODE_NOEVENT: A RMID that do not correspond to an event.
    e.g. the RMID of the root pmonr when no event is scheduled.
  - PQR_RMID_MODE_EVENT:   A RMID used by an event. Set during pmu::add
unset on pmu::del. This mode prevents from using a non-event
cgroup RMID.

This patch also introduces caching of writes to PQR MSR within the per-pcu
pqr state variable. This interface to update RMIDs and CLOSIDs will be
also utilized in upcoming versions of Intel's MBM and CAT drivers.

Reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 arch/x86/events/intel/cqm.c       | 65 +++++++++++++++++++++++++++++----------
 arch/x86/events/intel/cqm.h       |  2 --
 arch/x86/include/asm/pqr_common.h | 53 +++++++++++++++++++++++++++----
 arch/x86/kernel/cpu/pqr_common.c  | 46 +++++++++++++++++++++++----
 4 files changed, 135 insertions(+), 31 deletions(-)

diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c
index daf9fdf..4ece0a4 100644
--- a/arch/x86/events/intel/cqm.c
+++ b/arch/x86/events/intel/cqm.c
@@ -198,19 +198,6 @@ static inline int cqm_prmid_update(struct prmid *prmid)
 	return __cqm_prmid_update(prmid, __rmid_min_update_time);
 }
 
-/*
- * Updates caller cpu's cache.
- */
-static inline void __update_pqr_prmid(struct prmid *prmid)
-{
-	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-
-	if (state->rmid == prmid->rmid)
-		return;
-	state->rmid = prmid->rmid;
-	wrmsr(MSR_IA32_PQR_ASSOC, prmid->rmid, state->closid);
-}
-
 static inline bool __valid_pkg_id(u16 pkg_id)
 {
 	return pkg_id < PQR_MAX_NR_PKGS;
@@ -2531,12 +2518,11 @@ static inline bool cqm_group_leader(struct perf_event *event)
 static inline void __intel_cqm_event_start(
 	struct perf_event *event, union prmid_summary summary)
 {
-	u16 pkg_id = topology_physical_package_id(smp_processor_id());
 	if (!(event->hw.state & PERF_HES_STOPPED))
 		return;
-
 	event->hw.state &= ~PERF_HES_STOPPED;
-	__update_pqr_prmid(__prmid_from_rmid(pkg_id, summary.sched_rmid));
+
+	pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_EVENT);
 }
 
 static void intel_cqm_event_start(struct perf_event *event, int mode)
@@ -2566,7 +2552,7 @@ static void intel_cqm_event_stop(struct perf_event *event, int mode)
 	/* Occupancy of CQM events is obtained at read. No need to read
 	 * when event is stopped since read on inactive cpus succeed.
 	 */
-	__update_pqr_prmid(__prmid_from_rmid(pkg_id, summary.sched_rmid));
+	pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
 }
 
 static int intel_cqm_event_add(struct perf_event *event, int mode)
@@ -2977,6 +2963,8 @@ static void intel_cqm_cpu_starting(unsigned int cpu)
 
 	state->rmid = 0;
 	state->closid = 0;
+	state->next_rmid = 0;
+	state->next_closid = 0;
 
 	/* XXX: lock */
 	/* XXX: Make sure this case is handled when hotplug happens. */
@@ -3152,6 +3140,12 @@ static int __init intel_cqm_init(void)
 	pr_info("Intel CQM monitoring enabled with at least %u rmids per package.\n",
 		min_max_rmid + 1);
 
+	/* Make sure pqr_common_enable_key is enabled after
+	 * cqm_initialized_key.
+	 */
+	barrier();
+
+	static_branch_enable(&pqr_common_enable_key);
 	return ret;
 
 error_init_mutex:
@@ -3163,4 +3157,41 @@ error:
 	return ret;
 }
 
+/* Schedule task without a CQM perf_event. */
+inline void __intel_cqm_no_event_sched_in(void)
+{
+#ifdef CONFIG_CGROUP_PERF
+	struct monr *monr;
+	struct pmonr *pmonr;
+	union prmid_summary summary;
+	u16 pkg_id = topology_physical_package_id(smp_processor_id());
+	struct pmonr *root_pmonr = monr_hrchy_root->pmonrs[pkg_id];
+
+	/* Assume CQM enabled is likely given that PQR is enabled. */
+	if (!static_branch_likely(&cqm_initialized_key))
+		return;
+
+	/* Safe to call from_task since we are in scheduler lock. */
+	monr = monr_from_perf_cgroup(perf_cgroup_from_task(current, NULL));
+	pmonr = monr->pmonrs[pkg_id];
+
+	/* Utilize most up to date pmonr summary. */
+	monr_hrchy_get_next_prmid_summary(pmonr);
+	summary.value = atomic64_read(&pmonr->prmid_summary_atomic);
+
+	if (!prmid_summary__is_mon_active(summary))
+		goto no_rmid;
+
+	if (WARN_ON_ONCE(!__valid_rmid(pkg_id, summary.sched_rmid)))
+		goto no_rmid;
+
+	pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
+	return;
+
+no_rmid:
+	summary.value = atomic64_read(&root_pmonr->prmid_summary_atomic);
+	pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
+#endif
+}
+
 device_initcall(intel_cqm_init);
diff --git a/arch/x86/events/intel/cqm.h b/arch/x86/events/intel/cqm.h
index 0f3da94..e1f8bd0 100644
--- a/arch/x86/events/intel/cqm.h
+++ b/arch/x86/events/intel/cqm.h
@@ -82,8 +82,6 @@ union prmid_summary {
 	};
 };
 
