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From:   Valentin Schneider <vschneid@redhat.com>
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Subject: [RFC PATCH 03/14] tracing/filters: Enable filtering a scalar field by a cpumask
Date:   Wed,  5 Jul 2023 19:12:45 +0100
Message-Id: <20230705181256.3539027-4-vschneid@redhat.com>
In-Reply-To: <20230705181256.3539027-1-vschneid@redhat.com>
References: <20230705181256.3539027-1-vschneid@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Several events use a scalar field to denote a CPU:
o sched_wakeup.target_cpu
o sched_migrate_task.orig_cpu,dest_cpu
o sched_move_numa.src_cpu,dst_cpu
o ipi_send_cpu.cpu
o ...

Filtering these currently requires using arithmetic comparison functions,
which can be tedious when dealing with interleaved SMT or NUMA CPU ids.

Allow these to be filtered by a user-provided cpumask, which enables e.g.:

$ trace-cmd record -e 'sched_wakeup' -f 'target_cpu & MASK{2,4,6,8-32}'

Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
NOTE: I went with an implicit cpumask conversion of the event field, as
AFAICT predicate_parse() does not support parsing the application of a
function to a field (e.g. 'MASK(target_cpu) & MASK{2,4,6,8-32}')
---
 kernel/trace/trace_events_filter.c | 92 ++++++++++++++++++++++++++----
 1 file changed, 80 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8af00caa363f7..99e111c237a93 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -46,15 +46,19 @@ static const char * ops[] = { OPS };
 enum filter_pred_fn {
 	FILTER_PRED_FN_NOP,
 	FILTER_PRED_FN_64,
+	FILTER_PRED_FN_64_CPUMASK,
 	FILTER_PRED_FN_S64,
 	FILTER_PRED_FN_U64,
 	FILTER_PRED_FN_32,
+	FILTER_PRED_FN_32_CPUMASK,
 	FILTER_PRED_FN_S32,
 	FILTER_PRED_FN_U32,
 	FILTER_PRED_FN_16,
+	FILTER_PRED_FN_16_CPUMASK,
 	FILTER_PRED_FN_S16,
 	FILTER_PRED_FN_U16,
 	FILTER_PRED_FN_8,
+	FILTER_PRED_FN_8_CPUMASK,
 	FILTER_PRED_FN_S8,
 	FILTER_PRED_FN_U8,
 	FILTER_PRED_FN_COMM,
@@ -641,6 +645,37 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
 	return ERR_PTR(ret);
 }
 
+static inline int
+do_filter_cpumask(int op, const struct cpumask *mask, const struct cpumask *cmp)
+{
+	switch (op) {
+	case OP_EQ:
+		return cpumask_equal(mask, cmp);
+	case OP_NE:
+		return !cpumask_equal(mask, cmp);
+	case OP_BAND:
+		return cpumask_intersects(mask, cmp);
+	default:
+		return 0;
+	}
+}
+
+/* Optimisation of do_filter_cpumask() for scalar values */
+static inline int
+do_filter_cpumask_scalar(int op, unsigned int cpu, const struct cpumask *mask)
+{
+	switch (op) {
+	case OP_EQ:
+		return cpumask_equal(mask, cpumask_of(cpu));
+	case OP_NE:
+		return !cpumask_equal(mask, cpumask_of(cpu));
+	case OP_BAND:
+		return cpumask_test_cpu(cpu, mask);
+	default:
+		return 0;
+	}
+}
+
 enum pred_cmp_types {
 	PRED_CMP_TYPE_NOP,
 	PRED_CMP_TYPE_LT,
@@ -684,6 +719,18 @@ static int filter_pred_##type(struct filter_pred *pred, void *event)	\
 	}								\
 }
 
+#define DEFINE_CPUMASK_COMPARISON_PRED(size)					\
+static int filter_pred_##size##_cpumask(struct filter_pred *pred, void *event)	\
+{										\
+	u##size *addr = (u##size *)(event + pred->offset);			\
+	unsigned int cpu = *addr;						\
+										\
+	if (cpu >= nr_cpu_ids)							\
+		return 0;							\
+										\
+	return do_filter_cpumask_scalar(pred->op, cpu, pred->mask);		\
+}
+
 #define DEFINE_EQUALITY_PRED(size)					\
 static int filter_pred_##size(struct filter_pred *pred, void *event)	\
 {									\
@@ -705,6 +752,11 @@ DEFINE_COMPARISON_PRED(u16);
 DEFINE_COMPARISON_PRED(s8);
 DEFINE_COMPARISON_PRED(u8);
 
