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From: Oliver Upton <oupton@google.com>
To: Fuad Tabba <tabba@google.com>
Cc: will@kernel.org, maz@kernel.org, catalin.marinas@arm.com,
	kernel-team@android.com, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 4/4] KVM: arm64: Reenable pmu in Protected Mode
Date: Mon, 9 May 2022 22:36:00 +0000	[thread overview]
Message-ID: <YnmXULIsOO27g/8N@google.com> (raw)
In-Reply-To: <20220509120330.3043773-5-tabba@google.com>

Hi Fuad,

On Mon, May 09, 2022 at 12:03:30PM +0000, Fuad Tabba wrote:
> Now that the pmu code does not access hyp data, reenable it in
> protected mode.
> 
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>  arch/arm64/kvm/pmu-emul.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> index 3dc990ac4f44..11c43bed5f97 100644
> --- a/arch/arm64/kvm/pmu-emul.c
> +++ b/arch/arm64/kvm/pmu-emul.c
> @@ -774,8 +774,7 @@ void kvm_host_pmu_init(struct arm_pmu *pmu)
>  {
>  	struct arm_pmu_entry *entry;
>  
> -	if (pmu->pmuver == 0 || pmu->pmuver == ID_AA64DFR0_PMUVER_IMP_DEF ||
> -	    is_protected_kvm_enabled())
> +	if (pmu->pmuver == 0 || pmu->pmuver == ID_AA64DFR0_PMUVER_IMP_DEF)

IIUC, you intend to enable the PMU for non-pVM guests, right? Based on
the pKVM feature registers + trap handlers I can see that pVM use of the
PMU is in fact disabled. It'd be good to state in the commit message
what is exactly intended for pVMs and non-pVMs.

Since the PMU counters are disabled outright for pVMs, is there any
value in context switching between host/guest in this case?

--
Thanks,
Oliver
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  reply	other threads:[~2022-05-09 22:36 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-09 12:03 [PATCH v3 0/4] KVM: arm64: Do not communicate host pmu event changes by accessing hyp data Fuad Tabba
2022-05-09 12:03 ` [PATCH v3 1/4] KVM: arm64: Wrapper for getting pmu_events Fuad Tabba
2022-05-09 19:41   ` Oliver Upton
2022-05-09 12:03 ` [PATCH v3 2/4] KVM: arm64: Repack struct kvm_pmu to reduce size Fuad Tabba
2022-05-09 19:57   ` Oliver Upton
2022-05-10  6:38     ` Fuad Tabba
2022-05-09 12:03 ` [PATCH v3 3/4] KVM: arm64: Pass pmu events to hyp via vcpu Fuad Tabba
2022-05-09 20:21   ` Oliver Upton
2022-05-10  6:43     ` Fuad Tabba
2022-05-10  9:21       ` Marc Zyngier
2022-05-09 12:03 ` [PATCH v3 4/4] KVM: arm64: Reenable pmu in Protected Mode Fuad Tabba
2022-05-09 22:36   ` Oliver Upton [this message]
2022-05-10  6:45     ` Fuad Tabba

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