linux-kernel - [PATCH 02/13] perf/x86/amd/core: Refactor branch attributes

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Date:   Thu, 11 Aug 2022 17:59:50 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <x86@...nel.org>
CC:     <peterz@...radead.org>, <bp@...en8.de>, <acme@...nel.org>,
        <namhyung@...nel.org>, <jolsa@...nel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>,
        <dave.hansen@...ux.intel.com>, <like.xu.linux@...il.com>,
        <eranian@...gle.com>, <ananth.narayan@....com>,
        <ravi.bangoria@....com>, <santosh.shukla@....com>,
        <sandipan.das@....com>
Subject: [PATCH 02/13] perf/x86/amd/core: Refactor branch attributes

AMD processors that are capable of recording branches support either Branch
Sampling (BRS) or Last Branch Record (LBR). In preparation for adding Last
Branch Record Extension Version 2 (LbrExtV2) support, reuse the "branches"
capability to advertise information about both BRS and LBR but make the
"branch-brs" event exclusive to Family 19h processors that support BRS.

Signed-off-by: Sandipan Das <sandipan.das@....com>
---
 arch/x86/events/amd/core.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index e32a27899e11..2f524cf84528 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1247,23 +1247,25 @@ static ssize_t branches_show(struct device *cdev,
 
 static DEVICE_ATTR_RO(branches);
 
-static struct attribute *amd_pmu_brs_attrs[] = {
+static struct attribute *amd_pmu_branches_attrs[] = {
 	&dev_attr_branches.attr,
 	NULL,
 };
 
 static umode_t
-amd_brs_is_visible(struct kobject *kobj, struct attribute *attr, int i)
+amd_branches_is_visible(struct kobject *kobj, struct attribute *attr, int i)
 {
 	return x86_pmu.lbr_nr ? attr->mode : 0;
 }
 
-static struct attribute_group group_caps_amd_brs = {
+static struct attribute_group group_caps_amd_branches = {
 	.name  = "caps",
-	.attrs = amd_pmu_brs_attrs,
-	.is_visible = amd_brs_is_visible,
+	.attrs = amd_pmu_branches_attrs,
+	.is_visible = amd_branches_is_visible,
 };
 
+#ifdef CONFIG_PERF_EVENTS_AMD_BRS
+
 EVENT_ATTR_STR(branch-brs, amd_branch_brs,
 	       "event=" __stringify(AMD_FAM19H_BRS_EVENT)"\n");
 
@@ -1272,15 +1274,26 @@ static struct attribute *amd_brs_events_attrs[] = {
 	NULL,
 };
 
+static umode_t
+amd_brs_is_visible(struct kobject *kobj, struct attribute *attr, int i)
+{
+	return static_cpu_has(X86_FEATURE_BRS) && x86_pmu.lbr_nr ?
+	       attr->mode : 0;
+}
+
 static struct attribute_group group_events_amd_brs = {
 	.name       = "events",
 	.attrs      = amd_brs_events_attrs,
 	.is_visible = amd_brs_is_visible,
 };
 
+#endif	/* CONFIG_PERF_EVENTS_AMD_BRS */
+
 static const struct attribute_group *amd_attr_update[] = {
-	&group_caps_amd_brs,
+	&group_caps_amd_branches,
+#ifdef CONFIG_PERF_EVENTS_AMD_BRS
 	&group_events_amd_brs,
+#endif
 	NULL,
 };
 
-- 
2.34.1