linux-kernel - [PATCH v1 04/13] perf/x86/amd: add branch-brs helper event for Fam19h BRS

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Date:   Thu,  9 Sep 2021 00:56:51 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, acme@...hat.com, jolsa@...hat.com,
        kim.phillips@....com, namhyung@...nel.org, irogers@...gle.com
Subject: [PATCH v1 04/13] perf/x86/amd: add branch-brs helper event for Fam19h BRS

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@...gle.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 86adb0e879c6..d6d5119260a9 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1106,8 +1106,24 @@ 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,
 };
 
-- 
2.33.0.153.gba50c8fa24-goog