kvm: add KVM_IRQFD_FLAG_RESAMPLE support

Added an EventNotifier* parameter to
kvm-all.c:kvm_irqchip_add_irqfd_notifier(), in order to give KVM
another eventfd to be used as "resamplefd". See the documentation
in the linux kernel sources in Documentation/virtual/kvm/api.txt
(section 4.75) for more details.
When the added parameter is passed NULL, the behaviour of the
function is unchanged with respect to the previous versions.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: vmaffione

hw/misc/vfio.c

@@ -646,7 +646,7 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
     vector->virq = msg ? kvm_irqchip_add_msi_route(kvm_state, *msg) : -1;
     if (vector->virq < 0 ||
         kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
-                                       vector->virq) < 0) {
+                                       NULL, vector->virq) < 0) {
         if (vector->virq >= 0) {
             kvm_irqchip_release_virq(kvm_state, vector->virq);
             vector->virq = -1;
@@ -814,7 +814,7 @@ static void vfio_enable_msi(VFIODevice *vdev)
         vector->virq = kvm_irqchip_add_msi_route(kvm_state, msg);
         if (vector->virq < 0 ||
             kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
-                                           vector->virq) < 0) {
+                                           NULL, vector->virq) < 0) {
             qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
                                 vfio_msi_interrupt, NULL, vector);
         }

hw/virtio/virtio-pci.c

@@ -508,7 +508,7 @@ static int kvm_virtio_pci_irqfd_use(VirtIOPCIProxy *proxy,
     VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);
     EventNotifier *n = virtio_queue_get_guest_notifier(vq);
     int ret;
-    ret = kvm_irqchip_add_irqfd_notifier(kvm_state, n, irqfd->virq);
+    ret = kvm_irqchip_add_irqfd_notifier(kvm_state, n, NULL, irqfd->virq);
     return ret;
 }
 

include/sysemu/kvm.h

@@ -309,7 +309,8 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg);
 int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg);
 void kvm_irqchip_release_virq(KVMState *s, int virq);
 
-int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n, int virq);
+int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n,
+                                   EventNotifier *rn, int virq);
 int kvm_irqchip_remove_irqfd_notifier(KVMState *s, EventNotifier *n, int virq);
 void kvm_pc_gsi_handler(void *opaque, int n, int level);
 void kvm_pc_setup_irq_routing(bool pci_enabled);

kvm-all.c

@@ -1230,14 +1230,20 @@ int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg)
     return kvm_update_routing_entry(s, &kroute);
 }
 
-static int kvm_irqchip_assign_irqfd(KVMState *s, int fd, int virq, bool assign)
+static int kvm_irqchip_assign_irqfd(KVMState *s, int fd, int rfd, int virq,
+                                    bool assign)
 {
     struct kvm_irqfd irqfd = {
         .fd = fd,
         .gsi = virq,
         .flags = assign ? 0 : KVM_IRQFD_FLAG_DEASSIGN,
     };
 
+    if (rfd != -1) {
+        irqfd.flags |= KVM_IRQFD_FLAG_RESAMPLE;
+        irqfd.resamplefd = rfd;
+    }
+
     if (!kvm_irqfds_enabled()) {
         return -ENOSYS;
     }
@@ -1276,14 +1282,17 @@ int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg)
 }
 #endif /* !KVM_CAP_IRQ_ROUTING */
 
-int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n, int virq)
+int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n,
+                                   EventNotifier *rn, int virq)
 {
-    return kvm_irqchip_assign_irqfd(s, event_notifier_get_fd(n), virq, true);
+    return kvm_irqchip_assign_irqfd(s, event_notifier_get_fd(n),
+           rn ? event_notifier_get_fd(rn) : -1, virq, true);
 }
 
 int kvm_irqchip_remove_irqfd_notifier(KVMState *s, EventNotifier *n, int virq)
 {
-    return kvm_irqchip_assign_irqfd(s, event_notifier_get_fd(n), virq, false);
+    return kvm_irqchip_assign_irqfd(s, event_notifier_get_fd(n), -1, virq,
+           false);
 }
 
 static int kvm_irqchip_create(KVMState *s)