From: Will Deacon <will.deacon@arm.com>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Marc Zyngier <marc.zyngier@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Julien Thierry <julien.thierry@arm.com>,
Christoffer Dall <christoffer.dall@arm.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v12 8/8] arm64: docs: document perf event attributes
Date: Thu, 4 Apr 2019 17:21:28 +0100 [thread overview]
Message-ID: <20190404162128.GD27577@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <20190328103731.27264-9-andrew.murray@arm.com>
On Thu, Mar 28, 2019 at 10:37:31AM +0000, Andrew Murray wrote:
> The interaction between the exclude_{host,guest} flags,
> exclude_{user,kernel,hv} flags and presence of VHE can result in
> different exception levels being filtered by the ARMv8 PMU. As this
> can be confusing let's document how they work on arm64.
>
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
> Documentation/arm64/perf.txt | 74 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 74 insertions(+)
> create mode 100644 Documentation/arm64/perf.txt
>
> diff --git a/Documentation/arm64/perf.txt b/Documentation/arm64/perf.txt
> new file mode 100644
> index 000000000000..604446c1f720
> --- /dev/null
> +++ b/Documentation/arm64/perf.txt
> @@ -0,0 +1,74 @@
> +Perf Event Attributes
> +=====================
> +
> +Author: Andrew Murray <andrew.murray@arm.com>
> +Date: 2019-03-06
> +
> +exclude_user
> +------------
> +
> +This attribute excludes userspace.
> +
> +Userspace always runs at EL0 and thus this attribute will exclude EL0.
> +
> +
> +exclude_kernel
> +--------------
> +
> +This attribute excludes the kernel.
> +
> +The kernel runs at EL2 with VHE and EL1 without. Guest kernels always run
> +at EL1.
> +
> +This attribute will exclude EL1 and additionally EL2 on a VHE system.
I find this last sentence a bit confusing, because it can be read to imply
that if you don't set exclude_kernel and you're in a guest on a VHE system,
then you can profile EL2.
> +exclude_hv
> +----------
> +
> +This attribute excludes the hypervisor, we ignore this flag on a VHE system
> +as we consider the host kernel to be the hypervisor.
Similar comment as the above: I don't think this makes sense when you look
at things from the guest perspective.
> +On a non-VHE system we consider the hypervisor to be any code that runs at
> +EL2 which is predominantly used for guest/host transitions.
> +
> +This attribute will exclude EL2 on a non-VHE system.
> +
> +
> +exclude_host / exclude_guest
> +----------------------------
> +
> +This attribute excludes the KVM host.
But there are two attributes...
Will
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next prev parent reply other threads:[~2019-04-04 16:22 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 ` [PATCH v12 1/8] arm64: arm_pmu: remove unnecessary isb instruction Andrew Murray
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 [this message]
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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