linux-kernel - Re: [PATCH v5 19/23] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts

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Date:   Thu, 19 Mar 2020 17:16:36 +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 19/23] KVM: arm64: GICv4.1: Allow SGIs to switch
 between HW and SW interrupts

Hi Marc,

On 3/4/20 9:33 PM, Marc Zyngier wrote:
> In order to let a guest buy in the new, active-less SGIs, we
> need to be able to switch between the two modes.
> 
> Handle this by stopping all guest activity, transfer the state
> from one mode to the other, and resume the guest. Nothing calls
> this code so far, but a later patch will plug it into the MMIO
> emulation.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  include/kvm/arm_vgic.h      |  3 ++
>  virt/kvm/arm/vgic/vgic-v4.c | 94 +++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/vgic/vgic.h    |  1 +
>  3 files changed, 98 insertions(+)
> 
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 63457908c9c4..69f4164d6477 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -231,6 +231,9 @@ struct vgic_dist {
>  	/* distributor enabled */
>  	bool			enabled;
>  
> +	/* Wants SGIs without active state */
> +	bool			nassgireq;
> +
>  	struct vgic_irq		*spis;
>  
>  	struct vgic_io_device	dist_iodev;
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index c2fcde104ea2..a65dc1c85363 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -97,6 +97,100 @@ static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
>  	return IRQ_HANDLED;
>  }
>  
> +static void vgic_v4_sync_sgi_config(struct its_vpe *vpe, struct vgic_irq *irq)
> +{
> +	vpe->sgi_config[irq->intid].enabled	= irq->enabled;
> +	vpe->sgi_config[irq->intid].group 	= irq->group;
> +	vpe->sgi_config[irq->intid].priority	= irq->priority;
> +}
> +
> +static void vgic_v4_enable_vsgis(struct kvm_vcpu *vcpu)
> +{
> +	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
> +	int i;
> +
> +	/*
> +	 * With GICv4.1, every virtual SGI can be directly injected. So
> +	 * let's pretend that they are HW interrupts, tied to a host
> +	 * IRQ. The SGI code will do its magic.
> +	 */
> +	for (i = 0; i < VGIC_NR_SGIS; i++) {
> +		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
> +		struct irq_desc *desc;
> +		int ret;
Is is safe without holding the irq->irq_lock?
> +
> +		if (irq->hw) {
> +			vgic_put_irq(vcpu->kvm, irq);
> +			continue;
> +		}
> +
> +		irq->hw = true;
> +		irq->host_irq = irq_find_mapping(vpe->sgi_domain, i);
> +
> +		/* Transfer the full irq state to the vPE */
> +		vgic_v4_sync_sgi_config(vpe, irq);
> +		desc = irq_to_desc(irq->host_irq);
> +		ret = irq_domain_activate_irq(irq_desc_get_irq_data(desc),
> +					      false);
> +		if (!WARN_ON(ret)) {
> +			/* Transfer pending state */
> +			ret = irq_set_irqchip_state(irq->host_irq,
> +						    IRQCHIP_STATE_PENDING,
> +						    irq->pending_latch);
> +			WARN_ON(ret);
> +			irq->pending_latch = false;
> +		}
> +
> +		vgic_put_irq(vcpu->kvm, irq);
> +	}
> +}
> +
> +static void vgic_v4_disable_vsgis(struct kvm_vcpu *vcpu)
> +{
> +	int i;
> +
> +	for (i = 0; i < VGIC_NR_SGIS; i++) {
> +		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
> +		struct irq_desc *desc;
> +		int ret;
> +
> +		if (!irq->hw) {
> +			vgic_put_irq(vcpu->kvm, irq);
> +			continue;
> +		}
> +
> +		irq->hw = false;
> +		ret = irq_get_irqchip_state(irq->host_irq,
> +					    IRQCHIP_STATE_PENDING,
> +					    &irq->pending_latch);
> +		WARN_ON(ret);
> +
> +		desc = irq_to_desc(irq->host_irq);
> +		irq_domain_deactivate_irq(irq_desc_get_irq_data(desc));
> +
> +		vgic_put_irq(vcpu->kvm, irq);
> +	}
> +}
> +
> +/* Must be called with the kvm lock held */
> +void vgic_v4_configure_vsgis(struct kvm *kvm)
> +{
> +	struct vgic_dist *dist = &kvm->arch.vgic;
> +	struct kvm_vcpu *vcpu;
> +	int i;
> +
> +	kvm_arm_halt_guest(kvm);
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		if (dist->nassgireq)
> +			vgic_v4_enable_vsgis(vcpu);
> +		else
> +			vgic_v4_disable_vsgis(vcpu);
> +	}
> +
> +	kvm_arm_resume_guest(kvm);
> +}
> +
>  /**
>   * vgic_v4_init - Initialize the GICv4 data structures
>   * @kvm:	Pointer to the VM being initialized
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index c7fefd6b1c80..769e4802645e 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -316,5 +316,6 @@ void vgic_its_invalidate_cache(struct kvm *kvm);
>  bool vgic_supports_direct_msis(struct kvm *kvm);
>  int vgic_v4_init(struct kvm *kvm);
>  void vgic_v4_teardown(struct kvm *kvm);
> +void vgic_v4_configure_vsgis(struct kvm *kvm);
>  
>  #endif
> 
Thanks

Eric