From: Oliver Upton <oliver.upton@linux.dev>
To: Raghavendra Rao Ananta <rananta@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
Alexandru Elisei <alexandru.elisei@arm.com>,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Shaoqin Huang <shahuang@redhat.com>,
Jing Zhang <jingzhangos@google.com>,
Reiji Watanabe <reijiw@google.com>,
Colton Lewis <coltonlewis@google.com>,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v5 02/12] KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset
Date: Mon, 18 Sep 2023 09:47:27 -0700 [thread overview]
Message-ID: <ZQh/H5aMoqpYgVZg@linux.dev> (raw)
In-Reply-To: <CAJHc60ytL7T73wwabD8C2+RkVgN3OQsNuBwdQKz+Qen9b_hq9A@mail.gmail.com>
On Mon, Sep 18, 2023 at 09:41:02AM -0700, Raghavendra Rao Ananta wrote:
> On Fri, Sep 15, 2023 at 12:33 PM Oliver Upton <oliver.upton@linux.dev> wrote:
[...]
> > This would eliminate the possibility of returning ENODEV to userspace
> > where we shouldn't.
> >
> I understand that we'll be breaking the API contract and userspace may
> have to adapt to this change, but is it not acceptable to document and
> return ENODEV, since ENODEV may offer more clarity to userspace as to
> why the ioctl failed? In general, do we never extend the APIs?
Yes, we extend the existing interfaces all the time, but we almost
always require user opt in for user-visible changes in behavior. Look at
the way arm64_check_features() is handled -- we hide the 'detailed'
error and return EINVAL due to UAPI.
--
Thanks,
Oliver
next prev parent reply other threads:[~2023-09-18 16:48 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-17 0:30 [PATCH v5 00/12] KVM: arm64: PMU: Allow userspace to limit the number of PMCs on vCPU Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 01/12] KVM: arm64: PMU: Introduce a helper to set the guest's PMU Raghavendra Rao Ananta
2023-09-15 19:22 ` Oliver Upton
2023-09-18 17:24 ` Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 02/12] KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset Raghavendra Rao Ananta
2023-08-17 5:03 ` kernel test robot
2023-08-17 7:54 ` kernel test robot
2023-09-15 19:33 ` Oliver Upton
2023-09-18 16:41 ` Raghavendra Rao Ananta
2023-09-18 16:47 ` Oliver Upton [this message]
2023-09-18 16:58 ` Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 03/12] KVM: arm64: PMU: Clear PM{C,I}NTEN{SET,CLR} and PMOVS{SET,CLR} " Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 04/12] KVM: arm64: PMU: Don't define the sysreg reset() for PM{USERENR,CCFILTR}_EL0 Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 05/12] KVM: arm64: PMU: Simplify extracting PMCR_EL0.N Raghavendra Rao Ananta
2023-08-17 6:38 ` kernel test robot
2023-09-15 19:56 ` Oliver Upton
2023-09-18 16:53 ` Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 06/12] KVM: arm64: PMU: Add a helper to read a vCPU's PMCR_EL0 Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 07/12] KVM: arm64: PMU: Set PMCR_EL0.N for vCPU based on the associated PMU Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 08/12] KVM: arm64: PMU: Allow userspace to limit PMCR_EL0.N for the guest Raghavendra Rao Ananta
2023-08-21 12:12 ` Shaoqin Huang
2023-08-21 23:28 ` Raghavendra Rao Ananta
2023-08-22 3:26 ` Shaoqin Huang
2023-09-15 20:36 ` Oliver Upton
2023-09-18 17:02 ` Raghavendra Rao Ananta
2023-08-22 10:05 ` Shaoqin Huang
2023-08-23 16:06 ` Raghavendra Rao Ananta
2023-08-24 8:50 ` Shaoqin Huang
2023-08-25 22:34 ` Raghavendra Rao Ananta
2023-08-26 2:40 ` Shaoqin Huang
2023-09-15 20:53 ` Oliver Upton
2023-09-15 21:54 ` Oliver Upton
2023-09-18 17:11 ` Raghavendra Rao Ananta
2023-09-18 17:22 ` Raghavendra Rao Ananta
2023-09-18 17:07 ` Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 09/12] tools: Import arm_pmuv3.h Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 10/12] KVM: selftests: aarch64: Introduce vpmu_counter_access test Raghavendra Rao Ananta
2023-09-15 21:00 ` Oliver Upton
2023-09-18 17:20 ` Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 11/12] KVM: selftests: aarch64: vPMU register test for implemented counters Raghavendra Rao Ananta
2023-08-17 0:30 ` [PATCH v5 12/12] KVM: selftests: aarch64: vPMU register test for unimplemented counters Raghavendra Rao Ananta
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