linux-kernel - Re: [PATCH v5 17/23] KVM: arm64: GICv4.1: Let doorbells be auto-enabled

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Message-ID: <43848b89-29fe-eb34-b6d9-f9723f40a8f1@redhat.com>
Date:   Tue, 17 Mar 2020 12:04:22 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Zenghui Yu <yuzenghui@...wei.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH v5 17/23] KVM: arm64: GICv4.1: Let doorbells be
 auto-enabled

Hi Marc,

On 3/4/20 9:33 PM, Marc Zyngier wrote:
> As GICv4.1 understands the life cycle of doorbells (instead of
> just randomly firing them at the most inconvenient time), just
> enable them at irq_request time, and be done with it.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Eric

> ---
>  virt/kvm/arm/vgic/vgic-v4.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index 1eb0f8c76219..c2fcde104ea2 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -141,6 +141,7 @@ int vgic_v4_init(struct kvm *kvm)
>  
>  	kvm_for_each_vcpu(i, vcpu, kvm) {
>  		int irq = dist->its_vm.vpes[i]->irq;
> +		unsigned long irq_flags = DB_IRQ_FLAGS;
>  
>  		/*
>  		 * Don't automatically enable the doorbell, as we're
> @@ -148,8 +149,14 @@ int vgic_v4_init(struct kvm *kvm)
>  		 * blocked. Also disable the lazy disabling, as the
>  		 * doorbell could kick us out of the guest too
>  		 * early...
> +		 *
> +		 * On GICv4.1, the doorbell is managed in HW and must
> +		 * be left enabled.
>  		 */
> -		irq_set_status_flags(irq, DB_IRQ_FLAGS);
> +		if (kvm_vgic_global_state.has_gicv4_1)
> +			irq_flags &= ~IRQ_NOAUTOEN;
> +		irq_set_status_flags(irq, irq_flags);
> +
>  		ret = request_irq(irq, vgic_v4_doorbell_handler,
>  				  0, "vcpu", vcpu);
>  		if (ret) {
>