Subject: [PATCH 06/10] KVM: arm/arm64: vgic: Allow dynamic mapping of physical/virtual interrupts

From: [email-masked] (Andre Przywara)
Date: Thu, 11 Jun 2015 09:43:29 +0100

Hi,

On 06/08/2015 06:04 PM, Marc Zyngier wrote:
> In order to be able to feed physical interrupts to a guest, we need
> to be able to establish the virtual-physical mapping between the two
> worlds.
>
> The mapping is kept in a rbtree, indexed by virtual interrupts.
>
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
>  include/kvm/arm_vgic.h |  18 ++++++++
>  virt/kvm/arm/vgic.c    | 110 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 128 insertions(+)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 4f9fa1d..33d121a 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -159,6 +159,14 @@ struct vgic_io_device {
>       struct kvm_io_device dev;
>  };
>
> +struct irq_phys_map {
> +     struct rb_node          node;
> +     u32                     virt_irq;
> +     u32                     phys_irq;
> +     u32                     irq;

Can you add comments explaining the different IRQ types here?
So I take it that phys_irq is the actual SPI number (hwirq in irqchip
lingo), virt_irq is the guest's virtual IRQ number and irq is Linux'
notion of the IRQ number (the first column in /proc/interrupts)?
Would renaming help? (phys_irq to hwirq? virt_irq to guest_irq?)

> +     bool                    active;
> +};
> +
>  struct vgic_dist {
>       spinlock_t              lock;
>       bool                    in_kernel;
> @@ -256,6 +264,10 @@ struct vgic_dist {
>       struct vgic_vm_ops      vm_ops;
>       struct vgic_io_device   dist_iodev;
>       struct vgic_io_device   *redist_iodevs;
> +
> +     /* Virtual irq to hwirq mapping */
> +     spinlock_t              irq_phys_map_lock;
> +     struct rb_root          irq_phys_map;
>  };
>
>  struct vgic_v2_cpu_if {
> @@ -307,6 +319,9 @@ struct vgic_cpu {
>               struct vgic_v2_cpu_if   vgic_v2;
>               struct vgic_v3_cpu_if   vgic_v3;
>       };
> +
> +     /* Protected by the distributor's irq_phys_map_lock */
> +     struct rb_root  irq_phys_map;
>  };
>
>  #define LR_EMPTY     0xff
> @@ -331,6 +346,9 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
>  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 vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, struct irq_phys_map *map);
>
>  #define irqchip_in_kernel(k) (!!((k)->arch.vgic.in_kernel))
>  #define vgic_initialized(k)  (!!((k)->arch.vgic.nr_cpus))
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index 59ed7a3..c6604f2 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -24,6 +24,7 @@
>  #include <linux/of.h>
>  #include <linux/of_address.h>
>  #include <linux/of_irq.h>
> +#include <linux/rbtree.h>
>  #include <linux/uaccess.h>
>
>  #include <linux/irqchip/arm-gic.h>
> @@ -84,6 +85,8 @@ static void vgic_retire_disabled_irqs(struct kvm_vcpu *vcpu);
>  static void vgic_retire_lr(int lr_nr, int irq, struct kvm_vcpu *vcpu);
>  static struct vgic_lr vgic_get_lr(const struct kvm_vcpu *vcpu, int lr);
>  static void vgic_set_lr(struct kvm_vcpu *vcpu, int lr, struct vgic_lr lr_desc);
> +static struct irq_phys_map *vgic_irq_map_search(struct kvm_vcpu *vcpu,
> +                                             int virt_irq);
>
>  static const struct vgic_ops *vgic_ops;
>  static const struct vgic_params *vgic;
> @@ -1585,6 +1588,112 @@ static irqreturn_t vgic_maintenance_handler(int irq, void *data)
>       return IRQ_HANDLED;
>  }
>
> +static struct rb_root *vgic_get_irq_phys_map(struct kvm_vcpu *vcpu,
> +                                          int virt_irq)
> +{
> +     if (virt_irq < VGIC_NR_PRIVATE_IRQS)
> +             return &vcpu->arch.vgic_cpu.irq_phys_map;
> +     else
> +             return &vcpu->kvm->arch.vgic.irq_phys_map;
> +}
> +
> +struct irq_phys_map *vgic_map_phys_irq(struct kvm_vcpu *vcpu,
> +                                    int virt_irq, int irq)
> +{
> +     struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> +     struct rb_root *root = vgic_get_irq_phys_map(vcpu, virt_irq);
> +     struct rb_node **new = &root->rb_node, *parent = NULL;
> +     struct irq_phys_map *new_map;
> +     struct irq_desc *desc;
> +     struct irq_data *data;
> +     int phys_irq;
> +
> +     desc = irq_to_desc(irq);
> +     if (!desc) {
> +             kvm_err("kvm_arch_timer: can't obtain interrupt descriptor\n");

