linux-kernel - Re: [PATCH linux-next v2] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T

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Message-Id: <20150414.140546.1390992213156919928.davem@davemloft.net>
Date:	Tue, 14 Apr 2015 14:05:46 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	honli@...hat.com
Cc:	eli@...lanox.com, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux-next v2] mlx5: wrong page mask if
 CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures

From: Honggang Li <honli@...hat.com>
Date: Mon, 13 Apr 2015 17:21:58 +0800

> 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@...a05 root]# dmesg  | grep addr | head
> addr             = 3fe384000
> addr & PAGE_MASK =  fe384000
> [root@...a05 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 -----------------
> 
> Signed-off-by: Honggang Li <honli@...hat.com>

Please someone at Mellanox review this.
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