linux-kernel - Re: [PATCH v8 00/13] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU

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Date:   Wed, 25 Oct 2023 00:01:12 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Marc Zyngier <maz@...nel.org>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Jing Zhang <jingzhangos@...gle.com>, kvm@...r.kernel.org,
        Reiji Watanabe <reijiw@...gle.com>,
        Shaoqin Huang <shahuang@...hat.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kvmarm@...ts.linux.dev, James Morse <james.morse@....com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Alexandru Elisei <alexandru.elisei@....com>
Subject: Re: [PATCH v8 00/13] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU

On Fri, 20 Oct 2023 21:40:40 +0000, Raghavendra Rao Ananta wrote:
> The goal of this series is to allow userspace to limit the number
> of PMU event counters on the vCPU.  We need this to support migration
> across systems that implement different numbers of counters.
> 
> The number of PMU event counters is indicated in PMCR_EL0.N.
> For a vCPU with PMUv3 configured, its value will be the same as
> the current PE by default.  Userspace can set PMCR_EL0.N for the
> vCPU to any value even with the current KVM using KVM_SET_ONE_REG.
> However, it is practically unsupported, as KVM resets PMCR_EL0.N
> to the host value on vCPU reset and some KVM code uses the host
> value to identify (un)implemented event counters on the vCPU.
> 
> [...]

I've applied this with Marc + I's fixes. I'm happy to toss any fixes
on top of this series if folks spot issues.

[01/13] KVM: arm64: PMU: Introduce helpers to set the guest's PMU
        https://git.kernel.org/kvmarm/kvmarm/c/1616ca6f3c10
[02/13] KVM: arm64: PMU: Set the default PMU for the guest before vCPU reset
        https://git.kernel.org/kvmarm/kvmarm/c/427733579744
[03/13] KVM: arm64: PMU: Add a helper to read a vCPU's PMCR_EL0
        https://git.kernel.org/kvmarm/kvmarm/c/57fc267f1b5c
[04/13] KVM: arm64: PMU: Set PMCR_EL0.N for vCPU based on the associated PMU
        https://git.kernel.org/kvmarm/kvmarm/c/4d20debf9ca1
[05/13] KVM: arm64: Add {get,set}_user for PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR}
        https://git.kernel.org/kvmarm/kvmarm/c/a45f41d754e0
[06/13] KVM: arm64: Sanitize PM{C,I}NTEN{SET,CLR}, PMOVS{SET,CLR} before first run
        https://git.kernel.org/kvmarm/kvmarm/c/27131b199f9f
[07/13] KVM: arm64: PMU: Allow userspace to limit PMCR_EL0.N for the guest
        https://git.kernel.org/kvmarm/kvmarm/c/ea9ca904d24f
[08/13] tools: Import arm_pmuv3.h
        https://git.kernel.org/kvmarm/kvmarm/c/9f4b3273dfbe
[09/13] KVM: selftests: aarch64: Introduce vpmu_counter_access test
        https://git.kernel.org/kvmarm/kvmarm/c/8d0aebe1ca2b
[10/13] KVM: selftests: aarch64: vPMU register test for implemented counters
        https://git.kernel.org/kvmarm/kvmarm/c/ada1ae68262d
[11/13] KVM: selftests: aarch64: vPMU register test for unimplemented counters
        https://git.kernel.org/kvmarm/kvmarm/c/e1cc87206348
[12/13] KVM: selftests: aarch64: vPMU test for validating user accesses
        https://git.kernel.org/kvmarm/kvmarm/c/62708be351fe

--
Best,
Oliver