I guess kvm_arch_timer: is a left-over of the original user?

> +             return NULL;
> +     }
> +
> +     data = irq_desc_get_irq_data(desc);
> +     while (data->parent_data)
> +             data = data->parent_data;
> +
> +     phys_irq = data->hwirq;

So if I get this correctly we "cache" hwirq/phys_irq in this map to get
a cheaper access to it, but actually it is redundant since we have
Linux' irq number, isn't it?
Are we sure that the irqdomain mapping of irq and phys_irq never will
change while this map entry is valid? This is probably true for the
timer, but does that still hold in the future with other devices?
(see also the next email for more rationale)

Cheers,
Andre.

> +
> +     spin_lock(&dist->irq_phys_map_lock);
> +
> +     /* Boilerplate rb_tree code */
> +     while (*new) {
> +             struct irq_phys_map *this;
> +
> +             this = container_of(*new, struct irq_phys_map, node);
> +             parent = *new;
> +             if (this->virt_irq < virt_irq)
> +                     new = &(*new)->rb_left;
> +             else if (this->virt_irq > virt_irq)
> +                     new = &(*new)->rb_right;
> +             else {
> +                     new_map = this;
> +                     goto out;
> +             }
> +     }
> +
> +     new_map = kzalloc(sizeof(*new_map), GFP_KERNEL);
> +     if (!new_map)
> +             goto out;
> +
> +     new_map->virt_irq = virt_irq;
> +     new_map->phys_irq = phys_irq;
> +     new_map->irq = irq;
> +
> +     rb_link_node(&new_map->node, parent, new);
> +     rb_insert_color(&new_map->node, root);
> +
> +out:
> +     spin_unlock(&dist->irq_phys_map_lock);
> +     return new_map;
> +}
> +
> +static struct irq_phys_map *vgic_irq_map_search(struct kvm_vcpu *vcpu,
> +                                             int virt_irq)
> +{
> +     struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> +     struct rb_root *root = vgic_get_irq_phys_map(vcpu, virt_irq);
> +     struct rb_node *node = root->rb_node;
> +     struct irq_phys_map *this = NULL;
> +
> +     spin_lock(&dist->irq_phys_map_lock);
> +
> +     while (node) {
> +             this = container_of(node, struct irq_phys_map, node);
> +
> +             if (this->virt_irq < virt_irq)
> +                     node = node->rb_left;
> +             else if (this->virt_irq > virt_irq)
> +                     node = node->rb_right;
> +             else
> +                     break;
> +     }
> +
> +     spin_unlock(&dist->irq_phys_map_lock);
> +     return this;
> +}
> +
> +int vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, struct irq_phys_map *map)
> +{
> +     struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> +
> +     if (!map)
> +             return -EINVAL;
> +
> +     spin_lock(&dist->irq_phys_map_lock);
> +     rb_erase(&map->node, vgic_get_irq_phys_map(vcpu, map->virt_irq));
> +     spin_unlock(&dist->irq_phys_map_lock);
> +
> +     kfree(map);
> +     return 0;
> +}
> +
>  void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
>  {
>       struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
> @@ -1835,6 +1944,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>               goto out_unlock;
>
>       spin_lock_init(&kvm->arch.vgic.lock);
> +     spin_lock_init(&kvm->arch.vgic.irq_phys_map_lock);
>       kvm->arch.vgic.in_kernel = true;
>       kvm->arch.vgic.vgic_model = type;
>       kvm->arch.vgic.vctrl_base = vgic->vctrl_base;
>

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