From: Oliver Upton <oliver.upton@linux.dev>
To: Reiji Watanabe <reijiw@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
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>,
Zenghui Yu <yuzenghui@huawei.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Jing Zhang <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>
Subject: Re: [PATCH v2 2/5] KVM: arm64: PMU: Disallow vPMU on non-uniform PMUVer systems
Date: Mon, 31 Jul 2023 09:41:02 -0700 [thread overview]
Message-ID: <ZMfkHrRNGNA7XLso@linux.dev> (raw)
In-Reply-To: <CAAeT=FyC42s=kcS3QTC6A-s6EZjhoQL7XJyxWCb5YyisJrQvdg@mail.gmail.com>
On Mon, Jul 31, 2023 at 04:54:04AM -0700, Reiji Watanabe wrote:
> Hi Oliver,
>
> > This doesn't actually disallow userspace from configuring a vPMU, it
> > only hides the KVM cap. kvm_host_pmu_init() will still insert the host
> > PMU instance in the list of valid PMUs, and there doesn't appear to be
> > any check against the static key anywhere on that path.
>
> In v6.5-rc3, which I used as the base, or even in v6.5-rc4,
> it appears kvm_reset_vcpu() checks against the static key.
> So, the initial KVM_ARM_VCPU_INIT with vPMU configured will
> fail on the systems. Or am I missing something ? (Or is that
> going to be removed by other patches that are already queued?)
No, I definitely missed something, sorry for the noise! I had only
checked the PMU attributes, forgot about feature flags for a moment.
> > I actually prefer where we flip the static key, as PMU context switching
> > depends on both KVM support as well as the PMU driver coming up successfully.
> > Instead, you could hoist the check against the sanitised PMU version into
> > kvm_host_pmu_init(), maybe something like:
>
> Thank you, it looks better. I will fix this in v3.
Sounds good, thanks!
--
Best,
Oliver
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next prev parent reply other threads:[~2023-07-31 16:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-28 18:19 [PATCH v2 0/5] KVM: arm64: PMU: Fix PMUver related handling for vPMU support Reiji Watanabe
2023-07-28 18:19 ` [PATCH v2 1/5] KVM: arm64: PMU: Use of pmuv3_implemented() instead of open-coded version Reiji Watanabe
2023-07-28 18:19 ` [PATCH v2 2/5] KVM: arm64: PMU: Disallow vPMU on non-uniform PMUVer systems Reiji Watanabe
2023-07-28 19:52 ` Oliver Upton
2023-07-31 11:54 ` Reiji Watanabe
2023-07-31 16:41 ` Oliver Upton [this message]
2023-07-28 18:19 ` [PATCH v2 3/5] KVM: arm64: PMU: Avoid inappropriate use of host's PMUVer Reiji Watanabe
2023-07-28 18:19 ` [PATCH v2 4/5] KVM: arm64: PMU: Don't advertise the STALL_SLOT event Reiji Watanabe
2023-07-28 18:19 ` [PATCH v2 5/5] KVM: arm64: PMU: Don't advertise STALL_SLOT_{FRONTEND,BACKEND} Reiji Watanabe
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