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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 1/1] KVM: arm64: PMU: Avoid inappropriate use of host's
 PMUVer
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On Mon, Jun 12, 2023 at 05:26:33PM -0700, Reiji Watanabe wrote:
> On Mon, Jun 12, 2023 at 09:36:38PM +0200, Oliver Upton wrote:
> > I'd rather we start exposing the feature when we provide all the
> > necessary detail.
> 
> To confirm, are you suggesting to stop exposing the event even on hosts
> w/o PMMIR_EL1 until KVM gets ready to support PMMIR_EL1 ?
> (guests on those hosts won't get PMMIR_EL1 in any case though?)
> Could you please explain why ?
> 
> Perhaps I think I would rather keep the code as it is?
> (since I'm simply not sure what would be the benefits of that)

I'd rather not keep confusing code hanging around. The fact that KVM
does not support the STALL_SLOTS event is invariant of both the hardware
PMU implementation and the userspace value for the ID register field.
Let's make sure the implementation exactly matches this position.

-- 
Thanks,
Oliver