KVM: Userspace controlled irq routing

Currently KVM has a static routing from GSI numbers to interrupts (namely,
0-15 are mapped 1:1 to both PIC and IOAPIC, and 16:23 are mapped 1:1 to
the IOAPIC).  This is insufficient for several reasons:

- HPET requires non 1:1 mapping for the timer interrupt
- MSIs need a new method to assign interrupt numbers and dispatch them
- ACPI APIC mode needs to be able to reassign the PCI LINK interrupts to the
  ioapics

This patch implements an interrupt routing table (as a linked list, but this
can be easily changed) and a userspace interface to replace the table.  The
routing table is initialized according to the current hardwired mapping.

Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 200 insertions, 4 deletions

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 5162a411e4d2..a797fa5e6420 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -24,9 +24,24 @@
 
 #include "ioapic.h"
 
+static void kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
+                            struct kvm *kvm, int level)
+{
+#ifdef CONFIG_X86
+        kvm_pic_set_irq(pic_irqchip(kvm), e->irqchip.pin, level);
+#endif
+}
+
+static void kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
+                               struct kvm *kvm, int level)
+{
+        kvm_ioapic_set_irq(kvm->arch.vioapic, e->irqchip.pin, level);
+}
+
 /* This should be called with the kvm->lock mutex held */
 void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
 {
+        struct kvm_kernel_irq_routing_entry *e;
         unsigned long *irq_state = (unsigned long *)&kvm->arch.irq_states[irq];
 
         /* Logical OR for level trig interrupt */
@@ -39,10 +54,9 @@ void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
          * IOAPIC.  So set the bit in both. The guest will ignore
          * writes to the unused one.
          */
-        kvm_ioapic_set_irq(kvm->arch.vioapic, irq, !!(*irq_state));
-#ifdef CONFIG_X86
-        kvm_pic_set_irq(pic_irqchip(kvm), irq, !!(*irq_state));
-#endif
+        list_for_each_entry(e, &kvm->irq_routing, link)
+                if (e->gsi == irq)
+                        e->set(e, kvm, !!(*irq_state));
 }
 
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned gsi)
@@ -123,3 +137,149 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
                         kimn->func(kimn, mask);
 }
 
