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...@intel.com>
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/irq_comm.c         | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f8c0ec3..b8832e5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1180,4 +1180,6 @@ int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, 
u64 *data);
 void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
 void kvm_deliver_pmi(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 72298b3..9e42645 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -299,6 +299,30 @@ 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;
+
+       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;
+
+               r++;
+               *dest_vcpu = vcpu;
+       }
+
+       if (r == 1)
+               return true;
+       else
+               return false;
+}
+
 #define IOAPIC_ROUTING_ENTRY(irq) \
        { .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,  \
          .u.irqchip = { .irqchip = KVM_IRQCHIP_IOAPIC, .pin = (irq) } }
-- 
2.1.0

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