Re: [PATCH RFC] net/mlx4: Remove improper usage of dma_alloc_coherent().

[Ido Shamay <idos@dev.mellanox.co.il>]

On 4/13/2015 12:33 AM, Ido Shamay wrote:
> On 4/7/2015 10:43 PM, Ido Shamay wrote:
>> On 4/7/2015 2:00 AM, David Daney wrote:
>>> From: David Daney <david.daney@cavium.com>
>>>
>>> The dma_alloc_coherent() function returns a virtual address which can
>>> be used for coherent access to the underlying memory.  On some
>>> architectures, like arm64, undefined behavior results if this memory is
>>> also accessed via virtual mappings that are not coherent. Because of
>>> their undefined nature, operations like virt_to_page() return garbage
>>> when passed virtual addresses obtained from dma_alloc_coherent().  Any
>>> subsequent mappings via vmap() of the garbage page values are unusable
>>> and result in bad things like bus errors (synchronous aborts in ARM64
>>> speak).
>>>
>>> The MLX4 driver contains code that does the equivalent of:
>>>
>>>    vmap(virt_to_page(dma_alloc_coherent))
>>>
>>> This results in an OOPs when the device is opened.
>>>
>>> To fix this...
>>>
>>> Always use result of dma_alloc_coherent() directly.
> Acked-by: Ido Shamay <idos@mellanox.com>
> Thanks David, this is good for us

Hi David,

Are you resending this patch or you want us to do that?