vfio/mlx5: Enable querying state size which is > 4GB

Once the device supports 'chunk mode' the driver can support state size
which is larger than 4GB.

In that case the device has the capability to split a single image to
multiple chunks as long as the software provides a buffer in the minimum
size reported by the device.

The driver should query for the minimum buffer size required using
QUERY_VHCA_MIGRATION_STATE command with the 'chunk' bit set in its
input, in that case, the output will include both the minimum buffer
size (i.e.  required_umem_size) and also the remaining total size to be
reported/used where that it will be applicable.

At that point in the series the 'chunk' bit is off, the last patch will
activate the feature once all pieces will be ready.

Note:
Before this change we were limited to 4GB state size as of 4 bytes max
value based on the device specification for the query/save/load
commands.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20230911093856.81910-5-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Author: Yishai Hadas

drivers/vfio/pci/mlx5/cmd.c

@@ -86,7 +86,8 @@ int mlx5vf_cmd_resume_vhca(struct mlx5vf_pci_core_device *mvdev, u16 op_mod)
 }
 
 int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,
-					  size_t *state_size, u8 query_flags)
+					  size_t *state_size, u64 *total_size,
+					  u8 query_flags)
 {
 	u32 out[MLX5_ST_SZ_DW(query_vhca_migration_state_out)] = {};
 	u32 in[MLX5_ST_SZ_DW(query_vhca_migration_state_in)] = {};
@@ -128,6 +129,7 @@ int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,
 	MLX5_SET(query_vhca_migration_state_in, in, op_mod, 0);
 	MLX5_SET(query_vhca_migration_state_in, in, incremental,
 		 query_flags & MLX5VF_QUERY_INC);
+	MLX5_SET(query_vhca_migration_state_in, in, chunk, mvdev->chunk_mode);
 
 	ret = mlx5_cmd_exec_inout(mvdev->mdev, query_vhca_migration_state, in,
 				  out);
@@ -139,6 +141,11 @@ int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,
 
 	*state_size = MLX5_GET(query_vhca_migration_state_out, out,
 			       required_umem_size);
+	if (total_size)
+		*total_size = mvdev->chunk_mode ?
+			MLX5_GET64(query_vhca_migration_state_out, out,
+				   remaining_total_size) : *state_size;
+
 	return 0;
 }
 

drivers/vfio/pci/mlx5/cmd.h

@@ -164,6 +164,7 @@ struct mlx5vf_pci_core_device {
 	u8 deferred_reset:1;
 	u8 mdev_detach:1;
 	u8 log_active:1;
+	u8 chunk_mode:1;
 	struct completion tracker_comp;
 	/* protect migration state */
 	struct mutex state_mutex;
@@ -186,7 +187,8 @@ enum {
 int mlx5vf_cmd_suspend_vhca(struct mlx5vf_pci_core_device *mvdev, u16 op_mod);
 int mlx5vf_cmd_resume_vhca(struct mlx5vf_pci_core_device *mvdev, u16 op_mod);
 int mlx5vf_cmd_query_vhca_migration_state(struct mlx5vf_pci_core_device *mvdev,
-					  size_t *state_size, u8 query_flags);
+					  size_t *state_size, u64 *total_size,
+					  u8 query_flags);
 void mlx5vf_cmd_set_migratable(struct mlx5vf_pci_core_device *mvdev,
 			       const struct vfio_migration_ops *mig_ops,
 			       const struct vfio_log_ops *log_ops);

drivers/vfio/pci/mlx5/main.c

@@ -428,7 +428,7 @@ static long mlx5vf_precopy_ioctl(struct file *filp, unsigned int cmd,
 		 * 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);
+							    NULL, MLX5VF_QUERY_INC);
 		if (ret)
 			goto err_state_unlock;
 	}
@@ -505,7 +505,7 @@ static int mlx5vf_pci_save_device_inc_data(struct mlx5vf_pci_core_device *mvdev)
 	if (migf->state == MLX5_MIGF_STATE_ERROR)
 		return -ENODEV;
 
-	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &length,
+	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &length, NULL,
 				MLX5VF_QUERY_INC | MLX5VF_QUERY_FINAL);
 	if (ret)
 		goto err;
@@ -574,7 +574,7 @@ mlx5vf_pci_save_device_data(struct mlx5vf_pci_core_device *mvdev, bool track)
 	INIT_LIST_HEAD(&migf->buf_list);
 	INIT_LIST_HEAD(&migf->avail_list);
 	spin_lock_init(&migf->list_lock);
-	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &length, 0);
+	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &length, NULL, 0);
 	if (ret)
 		goto out_pd;
 
@@ -1195,13 +1195,14 @@ static int mlx5vf_pci_get_data_size(struct vfio_device *vdev,
 	struct mlx5vf_pci_core_device *mvdev = container_of(
 		vdev, struct mlx5vf_pci_core_device, core_device.vdev);
 	size_t state_size;
+	u64 total_size;
 	int ret;
 
 	mutex_lock(&mvdev->state_mutex);
-	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev,
-						    &state_size, 0);
+	ret = mlx5vf_cmd_query_vhca_migration_state(mvdev, &state_size,
+						    &total_size, 0);
 	if (!ret)
-		*stop_copy_length = state_size;
+		*stop_copy_length = total_size;
 	mlx5vf_state_mutex_unlock(mvdev);
 	return ret;
 }