[PATCH v2 08/16] s390/vfio-ap: Transition device migration state from STOP to RESUMING

Anthony Krowiak
2026-04-07T20:51:24Z

Transitioning from VFIO_DEVICE_STATE_STOP to VFIO_DEVICE_STATE_RESUMING
starts a process of restoring the device state of the vfio device on the
target system. To prepare for restoring the device state, open a file
stream to receive the guest's AP configuration saved when the device state
on the source system transitioned from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
drivers/s390/crypto/vfio_ap_migration.c | 55 ++++++++++++++++++++++++-
1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index aadc362edf78..c78e24767d20 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -311,6 +311,46 @@ vfio_ap_save_mdev_state(struct ap_matrix_mdev *matrix_mdev)
return mig_data->saving_migf;
}

+static ssize_t vfio_ap_resume_write(struct file *filp, const char __user *buf,
+ size_t len, loff_t *pos)
+{
+ /* TODO */
+ return -EOPNOTSUPP;
+}
+
+static const struct file_operations vfio_ap_resume_fops = {
+ .owner = THIS_MODULE,
+ .write = vfio_ap_resume_write,
+ .release = vfio_ap_release_migf,
+};
+
+static struct vfio_ap_migration_file *
+vfio_ap_resume_mdev_state(struct ap_matrix_mdev *matrix_mdev)
+{
+ struct vfio_ap_migration_data *mig_data;
+ struct vfio_ap_migration_file *migf;
+ struct file *filp;
+
+ lockdep_assert_held(&matrix_dev->mdevs_lock);
+ mig_data = matrix_mdev->mig_data;
+
+ migf = vfio_ap_allocate_migf(matrix_mdev);
+ if (IS_ERR(migf))
+ return ERR_CAST(migf);
+
+ filp = vfio_ap_open_file_stream(migf, &vfio_ap_resume_fops, O_WRONLY);
+ if (IS_ERR(filp)) {
+ vfio_ap_deallocate_migf(migf);
+ return ERR_CAST(filp);
+ }
+
+ migf->matrix_mdev = matrix_mdev;
+ migf->filp = filp;
+ mig_data->resuming_migf = migf;
+
+ return migf;
+}
+
static struct file *
vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
enum vfio_device_mig_state new_state)
@@ -344,10 +384,21 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
return NULL;
}

+ /*
+ * Starts the process of restoring the state of the vfio-ap device
+ * on the target host by creating a filestream to be used to transfer
+ * the internal state of the vfio-ap device on the source host that
+ * was saved during the STOP_COPY phase of the migration.
+ */
if (cur_state == VFIO_DEVICE_STATE_STOP &&
new_state == VFIO_DEVICE_STATE_RESUMING) {
- /* TODO */
- return ERR_PTR(-EOPNOTSUPP);
+ migf = vfio_ap_resume_mdev_state(matrix_mdev);
+ if (IS_ERR(migf))
+ return ERR_CAST(migf);
+
+ get_file(migf->filp);
+
+ return migf->filp;
}

if (cur_state == VFIO_DEVICE_STATE_RESUMING &&
--
2.52.0