Re: [PATCH 08/10] KVM: arm/arm64: vgic: Handle unshared mapped interrupts

[Marc Zyngier]

On Wed, May 24 2017 at 10:13:21 pm BST, Eric Auger <eric.auger@xxxxxxxxxx> wrote:
> Virtual interrupts directly mapped to physical interrupts require
> some special care. Their pending and active state must be observed
> at distributor level and not in the list register.
>
> Also a level sensitive interrupt's level is not toggled down by any
> maintenance IRQ handler as the EOI is not trapped.
>
> This patch adds an host_irq field in vgic_irq struct to easily
> get the irqchip state of the host irq. We also handle the
> physical IRQ case in vgic_validate_injection and add helpers to
> get the line level and active state.
>
> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
> ---
>  include/kvm/arm_vgic.h    |  4 +++-
>  virt/kvm/arm/arch_timer.c |  3 ++-
>  virt/kvm/arm/vgic/vgic.c  | 44 ++++++++++++++++++++++++++++++++++++++------
>  virt/kvm/arm/vgic/vgic.h  |  9 ++++++++-
>  4 files changed, 51 insertions(+), 9 deletions(-)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index ef71858..695ebc7 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -112,6 +112,7 @@ struct vgic_irq {
>  	bool hw;			/* Tied to HW IRQ */
>  	struct kref refcount;		/* Used for LPIs */
>  	u32 hwintid;			/* HW INTID number */
> +	unsigned int host_irq;		/* linux irq corresponding to hwintid */
>  	union {
>  		u8 targets;			/* GICv2 target VCPUs mask */
>  		u32 mpidr;			/* GICv3 target VCPU */
> @@ -301,7 +302,8 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
>  			bool level);
>  int kvm_vgic_inject_mapped_irq(struct kvm *kvm, int cpuid, unsigned int intid,
>  			       bool level);
> -int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, u32 virt_irq, u32 phys_irq);
> +int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
> +			  u32 virt_irq, u32 phys_irq);
>  int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int virt_irq);
>  bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int virt_irq);
>  
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 5976609..45f4779 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -651,7 +651,8 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  	 * Tell the VGIC that the virtual interrupt is tied to a
>  	 * physical interrupt. We do that once per VCPU.
>  	 */
> -	ret = kvm_vgic_map_phys_irq(vcpu, vtimer->irq.irq, phys_irq);
> +	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq,
> +				    vtimer->irq.irq, phys_irq);
>  	if (ret)
>  		return ret;
>  
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index 83b24d2..aa0618c 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -137,6 +137,28 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
>  	kfree(irq);
>  }
>  
> +bool irq_line_level(struct vgic_irq *irq)
> +{
> +	bool line_level = irq->line_level;
> +
> +	if (unlikely(is_unshared_mapped(irq)))

The "unshared" bit doesn't mean much to me. Do you want to say "an
interrupt that belongs to a device only accessed by a single VM"?

Given that this can only be an SPI, can we use something like
"is_mapped_spi()" instead? I find it a lot more readable, but I'm open
to alternative suggestions.

