[PATCH v3 04/13] perf/x86/amd: add branch-brs helper event for Fam19h BRS

Stephane Eranian
2021-12-01T01:02:45Z

This patch adds a pseudo event called branch-brs to help use the FAM Fam19h
Branch Sampling feature (BRS). BRS samples taken branches, so it is best used
when sampling on a retired taken branch event (0xc4) which is what BRS
captures. Instead of trying to remember the event code or actual event name,
users can simply do:

$ perf record -b -e cpu/branch-brs/ -c 1000037 .....

Signed-off-by: Stephane Eranian <eranian@google.com>
---
arch/x86/events/amd/core.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 44d8f618bb3e..597defee1e02 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1105,8 +1105,24 @@ static struct attribute_group group_caps_amd_brs = {
.is_visible = amd_brs_is_visible,
};

+#define AMD_FAM19H_BRS_EVENT 0xc4 /* Fam19h RETIRED_TAKEN_BRANCH_INSTRUCTIONS */
+EVENT_ATTR_STR(branch-brs, amd_branch_brs,
+ "event=" __stringify(AMD_FAM19H_BRS_EVENT)"\n");
+
+static struct attribute *amd_brs_events_attrs[] = {
+ EVENT_PTR(amd_branch_brs),
+ NULL,
+};
+
+static struct attribute_group group_events_amd_brs = {
+ .name = "events",
+ .attrs = amd_brs_events_attrs,
+ .is_visible = amd_brs_is_visible,
+};
+
static const struct attribute_group *amd_attr_update[] = {
&group_caps_amd_brs,
+ &group_events_amd_brs,
NULL,
};

--
2.34.0.rc2.393.gf8c9666880-goog