From: Marc Zyngier <maz@kernel.org>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: will@kernel.org, julien.thierry.kdev@gmail.com,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, james.morse@arm.com,
suzuki.poulose@arm.com, mark.rutland@arm.com
Subject: Re: [PATCH kvmtool 9/9] arm64: Add support for KVM_ARM_VCPU_PMU_V3_SET_PMU
Date: Tue, 04 Jan 2022 14:39:59 +0000 [thread overview]
Message-ID: <87h7ajva2o.wl-maz@kernel.org> (raw)
In-Reply-To: <20211115165705.195736-10-alexandru.elisei@arm.com>
On Mon, 15 Nov 2021 16:57:05 +0000,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>
> The KVM_ARM_VCPU_PMU_V3_CTRL(KVM_ARM_VCPU_PMU_V3_SET_PMU) VCPU ioctl is
> used to assign a physical PMU to the events that KVM creates when emulating
> the PMU for that VCPU. This is useful on heterogeneous systems, when there
> is more than one hardware PMU present.
>
> The assumption that is made in the implementation is that the user will
> pin the kvmtool process on a set of CPUs that share the same PMU. This
> allows kvmtool to set the same PMU for all VCPUs from the main thread,
> instead of in the individual VCPU threads.
May I suggest a slightly different use model? Ideally, you'd be able
to run the vcpu threads on the CPUs matching the PMU affinity, and
leave all the other threads to roam on other CPUs.
With your implementation, the whole of kvmtool gets stuck to a given
CPU type, which can be problematic.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2022-01-04 14:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 16:56 [PATCH kvmtool 0/9] arm64: Improve PMU support on heterogeneous systems Alexandru Elisei
2021-11-15 16:56 ` [PATCH kvmtool 1/9] linux/err.h: Add missing stdbool.h include Alexandru Elisei
2021-11-15 16:56 ` [PATCH kvmtool 2/9] arm: Move arch specific VCPU features to the arch specific function Alexandru Elisei
2021-11-15 16:56 ` [PATCH kvmtool 3/9] arm: Get rid of the ARM_VCPU_FEATURE_FLAGS() macro Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 4/9] arm: Make the PMUv3 emulation code arm64 specific Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 5/9] arm64: Rework set_pmu_attr() Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 6/9] util: Add basic cpumask functions Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 7/9] util: Add cpulist_parse() Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 8/9] update_headers.sh: Sync headers with Linux v5.16-rc1 + SET_PMU attribute Alexandru Elisei
2021-11-15 16:57 ` [PATCH kvmtool 9/9] arm64: Add support for KVM_ARM_VCPU_PMU_V3_SET_PMU Alexandru Elisei
2022-01-04 14:39 ` Marc Zyngier [this message]
2022-01-07 12:10 ` Alexandru Elisei
2022-01-08 13:27 ` Marc Zyngier
2022-01-08 16:03 ` Alexandru Elisei
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