KVM: Define a new interface kvm_intr_is_single_vcpu()

This patch defines a new interface kvm_intr_is_single_vcpu(),
which can returns whether the interrupt is for single-CPU or not.

It is used by VT-d PI, since now we only support single-CPU
interrupts, For lowest-priority interrupts, if user configures
it via /proc/irq or uses irqbalance to make it single-CPU, we
can use PI to deliver the interrupts to it. Full functionality
of lowest-priority support will be added later.

Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 91 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d064cb2e19e8..ba4e5673e604 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1241,4 +1241,7 @@ int x86_set_memory_region(struct kvm *kvm,
 bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
 
+bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+                             struct kvm_vcpu **dest_vcpu);
+
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 177460998bb0..39f833f8132e 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -297,6 +297,33 @@ out:
         return r;
 }
 
+bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+                             struct kvm_vcpu **dest_vcpu)
+{
+        int i, r = 0;
+        struct kvm_vcpu *vcpu;
+
+        if (kvm_intr_is_single_vcpu_fast(kvm, irq, dest_vcpu))
+                return true;
+
+        kvm_for_each_vcpu(i, vcpu, kvm) {
+                if (!kvm_apic_present(vcpu))
+                        continue;
+
+                if (!kvm_apic_match_dest(vcpu, NULL, irq->shorthand,
+                                        irq->dest_id, irq->dest_mode))
+                        continue;
+
+                if (++r == 2)
+                        return false;
+
+                *dest_vcpu = vcpu;
+        }
+
+        return r == 1;
+}
+EXPORT_SYMBOL_GPL(kvm_intr_is_single_vcpu);
+
 #define IOAPIC_ROUTING_ENTRY(irq) \
         { .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,  \
           .u.irqchip = { .irqchip = KVM_IRQCHIP_IOAPIC, .pin = (irq) } }
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 2f4c0d0cbe0a..944b38a56929 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -755,6 +755,65 @@ out:
         return ret;
 }
 
+bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+                        struct kvm_vcpu **dest_vcpu)
+{
+        struct kvm_apic_map *map;
+        bool ret = false;
+        struct kvm_lapic *dst = NULL;
+
+        if (irq->shorthand)
+                return false;
+
+        rcu_read_lock();
+        map = rcu_dereference(kvm->arch.apic_map);
+
+        if (!map)
+                goto out;
+
+        if (irq->dest_mode == APIC_DEST_PHYSICAL) {
+                if (irq->dest_id == 0xFF)
+                        goto out;
+
+                if (irq->dest_id >= ARRAY_SIZE(map->phys_map))
+                        goto out;
+
+                dst = map->phys_map[irq->dest_id];
+                if (dst && kvm_apic_present(dst->vcpu))
+                        *dest_vcpu = dst->vcpu;
+                else
+                        goto out;
+        } else {
+                u16 cid;
+                unsigned long bitmap = 1;
+                int i, r = 0;
+
+                if (!kvm_apic_logical_map_valid(map))
+                        goto out;
+
+                apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
+
+                if (cid >= ARRAY_SIZE(map->logical_map))
+                        goto out;
+
+                for_each_set_bit(i, &bitmap, 16) {
+                        dst = map->logical_map[cid][i];
+                        if (++r == 2)
+                                goto out;
+                }
+
+                if (dst && kvm_apic_present(dst->vcpu))
+                        *dest_vcpu = dst->vcpu;
+                else
+                        goto out;
+        }
+
+        ret = true;
+out:
+        rcu_read_unlock();
+        return ret;
+}
+
 /*
  * Add a pending IRQ into lapic.
  * Return 1 if successfully added and 0 if discarded.
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 7259d272416f..fde8e35d5850 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -168,4 +168,6 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
 
 void wait_lapic_expire(struct kvm_vcpu *vcpu);
 
+bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+                        struct kvm_vcpu **dest_vcpu);
 #endif