vfio/common: Introduce vfio_set_irq_signaling helper

The code used to assign an interrupt index/subindex to an
eventfd is duplicated many times. Let's introduce an helper that
allows to set/unset the signaling for an ACTION_TRIGGER,
ACTION_MASK or ACTION_UNMASK action.

In the error message, we now use errno in case of any
VFIO_DEVICE_SET_IRQS ioctl failure.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

hw/vfio/common.c

@@ -95,6 +95,84 @@ void vfio_mask_single_irqindex(VFIODevice *vbasedev, int index)
     ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
 }
 
+static inline const char *action_to_str(int action)
+{
+    switch (action) {
+    case VFIO_IRQ_SET_ACTION_MASK:
+        return "MASK";
+    case VFIO_IRQ_SET_ACTION_UNMASK:
+        return "UNMASK";
+    case VFIO_IRQ_SET_ACTION_TRIGGER:
+        return "TRIGGER";
+    default:
+        return "UNKNOWN ACTION";
+    }
+}
+
+static const char *index_to_str(VFIODevice *vbasedev, int index)
+{
+    if (vbasedev->type != VFIO_DEVICE_TYPE_PCI) {
+        return NULL;
+    }
+
+    switch (index) {
+    case VFIO_PCI_INTX_IRQ_INDEX:
+        return "INTX";
+    case VFIO_PCI_MSI_IRQ_INDEX:
+        return "MSI";
+    case VFIO_PCI_MSIX_IRQ_INDEX:
+        return "MSIX";
+    case VFIO_PCI_ERR_IRQ_INDEX:
+        return "ERR";
+    case VFIO_PCI_REQ_IRQ_INDEX:
+        return "REQ";
+    default:
+        return NULL;
+    }
+}
+
+int vfio_set_irq_signaling(VFIODevice *vbasedev, int index, int subindex,
+                           int action, int fd, Error **errp)
+{
+    struct vfio_irq_set *irq_set;
+    int argsz, ret = 0;
+    const char *name;
+    int32_t *pfd;
+
+    argsz = sizeof(*irq_set) + sizeof(*pfd);
+
+    irq_set = g_malloc0(argsz);
+    irq_set->argsz = argsz;
+    irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | action;
+    irq_set->index = index;
+    irq_set->start = subindex;
+    irq_set->count = 1;
+    pfd = (int32_t *)&irq_set->data;
+    *pfd = fd;
+
+    if (ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irq_set)) {
+        ret = -errno;
+    }
+    g_free(irq_set);
+
+    if (!ret) {
+        return 0;
+    }
+
+    error_setg_errno(errp, -ret, "VFIO_DEVICE_SET_IRQS failure");
+
+    name = index_to_str(vbasedev, index);
+    if (name) {
+        error_prepend(errp, "%s-%d: ", name, subindex);
+    } else {
+        error_prepend(errp, "index %d-%d: ", index, subindex);
+    }
+    error_prepend(errp,
+                  "Failed to %s %s eventfd signaling for interrupt ",
+                  fd < 0 ? "tear down" : "set up", action_to_str(action));
+    return ret;
+}
+
 /*
  * IO Port/MMIO - Beware of the endians, VFIO is always little endian
  */