[PATCH V2 vfio 10/14] vfio/mlx5: Introduce vfio precopy ioctl implementation

Yishai Hadas
2022-12-01T15:31:22Z

vfio precopy ioctl returns an estimation of data available for
transferring from the device.

Whenever a user is using VFIO_MIG_GET_PRECOPY_INFO, track the current
state of the device, and if needed, append the dirty data to the
transfer FD data. This is done by saving a middle state.

As mlx5 runs the SAVE command asynchronously, make sure to query for
incremental data only once there is no active save command.
Running both in parallel, might end-up with a failure in the incremental
query command on un-tracked vhca.

Also, a middle state will be saved only after the previous state has
finished its SAVE command and has been fully transferred, this prevents
endless use resources.

Co-developed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
---
drivers/vfio/pci/mlx5/cmd.c | 16 +++++
drivers/vfio/pci/mlx5/main.c | 111 +++++++++++++++++++++++++++++++++++
2 files changed, 127 insertions(+)

diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
index 160fa38fc78d..12e74ecebe64 100644
--- a/drivers/vfio/pci/mlx5/cmd.c
+++ b/drivers/vfio/pci/mlx5/cmd.c
@@ -67,12 +67,25 @@ int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,
{
u32 out[MLX5_ST_SZ_DW(query_vhca_migration_state_out)] = {};
u32 in[MLX5_ST_SZ_DW(query_vhca_migration_state_in)] = {};
+ bool inc = query_flags & MLX5VF_QUERY_INC;
int ret;

lockdep_assert_held(&mvdev->state_mutex);
if (mvdev->mdev_detach)
return -ENOTCONN;

+ /*
+ * In case PRE_COPY is used, saving_migf is exposed while device is
+ * running. Make sure to run only once there is no active save command.
+ * Running both in parallel, might end-up with a failure in the
+ * incremental query command on un-tracked vhca.
+ */
+ if (inc) {
+ ret = wait_for_completion_interruptible(&mvdev->saving_migf->save_comp);
+ if (ret)
+ return ret;
+ }
+
MLX5_SET(query_vhca_migration_state_in, in, opcode,
MLX5_CMD_OP_QUERY_VHCA_MIGRATION_STATE);
MLX5_SET(query_vhca_migration_state_in, in, vhca_id, mvdev->vhca_id);
@@ -82,6 +95,9 @@ int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,

ret = mlx5_cmd_exec_inout(mvdev->mdev, query_vhca_migration_state, in,
out);
+ if (inc)
+ complete(&mvdev->saving_migf->save_comp);
+
if (ret)
return ret;

diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
index ec52c8c4533a..2f5f83f2b2a4 100644
--- a/drivers/vfio/pci/mlx5/main.c
+++ b/drivers/vfio/pci/mlx5/main.c
@@ -294,10 +294,121 @@ static void mlx5vf_mark_err(struct mlx5_vf_migration_file *migf)
wake_up_interruptible(&migf->poll_wait);
}

+static ssize_t mlx5vf_precopy_ioctl(struct file *filp, unsigned int cmd,
+ unsigned long arg)
+{
+ struct mlx5_vf_migration_file *migf = filp->private_data;
+ struct mlx5vf_pci_core_device *mvdev = migf->mvdev;
+ struct mlx5_vhca_data_buffer *buf;
+ struct vfio_precopy_info info = {};
+ loff_t *pos = &filp->f_pos;
+ unsigned long minsz;
+ size_t inc_length = 0;
+ bool end_of_data;
+ int ret;
+
+ if (cmd != VFIO_MIG_GET_PRECOPY_INFO)
+ return -ENOTTY;
+
+ minsz = offsetofend(struct vfio_precopy_info, dirty_bytes);
+
+ if (copy_from_user(&info, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (info.argsz < minsz)
+ return -EINVAL;
+
+ mutex_lock(&mvdev->state_mutex);
+ if (mvdev->mig_state != VFIO_DEVICE_STATE_PRE_COPY &&
+ mvdev->mig_state != VFIO_DEVICE_STATE_PRE_COPY_P2P) {
+ ret = -EINVAL;
+ goto err_state_unlock;
+ }
+
+ /*
+ * We can't issue a SAVE command when the device is suspended, so as
+ * part of VFIO_DEVICE_STATE_PRE_COPY_P2P no reason to query for extra
+ * bytes that can't be read.
+ */
+ if (mvdev->mig_state == VFIO_DEVICE_STATE_PRE_COPY) {
+ /*
+ * Once the query returns it's guaranteed that there is no
+ * active SAVE command.
+ * As so, the other code below is safe with the proper locks.
+ */
+ ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &inc_length,
+ MLX5VF_QUERY_INC);
+ if (ret)
+ goto err_state_unlock;
+ }
+
+ mutex_lock(&migf->lock);
+ if (migf->state == MLX5_MIGF_STATE_ERROR) {
+ ret = -ENODEV;
+ goto err_migf_unlock;
+ }
+
+ buf = mlx5vf_get_data_buff_from_pos(migf, *pos, &end_of_data);
+ if (buf) {
+ if (buf->start_pos == 0) {
+ info.initial_bytes = buf->header_image_size - *pos;
+ } else if (buf->start_pos ==
+ sizeof(struct mlx5_vf_migration_header)) {
+ /* First data buffer following the header */
+ info.initial_bytes = buf->start_pos +
+ buf->length - *pos;
+ } else {
+ info.dirty_bytes = buf->start_pos + buf->length - *pos;
+ }
+ } else {
+ if (!end_of_data) {
+ ret = -EINVAL;
+ goto err_migf_unlock;
+ }
+
+ info.dirty_bytes = inc_length;
+ }
+
+ if (!end_of_data || !inc_length) {
+ mutex_unlock(&migf->lock);
+ goto done;
+ }
+
+ mutex_unlock(&migf->lock);
+ /*
+ * We finished transferring the current state and the device has a
+ * dirty state, save a new state to be ready for.
+ */
+ buf = mlx5vf_get_data_buffer(migf, inc_length, DMA_FROM_DEVICE);
+ if (IS_ERR(buf)) {
+ ret = PTR_ERR(buf);
+ mlx5vf_mark_err(migf);
+ goto err_state_unlock;
+ }
+
+ ret = mlx5vf_cmd_save_vhca_state(mvdev, migf, buf, true, true);
+ if (ret) {
+ mlx5vf_mark_err(migf);
+ mlx5vf_put_data_buffer(buf);
+ goto err_state_unlock;
+ }
+
+done:
+ mlx5vf_state_mutex_unlock(mvdev);
+ return copy_to_user((void __user *)arg, &info, minsz);
+err_migf_unlock:
+ mutex_unlock(&migf->lock);
+err_state_unlock:
+ mlx5vf_state_mutex_unlock(mvdev);
+ return ret;
+}
+
static const struct file_operations mlx5vf_save_fops = {
.owner = THIS_MODULE,
.read = mlx5vf_save_read,
.poll = mlx5vf_save_poll,
+ .unlocked_ioctl = mlx5vf_precopy_ioctl,
+ .compat_ioctl = compat_ptr_ioctl,
.release = mlx5vf_release_file,
.llseek = no_llseek,
};
--
2.18.1