+DEFINE_CPUMASK_COMPARISON_PRED(64);
+DEFINE_CPUMASK_COMPARISON_PRED(32);
+DEFINE_CPUMASK_COMPARISON_PRED(16);
+DEFINE_CPUMASK_COMPARISON_PRED(8);
+
 DEFINE_EQUALITY_PRED(64);
 DEFINE_EQUALITY_PRED(32);
 DEFINE_EQUALITY_PRED(16);
@@ -889,16 +941,7 @@ static int filter_pred_cpumask(struct filter_pred *pred, void *event)
 	const struct cpumask *mask = (event + loc);
 	const struct cpumask *cmp = pred->mask;
 
-	switch (pred->op) {
-	case OP_EQ:
-		return cpumask_equal(mask, cmp);
-	case OP_NE:
-		return !cpumask_equal(mask, cmp);
-	case OP_BAND:
-		return cpumask_intersects(mask, cmp);
-	default:
-		return 0;
-	}
+	return do_filter_cpumask(pred->op, mask, cmp);
 }
 
 /* Filter predicate for COMM. */
@@ -1349,24 +1392,32 @@ static int filter_pred_fn_call(struct filter_pred *pred, void *event)
 	switch (pred->fn_num) {
 	case FILTER_PRED_FN_64:
 		return filter_pred_64(pred, event);
+	case FILTER_PRED_FN_64_CPUMASK:
+		return filter_pred_64_cpumask(pred, event);
 	case FILTER_PRED_FN_S64:
 		return filter_pred_s64(pred, event);
 	case FILTER_PRED_FN_U64:
 		return filter_pred_u64(pred, event);
 	case FILTER_PRED_FN_32:
 		return filter_pred_32(pred, event);
+	case FILTER_PRED_FN_32_CPUMASK:
+		return filter_pred_32_cpumask(pred, event);
 	case FILTER_PRED_FN_S32:
 		return filter_pred_s32(pred, event);
 	case FILTER_PRED_FN_U32:
 		return filter_pred_u32(pred, event);
 	case FILTER_PRED_FN_16:
 		return filter_pred_16(pred, event);
+	case FILTER_PRED_FN_16_CPUMASK:
+		return filter_pred_16_cpumask(pred, event);
 	case FILTER_PRED_FN_S16:
 		return filter_pred_s16(pred, event);
 	case FILTER_PRED_FN_U16:
 		return filter_pred_u16(pred, event);
 	case FILTER_PRED_FN_8:
 		return filter_pred_8(pred, event);
+	case FILTER_PRED_FN_8_CPUMASK:
+		return filter_pred_8_cpumask(pred, event);
 	case FILTER_PRED_FN_S8:
 		return filter_pred_s8(pred, event);
 	case FILTER_PRED_FN_U8:
@@ -1602,7 +1653,8 @@ static int parse_pred(const char *str, void *data,
 		unsigned int maskstart;
 		char *tmp;
 
-		if (field->filter_type != FILTER_CPUMASK) {
+		if (field->filter_type != FILTER_CPUMASK &&
+		    field->filter_type != FILTER_OTHER) {
 			parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
 			goto err_free;
 		}
@@ -1644,8 +1696,24 @@ static int parse_pred(const char *str, void *data,
 
 		/* Move along */
 		i++;
-		if (field->filter_type == FILTER_CPUMASK)
+		if (field->filter_type == FILTER_CPUMASK) {
 			pred->fn_num = FILTER_PRED_FN_CPUMASK;
+		} else {
+			switch (field->size) {
+			case 8:
+				pred->fn_num = FILTER_PRED_FN_64_CPUMASK;
+				break;
+			case 4:
+				pred->fn_num = FILTER_PRED_FN_32_CPUMASK;
+				break;
+			case 2:
+				pred->fn_num = FILTER_PRED_FN_16_CPUMASK;
+				break;
+			case 1:
+				pred->fn_num = FILTER_PRED_FN_8_CPUMASK;
+				break;
+			}
+		}
 
 	/* This is either a string, or an integer */
 	} else if (str[i] == '\'' || str[i] == '"') {
-- 
2.31.1