[PATCH v6 05/15] s390-vfio-ap: Callback to get/set vfio device mig state during guest migration

[Anthony Krowiak]

Implements two callbacks related to the current state of a vfio-ap device:
* The callback that sets a new migration state of a vfio-ap device during
  live migration of guests with pass-through access to AP devices. This
  callback is mandatory for VFIO_DEVICE_FEATURE_MIGRATION support.

  The function pointer for this callback is specified via the
  'migration_set_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

* The callback that returns the current vfio device migration state during
  live migration of guests with pass-through access to AP devices.

  The function pointer for this callback is specified via the
  'migration_get_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

Signed-off-by: Anthony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
 drivers/s390/crypto/vfio_ap_migration.c | 130 +++++++++++++++++++++++-
 1 file changed, 128 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 093219e6bb9f..77d15c5cc9af 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -72,16 +72,141 @@ struct vfio_ap_config {
 	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
 };
 
+static struct file *
+vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
+			    enum vfio_device_mig_state new_state)
+{
+	struct vfio_ap_migration_data *mig_data;
+	enum vfio_device_mig_state cur_state;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+	mig_data = matrix_mdev->mig_data;
+	cur_state = mig_data->mig_state;
+	dev_dbg(matrix_mdev->vdev.dev, "%s: %d -> %d\n", __func__, cur_state,
+		new_state);
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_STOP_COPY) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_RESUMING) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
+	     new_state == VFIO_DEVICE_STATE_STOP) ||
+	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
+	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
+	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	/* vfio_mig_get_next_state() does not use arcs other than the above */
+	WARN_ON(true);
+
+	return ERR_PTR(-EINVAL);
+}
+
 static struct file *vfio_ap_set_state(struct vfio_device *vdev,
 				      enum vfio_device_mig_state  new_state)
 {
-	return NULL;
+	int ret;
+	struct file *filp = NULL;
+	struct ap_matrix_mdev *matrix_mdev;
+	enum vfio_device_mig_state next_state;
+	struct vfio_ap_migration_data *mig_data;
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	if (ap_is_se_guest()) {
+		dev_err_once(matrix_mdev->vdev.dev,
+			     "Migration not allowed from or to a Secure Execution guest\n");
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return ERR_PTR(-EPERM);
+	}
+
+	mig_data = matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * Since the implicit pre-open state is RUNNING, a request to set
+	 * RUNNING is a no-op. Any other state transition is invalid before
+	 * open_device.
+	 */
+	if (!mig_data) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		if (new_state == VFIO_DEVICE_STATE_RUNNING)
+			return NULL;
+		return ERR_PTR(-ENODEV);
+	}
+
+	dev_dbg(vdev->dev, "%s -> %d\n", __func__, new_state);
+
+	while (mig_data->mig_state != VFIO_DEVICE_STATE_ERROR &&
+	       mig_data->mig_state != new_state) {
+		ret = vfio_mig_get_next_state(vdev, mig_data->mig_state,
+					      new_state, &next_state);
+		if (ret) {
+			filp = ERR_PTR(ret);
+			break;
+		}
+
+		filp = vfio_ap_transition_to_state(matrix_mdev, next_state);
+		if (IS_ERR(filp))
+			break;
+
+		mig_data->mig_state = next_state;
+
+		if (WARN_ON(filp && new_state != next_state)) {
+			fput(filp);
+			filp = ERR_PTR(-EINVAL);
+			break;
+		}
+	}
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return filp;
 }
 
 static int vfio_ap_get_state(struct vfio_device *vdev,
 			     enum vfio_device_mig_state  *current_state)
 {
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	struct vfio_ap_migration_data *mig_data;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	mig_data =  matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * If mig_data is NULL, report RUNNING as the implicit pre-open state
+	 * so userspace doesn't need to perform any state transition before the
+	 * device becomes active.
+	 */
+	*current_state = (mig_data) ? mig_data->mig_state :
+				      VFIO_DEVICE_STATE_RUNNING;
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return 0;
 }
 
 static int vfio_ap_get_data_size(struct vfio_device *vdev,
@@ -103,6 +228,7 @@ static const struct vfio_migration_ops vfio_ap_migration_ops = {
  */
 void vfio_ap_init_migration_capabilities(struct ap_matrix_mdev *matrix_mdev)
 {
+	/* Live guest migration is not supported for SE guests */
 	if (ap_is_se_guest())
 		return;
 
-- 
2.53.0