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SubjectRe: [PATCH linux-next v2] mlx5: wrong page mask if CONFIG_ARCH_DMA_ADDR_T_64BIT enabled for 32Bit architectures
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From: Honggang Li <honli@redhat.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@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 -----------------
>
> Signed-off-by: Honggang Li <honli@redhat.com>

Please someone at Mellanox review this.


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