+static void __kvm_free_irq_routing(struct list_head *irq_routing)
+{
+        struct kvm_kernel_irq_routing_entry *e, *n;
+
+        list_for_each_entry_safe(e, n, irq_routing, link)
+                kfree(e);
+}
+
+void kvm_free_irq_routing(struct kvm *kvm)
+{
+        __kvm_free_irq_routing(&kvm->irq_routing);
+}
+
+int setup_routing_entry(struct kvm_kernel_irq_routing_entry *e,
+                        const struct kvm_irq_routing_entry *ue)
+{
+        int r = -EINVAL;
+        int delta;
+
+        e->gsi = ue->gsi;
+        switch (ue->type) {
+        case KVM_IRQ_ROUTING_IRQCHIP:
+                delta = 0;
+                switch (ue->u.irqchip.irqchip) {
+                case KVM_IRQCHIP_PIC_MASTER:
+                        e->set = kvm_set_pic_irq;
+                        break;
+                case KVM_IRQCHIP_PIC_SLAVE:
+                                e->set = kvm_set_pic_irq;
+                        delta = 8;
+                        break;
+                case KVM_IRQCHIP_IOAPIC:
+                                e->set = kvm_set_ioapic_irq;
+                        break;
+                default:
+                        goto out;
+                }
+                e->irqchip.irqchip = ue->u.irqchip.irqchip;
+                e->irqchip.pin = ue->u.irqchip.pin + delta;
+                break;
+        default:
+                goto out;
+        }
+        r = 0;
+out:
+        return r;
+}
+
+
+int kvm_set_irq_routing(struct kvm *kvm,
+                        const struct kvm_irq_routing_entry *ue,
+                        unsigned nr,
+                        unsigned flags)
+{
+        struct list_head irq_list = LIST_HEAD_INIT(irq_list);
+        struct list_head tmp = LIST_HEAD_INIT(tmp);
+        struct kvm_kernel_irq_routing_entry *e = NULL;
+        unsigned i;
+        int r;
+
+        for (i = 0; i < nr; ++i) {
+                r = -EINVAL;
+                if (ue->gsi >= KVM_MAX_IRQ_ROUTES)
+                        goto out;
+                if (ue->flags)
+                        goto out;
+                r = -ENOMEM;
+                e = kzalloc(sizeof(*e), GFP_KERNEL);
+                if (!e)
+                        goto out;
+                r = setup_routing_entry(e, ue);
+                if (r)
+                        goto out;
+                ++ue;
+                list_add(&e->link, &irq_list);
+                e = NULL;
+        }
+
+        mutex_lock(&kvm->lock);
+        list_splice(&kvm->irq_routing, &tmp);
+        INIT_LIST_HEAD(&kvm->irq_routing);
+        list_splice(&irq_list, &kvm->irq_routing);
+        INIT_LIST_HEAD(&irq_list);
+        list_splice(&tmp, &irq_list);
+        mutex_unlock(&kvm->lock);
+
+        r = 0;
+
+out:
+        kfree(e);
+        __kvm_free_irq_routing(&irq_list);
+        return r;
+}
+
+#define IOAPIC_ROUTING_ENTRY(irq) \
+        { .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,  \
+          .u.irqchip.irqchip = KVM_IRQCHIP_IOAPIC, .u.irqchip.pin = (irq) }
+#define ROUTING_ENTRY1(irq) IOAPIC_ROUTING_ENTRY(irq)
+
+#ifdef CONFIG_X86
+#define SELECT_PIC(irq) \
+        ((irq) < 8 ? KVM_IRQCHIP_PIC_MASTER : KVM_IRQCHIP_PIC_SLAVE)
+#  define PIC_ROUTING_ENTRY(irq) \
+        { .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,  \
+          .u.irqchip.irqchip = SELECT_PIC(irq), .u.irqchip.pin = (irq) % 8 }
+#  define ROUTING_ENTRY2(irq) \
+        IOAPIC_ROUTING_ENTRY(irq), PIC_ROUTING_ENTRY(irq)
+#else
+#  define ROUTING_ENTRY2(irq) \
+        IOAPIC_ROUTING_ENTRY(irq)
+#endif
+
+static const struct kvm_irq_routing_entry default_routing[] = {
+        ROUTING_ENTRY2(0), ROUTING_ENTRY2(1),
+        ROUTING_ENTRY2(2), ROUTING_ENTRY2(3),
+        ROUTING_ENTRY2(4), ROUTING_ENTRY2(5),
+        ROUTING_ENTRY2(6), ROUTING_ENTRY2(7),
+        ROUTING_ENTRY2(8), ROUTING_ENTRY2(9),
+        ROUTING_ENTRY2(10), ROUTING_ENTRY2(11),
+        ROUTING_ENTRY2(12), ROUTING_ENTRY2(13),
+        ROUTING_ENTRY2(14), ROUTING_ENTRY2(15),
+        ROUTING_ENTRY1(16), ROUTING_ENTRY1(17),
+        ROUTING_ENTRY1(18), ROUTING_ENTRY1(19),
+        ROUTING_ENTRY1(20), ROUTING_ENTRY1(21),
+        ROUTING_ENTRY1(22), ROUTING_ENTRY1(23),
+#ifdef CONFIG_IA64
+        ROUTING_ENTRY1(24), ROUTING_ENTRY1(25),
+        ROUTING_ENTRY1(26), ROUTING_ENTRY1(27),
+        ROUTING_ENTRY1(28), ROUTING_ENTRY1(29),
+        ROUTING_ENTRY1(30), ROUTING_ENTRY1(31),
+        ROUTING_ENTRY1(32), ROUTING_ENTRY1(33),
+        ROUTING_ENTRY1(34), ROUTING_ENTRY1(35),
+        ROUTING_ENTRY1(36), ROUTING_ENTRY1(37),
+        ROUTING_ENTRY1(38), ROUTING_ENTRY1(39),
+        ROUTING_ENTRY1(40), ROUTING_ENTRY1(41),
+        ROUTING_ENTRY1(42), ROUTING_ENTRY1(43),
+        ROUTING_ENTRY1(44), ROUTING_ENTRY1(45),
+        ROUTING_ENTRY1(46), ROUTING_ENTRY1(47),
+#endif
+};
+
+int kvm_setup_default_irq_routing(struct kvm *kvm)
+{
+        return kvm_set_irq_routing(kvm, default_routing,
+                                   ARRAY_SIZE(default_routing), 0);
+}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 786a3ae373b0..c65484b471c6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -843,6 +843,7 @@ static struct kvm *kvm_create_vm(void)
         if (IS_ERR(kvm))
                 goto out;
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
+        INIT_LIST_HEAD(&kvm->irq_routing);
         INIT_HLIST_HEAD(&kvm->mask_notifier_list);
 #endif
 
@@ -926,6 +927,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
         spin_lock(&kvm_lock);
         list_del(&kvm->vm_list);
         spin_unlock(&kvm_lock);
+        kvm_free_irq_routing(kvm);
         kvm_io_bus_destroy(&kvm->pio_bus);
         kvm_io_bus_destroy(&kvm->mmio_bus);
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
@@ -1946,6 +1948,36 @@ static long kvm_vm_ioctl(struct file *filp,
                 break;
         }
 #endif
+#ifdef KVM_CAP_IRQ_ROUTING
+        case KVM_SET_GSI_ROUTING: {
+                struct kvm_irq_routing routing;
+                struct kvm_irq_routing __user *urouting;
+                struct kvm_irq_routing_entry *entries;
+
+                r = -EFAULT;
+                if (copy_from_user(&routing, argp, sizeof(routing)))
+                        goto out;
+                r = -EINVAL;
+                if (routing.nr >= KVM_MAX_IRQ_ROUTES)
+                        goto out;
+                if (routing.flags)
+                        goto out;
+                r = -ENOMEM;
+                entries = vmalloc(routing.nr * sizeof(*entries));
+                if (!entries)
+                        goto out;
+                r = -EFAULT;
+                urouting = argp;
+                if (copy_from_user(entries, urouting->entries,
+                                   routing.nr * sizeof(*entries)))
+                        goto out_free_irq_routing;
+                r = kvm_set_irq_routing(kvm, entries, routing.nr,
+                                        routing.flags);
+        out_free_irq_routing:
+                vfree(entries);
+                break;
+        }
+#endif
         default:
                 r = kvm_arch_vm_ioctl(filp, ioctl, arg);
         }
@@ -2012,6 +2044,10 @@ static long kvm_dev_ioctl_check_extension_generic(long arg)
         case KVM_CAP_USER_MEMORY:
         case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
                 return 1;
+#ifdef CONFIG_HAVE_KVM_IRQCHIP
+        case KVM_CAP_IRQ_ROUTING:
+                return 1;
+#endif
         default:
                 break;
         }