linux-kernel - [PATCH 1/5] KVM: arm64: Divorce the perf code from oprofile helpers

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Message-Id: <20210414134409.1266357-2-maz@kernel.org>
Date:   Wed, 14 Apr 2021 14:44:05 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org
Cc:     Mark Rutland <mark.rutland@....com>, Will Deacon <will@...nel.org>,
        Rich Felker <dalias@...c.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, nathan@...nel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH 1/5] KVM: arm64: Divorce the perf code from oprofile helpers

KVM/arm64 is the sole user of perf_num_counters(), and really
could do without it. Stop using the obsolete API by relying on
the existing probing code.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kvm/perf.c     | 7 +------
 arch/arm64/kvm/pmu-emul.c | 2 +-
 include/kvm/arm_pmu.h     | 4 ++++
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c
index 739164324afe..b8b398670ef2 100644
--- a/arch/arm64/kvm/perf.c
+++ b/arch/arm64/kvm/perf.c
@@ -50,12 +50,7 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = {
 
 int kvm_perf_init(void)
 {
-	/*
-	 * Check if HW_PERF_EVENTS are supported by checking the number of
-	 * hardware performance counters. This could ensure the presence of
-	 * a physical PMU and CONFIG_PERF_EVENT is selected.
-	 */
-	if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0)
+	if (kvm_pmu_probe_pmuver() != 0xf)
 		static_branch_enable(&kvm_arm_pmu_available);
 
 	return perf_register_guest_info_callbacks(&kvm_guest_cbs);
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index e32c6e139a09..fd167d4f4215 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -739,7 +739,7 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
 	kvm_pmu_create_perf_event(vcpu, select_idx);
 }
 
-static int kvm_pmu_probe_pmuver(void)
+int kvm_pmu_probe_pmuver(void)
 {
 	struct perf_event_attr attr = { };
 	struct perf_event *event;
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 6fd3cda608e4..864b9997efb2 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -61,6 +61,7 @@ int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu,
 int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu,
 			    struct kvm_device_attr *attr);
 int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu);
+int kvm_pmu_probe_pmuver(void);
 #else
 struct kvm_pmu {
 };
@@ -116,6 +117,9 @@ static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
 {
 	return 0;
 }
+
+static inline int kvm_pmu_probe_pmuver(void) { return 0xf; }
+
 #endif
 
 #endif
-- 
2.29.2