[PATCH v4 13/31] fs/resctrl: Add support for additional monitor event display formats

[Tony Luck <tony.luck@intel.com>]

Resctrl was written with the assumption that all monitor events
can be displayed as unsigned decimal integers.

Some telemetry events provide greater precision where architecture code
uses a fixed point format with 18 binary places.

Add a "display_format" field to struct mon_evt which can specify
that the value for the event be displayed as an integer for legacy
events, or as a floating point value with six decimal places converted
from the fixed point format received from architecture code.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 include/linux/resctrl_types.h |  5 +++++
 fs/resctrl/internal.h         |  2 ++
 fs/resctrl/ctrlmondata.c      | 24 +++++++++++++++++++++++-
 fs/resctrl/monitor.c          | 21 ++++++++++++---------
 4 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/include/linux/resctrl_types.h b/include/linux/resctrl_types.h
index 5ef14a24008c..6245034f6c76 100644
--- a/include/linux/resctrl_types.h
+++ b/include/linux/resctrl_types.h
@@ -50,4 +50,9 @@ enum resctrl_event_id {
 #define QOS_NUM_MBM_EVENTS	(QOS_L3_MBM_LOCAL_EVENT_ID - QOS_L3_MBM_TOTAL_EVENT_ID + 1)
 #define MBM_EVENT_IDX(evt)	((evt) - QOS_L3_MBM_TOTAL_EVENT_ID)
 
+/* Event value display formats */
+enum resctrl_event_fmt {
+	EVT_FORMAT_U64,
+	EVT_FORMAT_U46_18,
+};
 #endif /* __LINUX_RESCTRL_TYPES_H */
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index d8aa69b42c74..aaa74a17257d 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -73,6 +73,7 @@ static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
  * @configurable:	true if the event is configurable
  * @enabled:		true if the event is enabled
  * @any_cpu:		true if the event can be read from any CPU
+ * @display_format:	format to display value to users
  * @list:		entry in &rdt_resource->evt_list
  */
 struct mon_evt {
@@ -82,6 +83,7 @@ struct mon_evt {
 	bool			configurable;
 	bool			enabled;
 	bool			any_cpu;
+	enum resctrl_event_fmt	display_format;
 	struct list_head	list;
 };
 
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 7a2957b9c13e..1544c103446b 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -569,6 +569,28 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 	resctrl_arch_mon_ctx_free(r, evt->evtid, rr->arch_mon_ctx);
 }
 
+#define NUM_FRAC_BITS	18
+#define FRAC_MASK	GENMASK(NUM_FRAC_BITS - 1, 0)
+
+static void print_event_value(struct seq_file *m, enum resctrl_event_fmt type, u64 val)
+{
+	u64 frac;
+
+	switch (type) {
+	case EVT_FORMAT_U64:
+		seq_printf(m, "%llu\n", val);
+		break;
+	case EVT_FORMAT_U46_18:
+		frac = val & FRAC_MASK;
+		frac = frac * 1000000;
+		/* round values up to nearest decimal representation */
+		frac += 1ul << (NUM_FRAC_BITS - 1);
+		frac >>= NUM_FRAC_BITS;
+		seq_printf(m, "%llu.%06llu\n", val >> NUM_FRAC_BITS, frac);
+		break;
+	}
+}
+
 int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 {
 	struct kernfs_open_file *of = m->private;
@@ -637,7 +659,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 	else if (rr.err == -EINVAL)
 		seq_puts(m, "Unavailable\n");
 	else
-		seq_printf(m, "%llu\n", rr.val);
+		print_event_value(m, evt->display_format, rr.val);
 
 out:
 	rdtgroup_kn_unlock(of->kn);
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index e903d3c076ee..be78488a15e5 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -844,19 +844,22 @@ static void dom_data_exit(struct rdt_resource *r)
 
 struct mon_evt mon_event_all[QOS_NUM_EVENTS] = {
 	[QOS_L3_OCCUP_EVENT_ID] = {
-		.name	= "llc_occupancy",
-		.evtid	= QOS_L3_OCCUP_EVENT_ID,
-		.rid	= RDT_RESOURCE_L3,
+		.name		= "llc_occupancy",
+		.evtid		= QOS_L3_OCCUP_EVENT_ID,
+		.rid		= RDT_RESOURCE_L3,
+		.display_format	= EVT_FORMAT_U64,
 	},
 	[QOS_L3_MBM_TOTAL_EVENT_ID] = {
-		.name	= "mbm_total_bytes",
-		.evtid	= QOS_L3_MBM_TOTAL_EVENT_ID,
-		.rid	= RDT_RESOURCE_L3,
+		.name		= "mbm_total_bytes",
+		.evtid		= QOS_L3_MBM_TOTAL_EVENT_ID,
+		.rid		= RDT_RESOURCE_L3,
+		.display_format	= EVT_FORMAT_U64,
 	},
 	[QOS_L3_MBM_LOCAL_EVENT_ID] = {
-		.name	= "mbm_local_bytes",
-		.evtid	= QOS_L3_MBM_LOCAL_EVENT_ID,
-		.rid	= RDT_RESOURCE_L3,
+		.name		= "mbm_local_bytes",
+		.evtid		= QOS_L3_MBM_LOCAL_EVENT_ID,
+		.rid		= RDT_RESOURCE_L3,
+		.display_format	= EVT_FORMAT_U64,
 	},
 };
 
-- 
2.48.1