s390/vfio-ap: realize the VFIO_DEVICE_GET_IRQ_INFO ioctl

Realize the VFIO_DEVICE_GET_IRQ_INFO ioctl to retrieve the information for
the VFIO device request IRQ.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20230530223538.279198-2-akrowiak@linux.ibm.comSigned-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

drivers/s390/crypto/vfio_ap_ops.c

@@ -1750,7 +1750,32 @@ static int vfio_ap_mdev_get_device_info(unsigned long arg)
 
 	info.flags = VFIO_DEVICE_FLAGS_AP | VFIO_DEVICE_FLAGS_RESET;
 	info.num_regions = 0;
-	info.num_irqs = 0;
+	info.num_irqs = VFIO_AP_NUM_IRQS;
+
+	return copy_to_user((void __user *)arg, &info, minsz) ? -EFAULT : 0;
+}
+
+static ssize_t vfio_ap_get_irq_info(unsigned long arg)
+{
+	unsigned long minsz;
+	struct vfio_irq_info info;
+
+	minsz = offsetofend(struct vfio_irq_info, count);
+
+	if (copy_from_user(&info, (void __user *)arg, minsz))
+		return -EFAULT;
+
+	if (info.argsz < minsz || info.index >= VFIO_AP_NUM_IRQS)
+		return -EINVAL;
+
+	switch (info.index) {
+	case VFIO_AP_REQ_IRQ_INDEX:
+		info.count = 1;
+		info.flags = VFIO_IRQ_INFO_EVENTFD;
+		break;
+	default:
+		return -EINVAL;
+	}
 
 	return copy_to_user((void __user *)arg, &info, minsz) ? -EFAULT : 0;
 }
@@ -1770,6 +1795,9 @@ static ssize_t vfio_ap_mdev_ioctl(struct vfio_device *vdev,
 	case VFIO_DEVICE_RESET:
 		ret = vfio_ap_mdev_reset_queues(&matrix_mdev->qtable);
 		break;
+	case VFIO_DEVICE_GET_IRQ_INFO:
+			ret = vfio_ap_get_irq_info(arg);
+			break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;

include/uapi/linux/vfio.h

@@ -646,6 +646,15 @@ enum {
 	VFIO_CCW_NUM_IRQS
 };
 
+/*
+ * The vfio-ap bus driver makes use of the following IRQ index mapping.
+ * Unimplemented IRQ types return a count of zero.
+ */
+enum {
+	VFIO_AP_REQ_IRQ_INDEX,
+	VFIO_AP_NUM_IRQS
+};
+
 /**
  * VFIO_DEVICE_GET_PCI_HOT_RESET_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 12,
  *					      struct vfio_pci_hot_reset_info)