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From: Andrew Murray <andrew.murray@arm.com>
To: Christoffer Dall <christoffer.dall@arm.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>
Cc: Julien Thierry <julien.thierry@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: [PATCH v12 1/8] arm64: arm_pmu: remove unnecessary isb instruction
Date: Thu, 28 Mar 2019 10:37:24 +0000	[thread overview]
Message-ID: <20190328103731.27264-2-andrew.murray@arm.com> (raw)
In-Reply-To: <20190328103731.27264-1-andrew.murray@arm.com>

The armv8pmu_enable_event_counter function issues an isb instruction
after enabling a pair of counters - this doesn't provide any value
and is inconsistent with the armv8pmu_disable_event_counter.

In any case armv8pmu_enable_event_counter is always called with the
PMU stopped. Starting the PMU with armv8pmu_start results in an isb
instruction being issued prior to writing to PMCR_EL0.

Let's remove the unnecessary isb instruction.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
---
 arch/arm64/kernel/perf_event.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 4addb38bc250..cccf4fc86d67 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -533,7 +533,6 @@ static inline void armv8pmu_enable_event_counter(struct perf_event *event)
 	armv8pmu_enable_counter(idx);
 	if (armv8pmu_event_is_chained(event))
 		armv8pmu_enable_counter(idx - 1);
-	isb();
 }
 
 static inline int armv8pmu_disable_counter(int idx)
-- 
2.21.0


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  reply	other threads:[~2019-03-28 10:38 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-28 10:37 [PATCH v12 0/8] arm64: Support perf event modifiers :G and :H Andrew Murray
2019-03-28 10:37 ` Andrew Murray [this message]
2019-03-28 10:37 ` [PATCH v12 2/8] arm64: KVM: encapsulate kvm_cpu_context in kvm_host_data Andrew Murray
2019-03-28 15:28   ` Suzuki K Poulose
2019-04-09 10:52     ` Andrew Murray
2019-04-04 16:09   ` Will Deacon
2019-04-04 16:14     ` Will Deacon
2019-04-04 19:34       ` Andrew Murray
2019-03-28 10:37 ` [PATCH v12 3/8] arm64: KVM: add accessors to track guest/host only counters Andrew Murray
2019-03-28 10:37 ` [PATCH v12 4/8] arm64: arm_pmu: Add !VHE support for exclude_host/exclude_guest attributes Andrew Murray
2019-04-04 16:34   ` Will Deacon
2019-04-04 19:48     ` Andrew Murray
2019-03-28 10:37 ` [PATCH v12 5/8] arm64: KVM: Enable !VHE support for :G/:H perf event modifiers Andrew Murray
2019-03-28 10:37 ` [PATCH v12 6/8] arm64: KVM: Enable VHE " Andrew Murray
2019-04-09 17:52   ` Will Deacon
2019-04-09 19:13     ` Andrew Murray
2019-03-28 10:37 ` [PATCH v12 7/8] arm64: KVM: avoid isb's by using direct pmxevtyper sysreg Andrew Murray
2019-03-28 10:37 ` [PATCH v12 8/8] arm64: docs: document perf event attributes Andrew Murray
2019-04-04 16:21   ` Will Deacon
2019-04-04 19:33     ` Andrew Murray
2019-04-05 12:43       ` Will Deacon
2019-04-09 11:00         ` Andrew Murray

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