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 v10 1/5] arm64: arm_pmu: remove unnecessary isb instruction
Date: Mon, 14 Jan 2019 16:11:44 +0000 [thread overview]
Message-ID: <1547482308-29839-2-git-send-email-andrew.murray@arm.com> (raw)
In-Reply-To: <1547482308-29839-1-git-send-email-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 1620a37..1c71796 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)
--
2.7.4
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next prev parent reply other threads:[~2019-01-14 16:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-14 16:11 [PATCH v10 0/5] arm64: Support perf event modifiers :G and :H Andrew Murray
2019-01-14 16:11 ` Andrew Murray [this message]
2019-01-14 16:11 ` [PATCH v10 2/5] arm64: KVM: encapsulate kvm_cpu_context in kvm_host_data Andrew Murray
2019-01-14 16:11 ` [PATCH v10 3/5] arm64: KVM: add accessors to track guest/host only counters Andrew Murray
2019-01-14 16:11 ` [PATCH v10 4/5] arm64: arm_pmu: Add support for exclude_host/exclude_guest attributes Andrew Murray
2019-02-11 11:26 ` Will Deacon
2019-02-18 21:53 ` Christoffer Dall
2019-02-20 16:15 ` Andrew Murray
2019-02-26 12:44 ` Christoffer Dall
2019-03-04 11:14 ` Andrew Murray
2019-03-05 11:45 ` Andrew Murray
2019-03-06 8:42 ` Christoffer Dall
2019-01-14 16:11 ` [PATCH v10 5/5] arm64: KVM: Enable support for :G/:H perf event modifiers Andrew Murray
2019-02-18 22:00 ` Christoffer Dall
2019-03-04 9:40 ` Andrew Murray
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