Subject: Re: [PATCH linux-next v3] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures

From: Eli Cohen <[email-masked]>
Date: Wed, 15 Apr 2015 08:17:26 +0300

Acked-by: Eli Cohen <eli-VPRAkNaXOzVWk0Htik3J/[email-masked]>

On Wed, Apr 15, 2015 at 11:19:17AM +0800, Honggang Li wrote:
> If CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for x86 systems and physical
> memory is more than 4GB, dma_map_page may return a valid memory
> address which greater than 0xffffffff. As a result, the mlx5 device page
> allocator RB tree will be initialized with valid addresses greater than
> 0xfffffff.
> 
> However, (addr & PAGE_MASK) set the high four bytes to zeros. So, it's
> impossible for the function, free_4k, to release the pages whose
> addresses greater than 4GB. Memory leaks. And mlx5_ib module can't
> release the pages when user try to remove the module, as a result,
> system hang.
> 
> [root@rdma05 root]# dmesg  | grep addr | head
> addr             = 3fe384000
> addr & PAGE_MASK =  fe384000
> [root@rdma05 root]# rmmod mlx5_ib   <---- hang on
> 
> ---------------------- cosnole log -----------------
> mlx5_ib 0000:04:00.0: irq 138 for MSI/MSI-X
>   alloc irq_desc for 139 on node -1
>   alloc kstat_irqs on node -1
> mlx5_ib 0000:04:00.0: irq 139 for MSI/MSI-X
> 0000:04:00.0:free_4k:221:(pid 1519): page not found
> 0000:04:00.0:free_4k:221:(pid 1519): page not found
> 0000:04:00.0:free_4k:221:(pid 1519): page not found
> 0000:04:00.0:free_4k:221:(pid 1519): page not found
> ---------------------- cosnole log -----------------
> 
> Fix(bf0bf77 mlx5: Support communicating arbitrary host page size to
> firmware)
> 
> Signed-off-by: Honggang Li <[email-masked]>
> ---
>  .../net/ethernet/mellanox/mlx5/core/pagealloc.c    |   10 ++++++----
>  1 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> index df22383..8a64542 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> @@ -211,26 +211,28 @@ static int alloc_4k(struct mlx5_core_dev *dev, u64 *addr)
>  	return 0;
>  }
>  
> +#define MLX5_U64_4K_PAGE_MASK ((~(u64)0U) << PAGE_SHIFT)
> +
>  static void free_4k(struct mlx5_core_dev *dev, u64 addr)
>  {
>  	struct fw_page *fwp;
>  	int n;
>  
> -	fwp = find_fw_page(dev, addr & PAGE_MASK);
> +	fwp = find_fw_page(dev, addr & MLX5_U64_4K_PAGE_MASK);
>  	if (!fwp) {
>  		mlx5_core_warn(dev, "page not found\n");
>  		return;
>  	}
>  
> -	n = (addr & ~PAGE_MASK) >> MLX5_ADAPTER_PAGE_SHIFT;
> +	n = (addr & ~MLX5_U64_4K_PAGE_MASK) >> MLX5_ADAPTER_PAGE_SHIFT;
>  	fwp->free_count++;
>  	set_bit(n, &fwp->bitmask);
>  	if (fwp->free_count == MLX5_NUM_4K_IN_PAGE) {
>  		rb_erase(&fwp->rb_node, &dev->priv.page_root);
>  		if (fwp->free_count != 1)
>  			list_del(&fwp->list);
> -		dma_unmap_page(&dev->pdev->dev, addr & PAGE_MASK, PAGE_SIZE,
> -			       DMA_BIDIRECTIONAL);
> +		dma_unmap_page(&dev->pdev->dev, addr & MLX5_U64_4K_PAGE_MASK,
> +			       PAGE_SIZE, DMA_BIDIRECTIONAL);
>  		__free_page(fwp->page);
>  		kfree(fwp);
>  	} else if (fwp->free_count == 1) {
> -- 
> 1.7.1
> 
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