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From: Marc Zyngier <maz@kernel.org>
To: Fuad Tabba <tabba@google.com>
Cc: kernel-team@android.com, catalin.marinas@arm.com,
	will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 3/4] KVM: arm64: Pass pmu events to hyp via vcpu
Date: Mon, 09 May 2022 11:41:22 +0100	[thread overview]
Message-ID: <87ee136l9p.wl-maz@kernel.org> (raw)
In-Reply-To: <20220509095500.2408785-4-tabba@google.com>

On Mon, 09 May 2022 10:54:59 +0100,
Fuad Tabba <tabba@google.com> wrote:
> 
> Instead of the host accessing hyp data directly, pass the pmu
> events of the current cpu to hyp via the vcpu.
> 
> This adds 64 bits (in two fields) to the vcpu that need to be
> synced before every vcpu run in nvhe and protected modes.
> However, it isolates the hypervisor from the host, which allows
> us to use pmu in protected mode in a subsequent patch.
> 
> No functional change intended.

BTW, there *are* plenty of functional changes, even if there was no
issue with the patch. The lifetime of the data structure changes, its
sharing changes, and its memory footprint is different.

I guess what you are trying to say is that there shouldn't be any
visible side effect of this patch. But I don't think these are the
same things.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Fuad Tabba <tabba@google.com>
Cc: kvmarm@lists.cs.columbia.edu, will@kernel.org,
	qperret@google.com, james.morse@arm.com,
	alexandru.elisei@arm.com, suzuki.poulose@arm.com,
	catalin.marinas@arm.com, drjones@redhat.com,
	linux-arm-kernel@lists.infradead.org, kernel-team@android.com
Subject: Re: [PATCH v2 3/4] KVM: arm64: Pass pmu events to hyp via vcpu
Date: Mon, 09 May 2022 11:41:22 +0100	[thread overview]
Message-ID: <87ee136l9p.wl-maz@kernel.org> (raw)
In-Reply-To: <20220509095500.2408785-4-tabba@google.com>

On Mon, 09 May 2022 10:54:59 +0100,
Fuad Tabba <tabba@google.com> wrote:
> 
> Instead of the host accessing hyp data directly, pass the pmu
> events of the current cpu to hyp via the vcpu.
> 
> This adds 64 bits (in two fields) to the vcpu that need to be
> synced before every vcpu run in nvhe and protected modes.
> However, it isolates the hypervisor from the host, which allows
> us to use pmu in protected mode in a subsequent patch.
> 
> No functional change intended.

BTW, there *are* plenty of functional changes, even if there was no
issue with the patch. The lifetime of the data structure changes, its
sharing changes, and its memory footprint is different.

I guess what you are trying to say is that there shouldn't be any
visible side effect of this patch. But I don't think these are the
same things.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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

  parent reply	other threads:[~2022-05-09 10:41 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-09  9:54 [PATCH v2 0/4] KVM: arm64: Do not communicate host pmu event changes by accessing hyp data Fuad Tabba
2022-05-09  9:54 ` Fuad Tabba
2022-05-09  9:54 ` [PATCH v2 1/4] KVM: arm64: Wrapper for getting pmu_events Fuad Tabba
2022-05-09  9:54   ` Fuad Tabba
2022-05-09  9:54 ` [PATCH v2 2/4] KVM: arm64: Repack struct kvm_pmu to reduce size Fuad Tabba
2022-05-09  9:54   ` Fuad Tabba
2022-05-09  9:54 ` [PATCH v2 3/4] KVM: arm64: Pass pmu events to hyp via vcpu Fuad Tabba
2022-05-09  9:54   ` Fuad Tabba
2022-05-09 10:31   ` Marc Zyngier
2022-05-09 10:31     ` Marc Zyngier
2022-05-09 10:47     ` Fuad Tabba
2022-05-09 10:47       ` Fuad Tabba
2022-05-09 10:41   ` Marc Zyngier [this message]
2022-05-09 10:41     ` Marc Zyngier
2022-05-09 10:48     ` Fuad Tabba
2022-05-09 10:48       ` Fuad Tabba
2022-05-09  9:55 ` [PATCH v2 4/4] KVM: arm64: Reenable pmu in Protected Mode Fuad Tabba
2022-05-09  9:55   ` Fuad Tabba

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