vfio-pci: Generalize setup of simple eventfds

We want another single vector IRQ index to support signaling of
the device request to userspace.  Generalize the error reporting
IRQ index to avoid code duplication.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci_intrs.c

@@ -763,46 +763,60 @@ static int vfio_pci_set_msi_trigger(struct vfio_pci_device *vdev,
 	return 0;
 }
 
-static int vfio_pci_set_err_trigger(struct vfio_pci_device *vdev,
-				    unsigned index, unsigned start,
-				    unsigned count, uint32_t flags, void *data)
+static int vfio_pci_set_ctx_trigger_single(struct eventfd_ctx **ctx,
+					   uint32_t flags, void *data)
 {
 	int32_t fd = *(int32_t *)data;
 
-	if ((index != VFIO_PCI_ERR_IRQ_INDEX) ||
-	    !(flags & VFIO_IRQ_SET_DATA_TYPE_MASK))
+	if (!(flags & VFIO_IRQ_SET_DATA_TYPE_MASK))
 		return -EINVAL;
 
 	/* DATA_NONE/DATA_BOOL enables loopback testing */
 	if (flags & VFIO_IRQ_SET_DATA_NONE) {
-		if (vdev->err_trigger)
-			eventfd_signal(vdev->err_trigger, 1);
+		if (*ctx)
+			eventfd_signal(*ctx, 1);
 		return 0;
 	} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
 		uint8_t trigger = *(uint8_t *)data;
-		if (trigger && vdev->err_trigger)
-			eventfd_signal(vdev->err_trigger, 1);
+		if (trigger && *ctx)
+			eventfd_signal(*ctx, 1);
 		return 0;
 	}
 
 	/* Handle SET_DATA_EVENTFD */
 	if (fd == -1) {
-		if (vdev->err_trigger)
-			eventfd_ctx_put(vdev->err_trigger);
-		vdev->err_trigger = NULL;
+		if (*ctx)
+			eventfd_ctx_put(*ctx);
+		*ctx = NULL;
 		return 0;
 	} else if (fd >= 0) {
 		struct eventfd_ctx *efdctx;
 		efdctx = eventfd_ctx_fdget(fd);
 		if (IS_ERR(efdctx))
 			return PTR_ERR(efdctx);
-		if (vdev->err_trigger)
-			eventfd_ctx_put(vdev->err_trigger);
-		vdev->err_trigger = efdctx;
+		if (*ctx)
+			eventfd_ctx_put(*ctx);
+		*ctx = efdctx;
 		return 0;
 	} else
 		return -EINVAL;
 }
+
+static int vfio_pci_set_err_trigger(struct vfio_pci_device *vdev,
+				    unsigned index, unsigned start,
+				    unsigned count, uint32_t flags, void *data)
+{
+	if (index != VFIO_PCI_ERR_IRQ_INDEX)
+		return -EINVAL;
+
+	/*
+	 * We should sanitize start & count, but that wasn't caught
+	 * originally, so this IRQ index must forever ignore them :-(
+	 */
+
+	return vfio_pci_set_ctx_trigger_single(&vdev->err_trigger, flags, data);
+}
+
 int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
 			    unsigned index, unsigned start, unsigned count,
 			    void *data)