Subject: [PATCH 10/10] KVM: arm/arm64: vgic: Allow non-shared device HW interrupts

From: [email-masked] (Eric Auger)
Date: Wed, 17 Jun 2015 17:11:02 +0200

Hi Marc,
On 06/08/2015 07:04 PM, Marc Zyngier wrote:
> So far, the only use of the HW interrupt facility is the timer,
> implying that the active state is context-switched for each vcpu,
> as the device is is shared across all vcpus.
s/is//
> 
> This does not work for a device that has been assigned to a VM,
> as the guest is entierely in control of that device (the HW is
entirely?
> not shared). In that case, it makes sense to bypass the whole
> active state srtwitchint, and only track the deactivation of the
switching
> interrupt.
> 
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
>  include/kvm/arm_vgic.h    |  5 +++--
>  virt/kvm/arm/arch_timer.c |  2 +-
>  virt/kvm/arm/vgic.c       | 37 ++++++++++++++++++++++++-------------
>  3 files changed, 28 insertions(+), 16 deletions(-)
> 
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 1c653c1..5d47d60 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -164,7 +164,8 @@ struct irq_phys_map {
>  	u32			virt_irq;
>  	u32			phys_irq;
>  	u32			irq;
> -	bool			active;
> +	bool			shared;
> +	bool			active; /* Only valid if shared */
>  };
>  
>  struct vgic_dist {
> @@ -347,7 +348,7 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
>  int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
>  int kvm_vgic_vcpu_active_irq(struct kvm_vcpu *vcpu);
>  struct irq_phys_map *vgic_map_phys_irq(struct kvm_vcpu *vcpu,
> -				       int virt_irq, int irq);
> +				       int virt_irq, int irq, bool shared);
>  int vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, struct irq_phys_map *map);
>  bool vgic_get_phys_irq_active(struct irq_phys_map *map);
>  void vgic_set_phys_irq_active(struct irq_phys_map *map, bool active);
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index b9fff78..9544d79 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -202,7 +202,7 @@ void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
>  	 * Tell the VGIC that the virtual interrupt is tied to a
>  	 * physical interrupt. We do that once per VCPU.
>  	 */
> -	timer->map = vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
> +	timer->map = vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq, true);
>  	WARN_ON(!timer->map);
>  }
>  
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index f376b56..4223166 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -1125,18 +1125,21 @@ static void vgic_queue_irq_to_lr(struct kvm_vcpu *vcpu, int irq,
>  		map = vgic_irq_map_search(vcpu, irq);
>  
>  		if (map) {
> -			int ret;
> -
> -			BUG_ON(!map->active);
>  			vlr.hwirq = map->phys_irq;
>  			vlr.state |= LR_HW;
>  			vlr.state &= ~LR_EOI_INT;
>  
> -			ret = irq_set_irqchip_state(map->irq,
> -						    IRQCHIP_STATE_ACTIVE,
> -						    true);
>  			vgic_irq_set_queued(vcpu, irq);
the queued state is set again in vgic_queue_hwirq for level_sensitive
IRQs although not harmful.
> -			WARN_ON(ret);
> +
> +			if (map->shared) {
> +				int ret;
> +
> +				BUG_ON(!map->active);
> +				ret = irq_set_irqchip_state(map->irq,
> +							    IRQCHIP_STATE_ACTIVE,
> +							    true);
> +				WARN_ON(ret);
> +			}
>  		}
>  	}
>  
> @@ -1368,21 +1371,28 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu)
>  static int vgic_sync_hwirq(struct kvm_vcpu *vcpu, struct vgic_lr vlr)
>  {
>  	struct irq_phys_map *map;
> +	bool active;
>  	int ret;
>  
>  	if (!(vlr.state & LR_HW))
>  		return 0;
>  
>  	map = vgic_irq_map_search(vcpu, vlr.irq);
> -	BUG_ON(!map || !map->active);
> +	BUG_ON(!map);
> +	BUG_ON(map->shared && !map->active);
>  
>  	ret = irq_get_irqchip_state(map->irq,
>  				    IRQCHIP_STATE_ACTIVE,
> -				    &map->active);
> +				    &active);
>  
In case of non shared and EOIMode = 1 - I know this is not your current
interest here though ;-) - , once the guest EOIs its virtual IRQ and GIC
deactivates the physical one, a new phys IRQ can hit immediatly, the
physical handler can be entered and the state is seen as active here.
The queued state is never reset in such a case and the system gets stuck
since the can_sample fails I think. What I mean here is sounds the state
machine as is does not work for my VFIO case. So some adaptations still
are needed I think. Do you share my diagnosis?

Eric
>  
> -	if (map->active) {
> +	if (!map->shared)
> +		return !active;
> +
> +	map->active = active;
> +
> +	if (active) {
>  		ret = irq_set_irqchip_state(map->irq,
>  					    IRQCHIP_STATE_ACTIVE,
>  					    false);
> @@ -1663,7 +1673,7 @@ static struct rb_root *vgic_get_irq_phys_map(struct kvm_vcpu *vcpu,
>  }
>  
>  struct irq_phys_map *vgic_map_phys_irq(struct kvm_vcpu *vcpu,
> -				       int virt_irq, int irq)
> +				       int virt_irq, int irq, bool shared)
>  {
>  	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>  	struct rb_root *root = vgic_get_irq_phys_map(vcpu, virt_irq);
> @@ -1710,6 +1720,7 @@ struct irq_phys_map *vgic_map_phys_irq(struct kvm_vcpu *vcpu,
>  	new_map->virt_irq = virt_irq;
>  	new_map->phys_irq = phys_irq;
>  	new_map->irq = irq;
> +	new_map->shared = shared;
>  
>  	rb_link_node(&new_map->node, parent, new);
>  	rb_insert_color(&new_map->node, root);
> @@ -1746,13 +1757,13 @@ static struct irq_phys_map *vgic_irq_map_search(struct kvm_vcpu *vcpu,
>  
>  bool vgic_get_phys_irq_active(struct irq_phys_map *map)
>  {
> -	BUG_ON(!map);
> +	BUG_ON(!map || !map->shared);
>  	return map->active;
>  }
>  
>  void vgic_set_phys_irq_active(struct irq_phys_map *map, bool active)
>  {
> -	BUG_ON(!map);
> +	BUG_ON(!map || !map->shared);
>  	map->active = active;
>  }
>  
>