From: Marc Zyngier <maz@kernel.org>
To: Colton Lewis <coltonlewis@google.com>
Cc: kvm@vger.kernel.org, Alexandru Elisei <alexandru.elisei@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Oliver Upton <oliver.upton@linux.dev>,
Mingwei Zhang <mizhang@google.com>,
Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Mark Rutland <mark.rutland@arm.com>,
Shuah Khan <shuah@kernel.org>,
Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
linux-perf-users@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v6 09/19] KVM: arm64: Write fast path PMU register handlers
Date: Thu, 12 Feb 2026 09:07:33 +0000 [thread overview]
Message-ID: <86ldgyba96.wl-maz@kernel.org> (raw)
In-Reply-To: <20260209221414.2169465-10-coltonlewis@google.com>
On Mon, 09 Feb 2026 22:14:04 +0000,
Colton Lewis <coltonlewis@google.com> wrote:
>
> We may want a partitioned PMU but not have FEAT_FGT to untrap the
> specific registers that would normally be untrapped. Add a handler for
> those registers in the fast path so we can still get a performance
> boost from partitioning.
>
> The idea is to handle traps for all the PMU registers quickly by
> writing directly to the hardware when possible instead of hooking into
> the emulated vPMU as the standard handlers in sys_regs.c do.
This seems extremely premature. My assumption is that PMU traps are
rare, and that doing a full exit should be acceptable. Until you
demonstrate the contrary, I don't want this sort of massive bloat in
the most performance-critical path.
"Start walking before you try to run".
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2026-02-12 9:07 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 22:13 [PATCH v6 00/19] ARM64 PMU Partitioning Colton Lewis
2026-02-09 22:13 ` [PATCH v6 01/19] arm64: cpufeature: Add cpucap for HPMN0 Colton Lewis
2026-02-09 22:13 ` [PATCH v6 02/19] KVM: arm64: Reorganize PMU includes Colton Lewis
2026-02-09 22:13 ` [PATCH v6 03/19] KVM: arm64: Reorganize PMU functions Colton Lewis
2026-02-09 22:13 ` [PATCH v6 04/19] perf: arm_pmuv3: Introduce method to partition the PMU Colton Lewis
2026-03-11 11:59 ` James Clark
2026-03-12 22:37 ` Colton Lewis
2026-03-11 17:45 ` James Clark
2026-03-12 22:37 ` Colton Lewis
2026-02-09 22:14 ` [PATCH v6 05/19] perf: arm_pmuv3: Generalize counter bitmasks Colton Lewis
2026-02-09 22:14 ` [PATCH v6 06/19] perf: arm_pmuv3: Keep out of guest counter partition Colton Lewis
2026-02-25 17:53 ` Colton Lewis
2026-03-11 12:00 ` James Clark
2026-03-12 22:39 ` Colton Lewis
2026-02-09 22:14 ` [PATCH v6 07/19] KVM: arm64: Set up FGT for Partitioned PMU Colton Lewis
2026-02-09 22:14 ` [PATCH v6 08/19] KVM: arm64: Define access helpers for PMUSERENR and PMSELR Colton Lewis
2026-02-10 4:30 ` kernel test robot
2026-02-10 5:20 ` kernel test robot
2026-02-09 22:14 ` [PATCH v6 09/19] KVM: arm64: Write fast path PMU register handlers Colton Lewis
2026-02-12 9:07 ` Marc Zyngier [this message]
2026-02-25 17:45 ` Colton Lewis
2026-02-09 22:14 ` [PATCH v6 10/19] KVM: arm64: Setup MDCR_EL2 to handle a partitioned PMU Colton Lewis
2026-02-09 22:14 ` [PATCH v6 11/19] KVM: arm64: Context swap Partitioned PMU guest registers Colton Lewis
2026-03-11 12:01 ` James Clark
2026-03-12 22:39 ` Colton Lewis
2026-02-09 22:14 ` [PATCH v6 12/19] KVM: arm64: Enforce PMU event filter at vcpu_load() Colton Lewis
2026-02-09 22:14 ` [PATCH v6 13/19] KVM: arm64: Implement lazy PMU context swaps Colton Lewis
2026-02-09 22:14 ` [PATCH v6 14/19] perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters Colton Lewis
2026-02-10 4:51 ` kernel test robot
2026-02-10 7:32 ` kernel test robot
2026-02-09 22:14 ` [PATCH v6 15/19] KVM: arm64: Detect overflows for the Partitioned PMU Colton Lewis
2026-02-09 22:14 ` [PATCH v6 16/19] KVM: arm64: Add vCPU device attr to partition the PMU Colton Lewis
2026-02-10 5:55 ` kernel test robot
2026-03-05 10:16 ` James Clark
2026-03-12 22:13 ` Colton Lewis
2026-02-09 22:14 ` [PATCH v6 17/19] KVM: selftests: Add find_bit to KVM library Colton Lewis
2026-02-09 22:14 ` [PATCH v6 18/19] KVM: arm64: selftests: Add test case for partitioned PMU Colton Lewis
2026-02-09 22:14 ` [PATCH v6 19/19] KVM: arm64: selftests: Relax testing for exceptions when partitioned Colton Lewis
2026-02-10 8:49 ` [PATCH v6 00/19] ARM64 PMU Partitioning Marc Zyngier
2026-02-12 21:08 ` Colton Lewis
2026-02-13 8:11 ` Marc Zyngier
2026-02-25 17:40 ` Colton Lewis
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