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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
Date: Wed, 14 Jun 2023 12:41:53 +0000	[thread overview]
Message-ID: <ZIm1kdFBfXYMdfbV@linux.dev> (raw)
In-Reply-To: <20230613002633.gdttlmn5bnkr4l5i@google.com>

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

WARNING: multiple messages have this Message-ID (diff)
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
Date: Wed, 14 Jun 2023 12:41:53 +0000	[thread overview]
Message-ID: <ZIm1kdFBfXYMdfbV@linux.dev> (raw)
In-Reply-To: <20230613002633.gdttlmn5bnkr4l5i@google.com>

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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2023-06-14 12:42 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-06-10 19:45 [PATCH 1/1] KVM: arm64: PMU: Avoid inappropriate use of host's PMUVer Reiji Watanabe
2023-06-11  0:57 ` Oliver Upton
2023-06-11  4:54   ` Reiji Watanabe
2023-06-11  7:47     ` Oliver Upton
2023-06-11 16:01       ` Reiji Watanabe
2023-06-12 19:36         ` Oliver Upton
2023-06-12 19:36           ` Oliver Upton
2023-06-13  0:26           ` Reiji Watanabe
2023-06-13  0:26             ` Reiji Watanabe
2023-06-14 12:41             ` Oliver Upton [this message]
2023-06-14 12:41               ` Oliver Upton

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