Date:   Thu, 11 Nov 2021 00:44:06 -0800
In-Reply-To: <20211111084415.663951-1-eranian@google.com>
Message-Id: <20211111084415.663951-5-eranian@google.com>
Mime-Version: 1.0
References: <20211111084415.663951-1-eranian@google.com>
Subject: [PATCH v2 04/13] perf/x86/amd: add branch-brs helper event for Fam19h BRS
From:   Stephane Eranian <eranian@google.com>
To:     linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, kim.phillips@amd.com, acme@redhat.com,
        jolsa@redhat.com, songliubraving@fb.com, mpe@ellerman.id.au,
        maddy@linux.ibm.com
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Precedence: bulk

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 8031b9400aaa..d47cc2c6d85c 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1109,8 +1109,24 @@ 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.rc0.344.g81b53c2807-goog