KVM: x86: Add lowest-priority support for vt-d posted-interrupts

Use vector-hashing to deliver lowest-priority interrupts for
VT-d posted-interrupts. This patch extends kvm_intr_is_single_vcpu()
to support lowest-priority handling.

Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 1a4ca1d..1520d1a 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -798,6 +798,20 @@ out:
        return ret;
 }
 
+/*
+ * This routine tries to handler interrupts in posted mode, here is how
+ * it deals with different cases:
+ * - For single-destination interrupts, handle it in posted mode
+ * - Else if vector hashing is enabled and it is a lowest-priority
+ *   interrupt, handle it in posted mode and use the following mechanism
+ *   to find the destinaiton vCPU.
+ *     1. For lowest-priority interrupts, store all the possible
+ *        destination vCPUs in an array.
+ *     2. Use "guest vector % max number of destination vCPUs" to find
+ *        the right destination vCPU in the array for the lowest-priority
+ *        interrupt.
+ * - Otherwise, use remapped mode to inject the interrupt.
+ */
 bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
                        struct kvm_vcpu **dest_vcpu)
 {
@@ -839,16 +853,44 @@ bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
                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)
+               if (kvm_vector_hashing_enabled() &&
+                               kvm_lowest_prio_delivery(irq)) {
+                       int idx;
+                       unsigned int dest_vcpus;
+
+                       dest_vcpus = hweight16(bitmap);
+                       if (dest_vcpus == 0)
                                goto out;
-               }
 
-               if (dst && kvm_apic_present(dst->vcpu))
+                       idx = kvm_vector_to_index(irq->vector, dest_vcpus,
+                                                 &bitmap, 16);
+
+                       /*
+                        * We may find a hardware disabled LAPIC here, if that
+                        * is the case, print out a error message once for each
+                        * guest and return
+                        */
+                       dst = map->logical_map[cid][idx];
+                       if (!dst && !kvm->arch.disabled_lapic_found) {
+                               kvm->arch.disabled_lapic_found = true;
+                               printk(KERN_INFO
+                                       "Disabled LAPIC found during irq injection\n");
+                               goto out;
+                       }
+
                        *dest_vcpu = dst->vcpu;
-               else
-                       goto out;
+               } else {
+                       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;