From: Marc Zyngier <maz@kernel.org>
To: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: Reiji Watanabe <reijiw@google.com>,
<kvmarm@lists.cs.columbia.edu>, <kvmarm@lists.linux.dev>,
<kvm@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Ricardo\ Koller" <ricarkol@google.com>,
Oliver Upton <oliver.upton@linux.dev>,
"Jing\ Zhang" <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>
Subject: Re: [PATCH 0/7] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU
Date: Tue, 03 Jan 2023 12:47:18 +0000 [thread overview]
Message-ID: <86y1qj7pk9.wl-maz@kernel.org> (raw)
In-Reply-To: <20230103124034.000027aa@Huawei.com>
On Tue, 03 Jan 2023 12:40:34 +0000,
Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:
>
> On Thu, 29 Dec 2022 19:59:21 -0800
> Reiji Watanabe <reijiw@google.com> wrote:
>
> > The goal of this series is to allow userspace to limit the number
> > of PMU event counters on the vCPU.
>
> Hi Rieji,
>
> Why do you want to do this?
>
> I can conjecture a bunch of possible reasons, but they may not
> match up with your use case. It would be useful to have that information
> in the cover letter.
The most obvious use case is to support migration across systems that
implement different numbers of counters. Similar reasoning could also
apply to the debug infrastructure (watchpoints, breakpoints).
In any case, being able to decouple the VM from the underlying HW
within the extent that the architecture permits it seems like a
valuable goal.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2023-01-03 14:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-30 3:59 [PATCH 0/7] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU Reiji Watanabe
2022-12-30 3:59 ` [PATCH 1/7] KVM: arm64: PMU: Have reset_pmu_reg() to clear a register Reiji Watanabe
2023-01-08 19:07 ` Oliver Upton
2023-01-10 5:50 ` Reiji Watanabe
2022-12-30 3:59 ` [PATCH 2/7] KVM: arm64: PMU: Use reset_pmu_reg() for PMUSERENR_EL0 and PMCCFILTR_EL0 Reiji Watanabe
2023-01-08 19:13 ` Oliver Upton
2023-01-10 1:17 ` Reiji Watanabe
2023-01-10 1:46 ` Oliver Upton
2022-12-30 3:59 ` [PATCH 3/7] KVM: arm64: PMU: Preserve vCPU's PMCR_EL0.N value on vCPU reset Reiji Watanabe
2022-12-30 3:59 ` [PATCH 4/7] tools: arm64: Import perf_event.h Reiji Watanabe
2022-12-30 3:59 ` [PATCH 5/7] KVM: selftests: aarch64: Introduce vpmu_counter_access test Reiji Watanabe
2022-12-30 3:59 ` [PATCH 6/7] KVM: selftests: aarch64: vPMU register test for implemented counters Reiji Watanabe
2022-12-30 3:59 ` [PATCH 7/7] KVM: selftests: aarch64: vPMU register test for unimplemented counters Reiji Watanabe
2023-01-03 12:40 ` [PATCH 0/7] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU Jonathan Cameron
2023-01-03 12:47 ` Marc Zyngier [this message]
2023-01-05 2:59 ` Reiji Watanabe
2023-01-10 2:01 ` Oliver Upton
2023-01-11 0:55 ` Reiji Watanabe
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