[PATCH v3 4/9] s390: ap: tools to find a queue with a specific APQN

[Pierre Morel <pmorel@linux.ibm.com>]

We need to find the queue with a specific APQN during the
handling of the interception of the PQAP/AQIC instruction.

To handle the AP associated device reference count we keep
track of it in the vfio_ap_queue until we put the device.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 54 +++++++++++++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_private.h |  1 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 900b9cf..2a52c9b 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -24,6 +24,60 @@
 #define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough"
 #define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device"
 
+/**
+ * vfio_ap_check_apqn: check if a ap_queue is of a given APQN
+ *
+ * Returns 1 if we have a match.
+ * Otherwise returns 0.
+ */
+static int vfio_ap_check_apqn(struct device *dev, void *data)
+{
+	struct vfio_ap_queue *q = dev_get_drvdata(dev);
+
+	return (q->apqn == *(int *)data);
+}
+
+/**
+ * vfio_ap_get_queue: Retrieve a queue with a specific APQN
+ * @apqn: The queue APQN
+ *
+ * Retrieve a queue with a specific APQN from the list of the
+ * devices associated to the vfio_ap_driver.
+ *
+ * The vfio_ap_queue has been already associated with the device
+ * during the probe.
+ * Store the associated device for reference counting
+ *
+ * Returns the pointer to the associated vfio_ap_queue
+ */
+static  __attribute__((unused))
+	struct vfio_ap_queue *vfio_ap_get_queue(int apqn)
+{
+	struct device *dev;
+	struct vfio_ap_queue *q;
+
+	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL, &apqn,
+				 vfio_ap_check_apqn);
+	if (!dev)
+		return NULL;
+	q = dev_get_drvdata(dev);
+	q->dev = dev;
+	return q;
+}
+
+/**
+ * vfio_ap_put_queue: lower device reference count for a queue
+ * @q: The queue
+ *
+ * put the associated device
+ *
+ */
+static  __attribute__((unused)) void vfio_ap_put_queue(struct vfio_ap_queue *q)
+{
+	put_device(q->dev);
+	q->dev = NULL;
+}
+
 static void vfio_ap_matrix_init(struct ap_config_info *info,
 				struct ap_matrix *matrix)
 {
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 8836f01..081f0d7 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -87,6 +87,7 @@ extern int vfio_ap_mdev_register(void);
 extern void vfio_ap_mdev_unregister(void);
 
 struct vfio_ap_queue {
+	struct device *dev;
 	int	apqn;
 };
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.7.4