> +		WARN_ON(irq_get_irqchip_state(irq->host_irq,
> +					      IRQCHIP_STATE_PENDING,
> +					      &line_level));
> +	return line_level;
> +}
> +
> +bool irq_is_active(struct vgic_irq *irq)
> +{
> +	bool is_active = irq->active;
> +
> +	if (unlikely(is_unshared_mapped(irq)))
> +		WARN_ON(irq_get_irqchip_state(irq->host_irq,
> +					      IRQCHIP_STATE_ACTIVE,
> +					      &is_active));
> +	return is_active;
> +}
> +
>  /**
>   * kvm_vgic_target_oracle - compute the target vcpu for an irq
>   *
> @@ -153,7 +175,7 @@ static struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
>  	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));
>  
>  	/* If the interrupt is active, it must stay on the current vcpu */
> -	if (irq->active)
> +	if (irq_is_active(irq))
>  		return irq->vcpu ? : irq->target_vcpu;
>  
>  	/*
> @@ -195,14 +217,18 @@ static int vgic_irq_cmp(void *priv, struct list_head *a, struct list_head *b)
>  {
>  	struct vgic_irq *irqa = container_of(a, struct vgic_irq, ap_list);
>  	struct vgic_irq *irqb = container_of(b, struct vgic_irq, ap_list);
> +	bool activea, activeb;
>  	bool penda, pendb;
>  	int ret;
>  
>  	spin_lock(&irqa->irq_lock);
>  	spin_lock_nested(&irqb->irq_lock, SINGLE_DEPTH_NESTING);
>  
> -	if (irqa->active || irqb->active) {
> -		ret = (int)irqb->active - (int)irqa->active;
> +	activea = irq_is_active(irqa);
> +	activeb = irq_is_active(irqb);
> +
> +	if (activea || activeb) {
> +		ret = (int)activeb - (int)activea;
>  		goto out;
>  	}
>  
> @@ -234,13 +260,17 @@ static void vgic_sort_ap_list(struct kvm_vcpu *vcpu)
>  
>  /*
>   * Only valid injection if changing level for level-triggered IRQs or for a
> - * rising edge.
> + * rising edge. Injection of virtual interrupts associated to physical
> + * interrupts always is valid.
>   */
>  static bool vgic_validate_injection(struct vgic_irq *irq, bool level)
>  {
>  	switch (irq->config) {
>  	case VGIC_CONFIG_LEVEL:
> -		return irq->line_level != level;
> +		if (unlikely(is_unshared_mapped(irq)))
> +			return true;
> +		else
> +			return irq->line_level != level;

This would be more readable as:

		return (irq->line_level != level ||
                	unlikely(is_unshared_mapped(irq)));

>  	case VGIC_CONFIG_EDGE:
>  		return level;
>  	}
> @@ -392,7 +422,8 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
>  	return 0;
>  }
>  
> -int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, u32 virt_irq, u32 phys_irq)
> +int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
> +			  u32 virt_irq, u32 phys_irq)
>  {
>  	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, virt_irq);
>  
> @@ -402,6 +433,7 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, u32 virt_irq, u32 phys_irq)
>  
>  	irq->hw = true;
>  	irq->hwintid = phys_irq;
> +	irq->host_irq = host_irq;

If you're now passing the Linux IRQ to the mapping function, you might
as well move the code that extracts the host hwirq here as well.

>  
>  	spin_unlock(&irq->irq_lock);
>  	vgic_put_irq(vcpu->kvm, irq);
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index da83e4c..dc4972b 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -17,6 +17,7 @@
>  #define __KVM_ARM_VGIC_NEW_H__
>  
>  #include <linux/irqchip/arm-gic-common.h>
> +#include <linux/interrupt.h>
>  
>  #define PRODUCT_ID_KVM		0x4b	/* ASCII code K */
>  #define IMPLEMENTER_ARM		0x43b
> @@ -96,14 +97,20 @@
>  /* we only support 64 kB translation table page size */
>  #define KVM_ITS_L1E_ADDR_MASK		GENMASK_ULL(51, 16)
>  
> +bool irq_line_level(struct vgic_irq *irq);
> +bool irq_is_active(struct vgic_irq *irq);
> +
>  static inline bool irq_is_pending(struct vgic_irq *irq)
>  {
>  	if (irq->config == VGIC_CONFIG_EDGE)
>  		return irq->pending_latch;
>  	else
> -		return irq->pending_latch || irq->line_level;
> +		return irq->pending_latch || irq_line_level(irq);
>  }
>  
> +#define is_unshared_mapped(i) \
> +((i)->hw && (i)->intid >= VGIC_NR_PRIVATE_IRQS && (i)->intid < 1020)
> +
>  /*
>   * This struct provides an intermediate representation of the fields contained
>   * in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC

Thanks,

	M.
-- 
Jazz is not dead, it just smell funny.