[PATCH rdma-rc] RDMA/mlx5: Use different doorbell memory for different processes

[PATCH rdma-rc] RDMA/mlx5: Use different doorbell memory for different processes

[Leon Romanovsky]

From: Mark Zhang <markzhang@nvidia.com>

In fork scenario, the parent and child can have same virtual address.
That causes to the list_for_each_entry search return same doorbell location
for all processes.

This patch takes the mm_struct into consideration during search, to make
sure that different doorbell memory is used for the different processes.

Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters")
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/infiniband/hw/mlx5/doorbell.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx5/doorbell.c b/drivers/infiniband/hw/mlx5/doorbell.c
index 40226c75406a..0333b0fe5d8a 100644
--- a/drivers/infiniband/hw/mlx5/doorbell.c
+++ b/drivers/infiniband/hw/mlx5/doorbell.c
@@ -41,6 +41,7 @@ struct mlx5_ib_user_db_page {
 	struct ib_umem	       *umem;
 	unsigned long		user_virt;
 	int			refcnt;
+	struct mm_struct	*mm;
 };
 
 int mlx5_ib_db_map_user(struct mlx5_ib_ucontext *context, unsigned long virt,
@@ -52,7 +53,8 @@ int mlx5_ib_db_map_user(struct mlx5_ib_ucontext *context, unsigned long virt,
 	mutex_lock(&context->db_page_mutex);
 
 	list_for_each_entry(page, &context->db_page_list, list)
-		if (page->user_virt == (virt & PAGE_MASK))
+		if ((current->mm == page->mm) &&
+		    (page->user_virt == (virt & PAGE_MASK)))
 			goto found;
 
 	page = kmalloc(sizeof(*page), GFP_KERNEL);
@@ -71,6 +73,8 @@ int mlx5_ib_db_map_user(struct mlx5_ib_ucontext *context, unsigned long virt,
 		kfree(page);
 		goto out;
 	}
+	mmgrab(current->mm);
+	page->mm = current->mm;
 
 	list_add(&page->list, &context->db_page_list);
 
@@ -91,6 +95,7 @@ void mlx5_ib_db_unmap_user(struct mlx5_ib_ucontext *context, struct mlx5_db *db)
 
 	if (!--db->u.user_page->refcnt) {
 		list_del(&db->u.user_page->list);
+		mmdrop(db->u.user_page->mm);
 		ib_umem_release(db->u.user_page->umem);
 		kfree(db->u.user_page);
 	}
-- 
2.31.1

Re: [PATCH rdma-rc] RDMA/mlx5: Use different doorbell memory for different processes

[Jason Gunthorpe]

On Thu, Jun 03, 2021 at 04:18:03PM +0300, Leon Romanovsky wrote:
> From: Mark Zhang <markzhang@nvidia.com>
> 
> In fork scenario, the parent and child can have same virtual address.
> That causes to the list_for_each_entry search return same doorbell location
> for all processes.
> 
> This patch takes the mm_struct into consideration during search, to make
> sure that different doorbell memory is used for the different processes.
> 
> Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters")
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Mark Zhang <markzhang@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/hw/mlx5/doorbell.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

Applied to for-rc, thanks

Jason