-# define INVALID_RMID (-1)
-
 /* A pmonr in (U)state has no sched_rmid, read_rmid can be 0 or INVALID_RMID
  * depending on whether monitoring is active or not.
  */
diff --git a/arch/x86/include/asm/pqr_common.h b/arch/x86/include/asm/pqr_common.h
index f770637..abbb235 100644
--- a/arch/x86/include/asm/pqr_common.h
+++ b/arch/x86/include/asm/pqr_common.h
@@ -3,31 +3,72 @@
 
 #if defined(CONFIG_INTEL_RDT)
 
+#include <linux/jump_label.h>
 #include <linux/types.h>
 #include <asm/percpu.h>
+#include <asm/msr.h>
 
 #define MSR_IA32_PQR_ASSOC	0x0c8f
+#define INVALID_RMID		(-1)
+#define INVALID_CLOSID		(-1)
+
+
+extern struct static_key_false pqr_common_enable_key;
+
+enum intel_pqr_rmid_mode {
+	/* RMID has no perf_event associated. */
+	PQR_RMID_MODE_NOEVENT = 0,
+	/* RMID has a perf_event associated. */
+	PQR_RMID_MODE_EVENT
+};
 
 /**
  * struct intel_pqr_state - State cache for the PQR MSR
- * @rmid:		The cached Resource Monitoring ID
- * @closid:		The cached Class Of Service ID
+ * @rmid:		Last rmid written to hw.
+ * @next_rmid:		Next rmid to write to hw.
+ * @next_rmid_mode:	Next rmid's mode.
+ * @closid:		The current Class Of Service ID
+ * @next_closid:	The Class Of Service ID to use.
  *
  * The upper 32 bits of MSR_IA32_PQR_ASSOC contain closid and the
  * lower 10 bits rmid. The update to MSR_IA32_PQR_ASSOC always
  * contains both parts, so we need to cache them.
  *
- * The cache also helps to avoid pointless updates if the value does
- * not change.
+ * The cache also helps to avoid pointless updates if the value does not
+ * change. It also keeps track of the type of RMID set (event vs no event)
+ * used to determine when a cgroup RMID is required.
  */
 struct intel_pqr_state {
-	u32			rmid;
-	u32			closid;
+	u32				rmid;
+	u32				next_rmid;
+	enum intel_pqr_rmid_mode	next_rmid_mode;
+	u32				closid;
+	u32				next_closid;
 };
 
 DECLARE_PER_CPU(struct intel_pqr_state, pqr_state);
 
 #define PQR_MAX_NR_PKGS		8
 
+void __pqr_update(void);
+
+inline void __intel_cqm_no_event_sched_in(void);
+
+inline void pqr_cache_update_rmid(u32 rmid, enum intel_pqr_rmid_mode mode);
+
+inline void pqr_cache_update_closid(u32 closid);
+
+static inline void pqr_update(void)
+{
+	if (static_branch_unlikely(&pqr_common_enable_key))
+		__pqr_update();
+}
+
+#else
+
+static inline void pqr_update(void)
+{
+}
+
 #endif
 #endif
diff --git a/arch/x86/kernel/cpu/pqr_common.c b/arch/x86/kernel/cpu/pqr_common.c
index 9eff5d9..d91c127 100644
--- a/arch/x86/kernel/cpu/pqr_common.c
+++ b/arch/x86/kernel/cpu/pqr_common.c
@@ -1,9 +1,43 @@
 #include <asm/pqr_common.h>
 
-/*
- * The cached intel_pqr_state is strictly per CPU and can never be
- * updated from a remote CPU. Both functions which modify the state
- * (intel_cqm_event_start and intel_cqm_event_stop) are called with
- * interrupts disabled, which is sufficient for the protection.
- */
 DEFINE_PER_CPU(struct intel_pqr_state, pqr_state);
+
+DEFINE_STATIC_KEY_FALSE(pqr_common_enable_key);
+
+inline void pqr_cache_update_rmid(u32 rmid, enum intel_pqr_rmid_mode mode)
+{
+	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
+
+	state->next_rmid_mode = mode;
+	state->next_rmid = rmid;
+}
+
+inline void pqr_cache_update_closid(u32 closid)
+{
+	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
+
+	state->next_closid = closid;
+}
+
+/* Update hw's RMID using cgroup's if perf_event did not.
+ * Sync pqr cache with MSR.
+ */
+inline void __pqr_update(void)
+{
+	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
+
+	/* If perf_event has set a next_rmid that is used, do not try
+	 * to obtain another one from current task.
+	 */
+	if (state->next_rmid_mode == PQR_RMID_MODE_NOEVENT)
+		__intel_cqm_no_event_sched_in();
+
+	/* __intel_cqm_no_event_sched_in might have changed next_rmid. */
+	if (state->rmid == state->next_rmid &&
+	    state->closid == state->next_closid)
+		return;
+
+	state->rmid = state->next_rmid;
+	state->closid = state->next_closid;
+	wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, state->closid);
+}
-- 
2.8.0.rc3.226.g39d4020