From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.linux.dev, Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Mingwei Zhang <mizhang@google.com>,
Colton Lewis <coltonlewis@google.com>,
Raghavendra Rao Ananta <rananta@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 05/14] KVM: arm64: Always allow fixed cycle counter
Date: Tue, 3 Dec 2024 14:32:38 -0800 [thread overview]
Message-ID: <Z0-HBsBgf6WB7x4R@linux.dev> (raw)
In-Reply-To: <87ldwwsbad.wl-maz@kernel.org>
On Tue, Dec 03, 2024 at 09:32:10PM +0000, Marc Zyngier wrote:
> On Tue, 03 Dec 2024 19:32:11 +0000,
> Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > The fixed CPU cycle counter is mandatory for PMUv3, so it doesn't make a
> > lot of sense allowing userspace to filter it. Only apply the PMU event
> > filter to *programmed* event counters.
>
> But that's a change in ABI, isn't it? We explicitly say in the
> documentation that the cycle counter can be filtered by specifying
> event 0x11.
Yeah... A bit of a dirty shortcut I took because I don't like the ABI,
but distaste isn't enough to break it :)
> More importantly, the current filtering works in terms of events, and
> not in terms of counters.
>
> Instead of changing the ABI, how about simply not supporting filtering
> on such non-compliant HW? Surely that would simplify a few things.
Yeah, that sounds reasonable. Especially if we allow programmable event
counters where the event ID space doesn't match the architecture.
--
Thanks,
Oliver
next prev parent reply other threads:[~2024-12-03 22:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-03 19:32 [RFC PATCH 00/14] KVM: arm64: Support FEAT_PMUv3 on Apple hardware Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 01/14] drivers/perf: apple_m1: Refactor event select/filter configuration Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 02/14] drivers/perf: apple_m1: Support host/guest event filtering Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 03/14] drivers/perf: apple_m1: Map generic branch events Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 04/14] KVM: arm64: Compute PMCEID from arm_pmu's event bitmaps Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 05/14] KVM: arm64: Always allow fixed cycle counter Oliver Upton
2024-12-03 21:32 ` Marc Zyngier
2024-12-03 22:32 ` Oliver Upton [this message]
2024-12-04 9:04 ` Marc Zyngier
2024-12-04 21:56 ` Oliver Upton
2024-12-10 9:49 ` Marc Zyngier
2024-12-03 19:32 ` [RFC PATCH 06/14] KVM: arm64: Use PERF_COUNT_HW_CPU_CYCLES for " Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 07/14] KVM: arm64: Use a cpucap to determine if system supports FEAT_PMUv3 Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 08/14] KVM: arm64: Drop kvm_arm_pmu_available static key Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 09/14] KVM: arm64: Use guard() to cleanup usage of arm_pmus_lock Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 10/14] KVM: arm64: Move PMUVer filtering into KVM code Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 11/14] KVM: arm64: Compute synthetic sysreg ESR for Apple PMUv3 traps Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 12/14] KVM: arm64: Advertise PMUv3 if IMPDEF traps are present Oliver Upton
2024-12-03 19:32 ` [RFC PATCH 13/14] KVM: arm64: Advertise 0 event counters for IMPDEF PMU Oliver Upton
2024-12-03 19:34 ` [RFC PATCH 14/14] arm64: Enable IMP DEF PMUv3 traps on Apple M2 Oliver Upton
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