kvm: Introduce kvm_irqchip_add/remove_irqfd

Add services to associate an eventfd file descriptor as input with an
IRQ line as output. Such a line can be an input pin of an in-kernel
irqchip or a virtual line returned by kvm_irqchip_add_route.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

kvm-all.c

@@ -1108,6 +1108,21 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
     return virq;
 }
 
+static int kvm_irqchip_assign_irqfd(KVMState *s, int fd, int virq, bool assign)
+{
+    struct kvm_irqfd irqfd = {
+        .fd = fd,
+        .gsi = virq,
+        .flags = assign ? 0 : KVM_IRQFD_FLAG_DEASSIGN,
+    };
+
+    if (!kvm_irqchip_in_kernel()) {
+        return -ENOSYS;
+    }
+
+    return kvm_vm_ioctl(s, KVM_IRQFD, &irqfd);
+}
+
 #else /* !KVM_CAP_IRQ_ROUTING */
 
 static void kvm_init_irq_routing(KVMState *s)
@@ -1123,8 +1138,23 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
 {
     abort();
 }
+
+static int kvm_irqchip_assign_irqfd(KVMState *s, int fd, int virq, bool assign)
+{
+    abort();
+}
 #endif /* !KVM_CAP_IRQ_ROUTING */
 
+int kvm_irqchip_add_irqfd(KVMState *s, int fd, int virq)
+{
+    return kvm_irqchip_assign_irqfd(s, fd, virq, true);
+}
+
+int kvm_irqchip_remove_irqfd(KVMState *s, int fd, int virq)
+{
+    return kvm_irqchip_assign_irqfd(s, fd, virq, false);
+}
+
 static int kvm_irqchip_create(KVMState *s)
 {
     QemuOptsList *list = qemu_find_opts("machine");

kvm-stub.c

@@ -140,3 +140,13 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
 void kvm_irqchip_release_virq(KVMState *s, int virq)
 {
 }
+
+int kvm_irqchip_add_irqfd(KVMState *s, int fd, int virq)
+{
+    return -ENOSYS;
+}
+
+int kvm_irqchip_remove_irqfd(KVMState *s, int fd, int virq)
+{
+    return -ENOSYS;
+}

kvm.h

@@ -215,4 +215,7 @@ int kvm_set_ioeventfd_pio_word(int fd, uint16_t adr, uint16_t val, bool assign);
 
 int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg);
 void kvm_irqchip_release_virq(KVMState *s, int virq);
+
+int kvm_irqchip_add_irqfd(KVMState *s, int fd, int virq);
+int kvm_irqchip_remove_irqfd(KVMState *s, int fd, int virq);
 #endif