[PATCH V2 vfio 03/14] vfio/mlx5: Enforce a single SAVE command at a time

Yishai Hadas
2022-12-01T15:31:04Z

Enforce a single SAVE command at a time.

As the SAVE command is an asynchronous one, we must enforce running only
a single command at a time.

This will preserve ordering between multiple calls and protect from
races on the migration file data structure.

This is a must for the next patches from the series where as part of
PRE_COPY we may have multiple images to be saved and multiple SAVE
commands may be issued from different flows.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
---
drivers/vfio/pci/mlx5/cmd.c | 6 ++++++
drivers/vfio/pci/mlx5/cmd.h | 1 +
drivers/vfio/pci/mlx5/main.c | 2 ++
3 files changed, 9 insertions(+)

diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
index 0848bc905d3e..55ee8036f59c 100644
--- a/drivers/vfio/pci/mlx5/cmd.c
+++ b/drivers/vfio/pci/mlx5/cmd.c
@@ -281,6 +281,7 @@ void mlx5vf_mig_file_cleanup_cb(struct work_struct *_work)
dma_unmap_sgtable(mdev->device, &migf->table.sgt, DMA_FROM_DEVICE, 0);
mlx5_core_dealloc_pd(mdev, async_data->pdn);
kvfree(async_data->out);
+ complete(&migf->save_comp);
fput(migf->filp);
}

@@ -321,6 +322,10 @@ int mlx5vf_cmd_save_vhca_state(struct mlx5vf_pci_core_device *mvdev,
return -ENOTCONN;

mdev = mvdev->mdev;
+ err = wait_for_completion_interruptible(&migf->save_comp);
+ if (err)
+ return err;
+
err = mlx5_core_alloc_pd(mdev, &pdn);
if (err)
return err;
@@ -371,6 +376,7 @@ int mlx5vf_cmd_save_vhca_state(struct mlx5vf_pci_core_device *mvdev,
dma_unmap_sgtable(mdev->device, &migf->table.sgt, DMA_FROM_DEVICE, 0);
err_dma_map:
mlx5_core_dealloc_pd(mdev, pdn);
+ complete(&migf->save_comp);
return err;
}

diff --git a/drivers/vfio/pci/mlx5/cmd.h b/drivers/vfio/pci/mlx5/cmd.h
index 921d5720a1e5..8ffa7699872c 100644
--- a/drivers/vfio/pci/mlx5/cmd.h
+++ b/drivers/vfio/pci/mlx5/cmd.h
@@ -37,6 +37,7 @@ struct mlx5_vf_migration_file {
unsigned long last_offset;
struct mlx5vf_pci_core_device *mvdev;
wait_queue_head_t poll_wait;
+ struct completion save_comp;
struct mlx5_async_ctx async_ctx;
struct mlx5vf_async_data async_data;
};
diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
index 6e9cf2aacc52..4081a0f7e057 100644
--- a/drivers/vfio/pci/mlx5/main.c
+++ b/drivers/vfio/pci/mlx5/main.c
@@ -245,6 +245,8 @@ mlx5vf_pci_save_device_data(struct mlx5vf_pci_core_device *mvdev)
stream_open(migf->filp->f_inode, migf->filp);
mutex_init(&migf->lock);
init_waitqueue_head(&migf->poll_wait);
+ init_completion(&migf->save_comp);
+ complete(&migf->save_comp);
mlx5_cmd_init_async_ctx(mvdev->mdev, &migf->async_ctx);
INIT_WORK(&migf->async_data.work, mlx5vf_mig_file_cleanup_cb);
ret = mlx5vf_cmd_query_vhca_migration_state(mvdev,
--
2.18.1