s390/vfio-ap: add status attribute to AP queue device's sysfs dir

This patch adds a sysfs 'status' attribute to a queue device when it is
bound to the vfio_ap device driver. The field displays a string indicating
the status of the queue device:

Status String:  Indicates:
-------------   ---------
"assigned"      the queue is assigned to an mdev, but is not in use by a
                KVM guest.
"in use"        the queue is assigned to an mdev and is in use by a KVM
                guest.
"unassigned"    the queue is not assigned to an mdev.

The status string will be displayed by the 'lszcrypt' command if the queue
device is bound to the vfio_ap device driver.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
[akrowiak@linux.ibm.com: added check for queue in use by guest]
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 03311a4..e043ae2 100644 (file)
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -17,6 +17,9 @@
 
 #define VFIO_AP_ROOT_NAME "vfio_ap"
 #define VFIO_AP_DEV_NAME "matrix"
+#define AP_QUEUE_ASSIGNED "assigned"
+#define AP_QUEUE_UNASSIGNED "unassigned"
+#define AP_QUEUE_IN_USE "in use"
 
 MODULE_AUTHOR("IBM Corporation");
 MODULE_DESCRIPTION("VFIO AP device driver, Copyright IBM Corp. 2018");
@@ -41,26 +44,95 @@ static struct ap_device_id ap_queue_ids[] = {
 
 MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
 
+static struct ap_matrix_mdev *vfio_ap_mdev_for_queue(struct vfio_ap_queue *q)
+{
+       struct ap_matrix_mdev *matrix_mdev;
+       unsigned long apid = AP_QID_CARD(q->apqn);
+       unsigned long apqi = AP_QID_QUEUE(q->apqn);
+
+       list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) {
+               if (test_bit_inv(apid, matrix_mdev->matrix.apm) &&
+                   test_bit_inv(apqi, matrix_mdev->matrix.aqm))
+                       return matrix_mdev;
+       }
+
+       return NULL;
+}
+
+static ssize_t status_show(struct device *dev,
+                          struct device_attribute *attr,
+                          char *buf)
+{
+       ssize_t nchars = 0;
+       struct vfio_ap_queue *q;
+       struct ap_matrix_mdev *matrix_mdev;
+       struct ap_device *apdev = to_ap_dev(dev);
+
+       mutex_lock(&matrix_dev->lock);
+       q = dev_get_drvdata(&apdev->device);
+       matrix_mdev = vfio_ap_mdev_for_queue(q);
+
+       if (matrix_mdev) {
+               if (matrix_mdev->kvm)
+                       nchars = scnprintf(buf, PAGE_SIZE, "%s\n",
+                                          AP_QUEUE_IN_USE);
+               else
+                       nchars = scnprintf(buf, PAGE_SIZE, "%s\n",
+                                          AP_QUEUE_ASSIGNED);
+       } else {
+               nchars = scnprintf(buf, PAGE_SIZE, "%s\n",
+                                  AP_QUEUE_UNASSIGNED);
+       }
+
+       mutex_unlock(&matrix_dev->lock);
+
+       return nchars;
+}
+
+static DEVICE_ATTR_RO(status);
+
+static struct attribute *vfio_queue_attrs[] = {
+       &dev_attr_status.attr,
+       NULL,
+};
+
+static const struct attribute_group vfio_queue_attr_group = {
+       .attrs = vfio_queue_attrs,
+};
+
 /**
  * vfio_ap_queue_dev_probe: Allocate a vfio_ap_queue structure and associate it
  *                         with the device as driver_data.
  *
  * @apdev: the AP device being probed
  *
- * Return: returns 0 if the probe succeeded; otherwise, returns -ENOMEM if
- *        storage could not be allocated for a vfio_ap_queue object.
+ * Return: returns 0 if the probe succeeded; otherwise, returns an error if
+ *        storage could not be allocated for a vfio_ap_queue object or the
+ *        sysfs 'status' attribute could not be created for the queue device.
  */
 static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
 {
+       int ret;
        struct vfio_ap_queue *q;
 
        q = kzalloc(sizeof(*q), GFP_KERNEL);
        if (!q)
                return -ENOMEM;
+
+       mutex_lock(&matrix_dev->lock);
        dev_set_drvdata(&apdev->device, q);
        q->apqn = to_ap_queue(&apdev->device)->qid;
        q->saved_isc = VFIO_AP_ISC_INVALID;
-       return 0;
+
+       ret = sysfs_create_group(&apdev->device.kobj, &vfio_queue_attr_group);
+       if (ret) {
+               dev_set_drvdata(&apdev->device, NULL);
+               kfree(q);
+       }
+
+       mutex_unlock(&matrix_dev->lock);
+
+       return ret;
 }
 
 /**
@@ -75,6 +147,7 @@ static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
        struct vfio_ap_queue *q;
 
        mutex_lock(&matrix_dev->lock);
+       sysfs_remove_group(&apdev->device.kobj, &vfio_queue_attr_group);
        q = dev_get_drvdata(&apdev->device);
        vfio_ap_mdev_reset_queue(q, 1);
        dev_set_drvdata(&apdev->device, NULL);