Re: [PATCH v4 6/6] arm: dma-mapping: updates to limit dma_mask and iommu mapping size

[Murali Karicheri <m-karicheri2-l0cyMroinI0@public.gmane.org>]

On 01/27/2015 06:34 AM, Catalin Marinas wrote:
> On Tue, Jan 27, 2015 at 11:12:32AM +0000, Robin Murphy wrote:
>> On 23/01/15 22:32, Murali Karicheri wrote:
>>> Limit the dma_mask to minimum of dma_mask and dma_base + size - 1.
>>>
>>> Also arm_iommu_create_mapping() has size parameter of size_t and
>>> arm_setup_iommu_dma_ops() can take a value higher than that. So
>>> limit the size to SIZE_MAX.
>>>
>>> Signed-off-by: Murali Karicheri<m-karicheri2-l0cyMroinI0@public.gmane.org>
>>> ---
>>>    arch/arm/mm/dma-mapping.c |   10 ++++++++++
>>>    1 file changed, 10 insertions(+)
>>>
>>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>>> index 7864797..a1f9030 100644
>>> --- a/arch/arm/mm/dma-mapping.c
>>> +++ b/arch/arm/mm/dma-mapping.c
>>> @@ -2004,6 +2004,13 @@ static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
>>>    	if (!iommu)
>>>    		return false;
>>>
>>> +	/*
>>> +	 * currently arm_iommu_create_mapping() takes a max of size_t
>>> +	 * for size param. So check this limit for now.
>>> +	 */
>>> +	if (size>  SIZE_MAX)
>>> +		return false;
>>> +
>>>    	mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
>>>    	if (IS_ERR(mapping)) {
>>>    		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
>>> @@ -2053,6 +2060,9 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
>>>    {
>>>    	struct dma_map_ops *dma_ops;
>>>
>>> +	/* limit dma_mask to the lower of the two values */
>>> +	*dev->dma_mask = min((*dev->dma_mask), (dma_base + size - 1));
>>> +
>>
>> Is there any reason not to do this in of_dma_configure? It seems like
>> something everyone could benefit from - I'd cooked up a dodgy workaround
>> for the same issue in my arm64 IOMMU code, but handling it generically
>> in common code would be much nicer.

Ok Will move this to of_dma_configure().

Murali

>
> I agree. I started something here:
>
> http://article.gmane.org/gmane.linux.kernel/1835096
>
> but I don't remember to have got to a clear conclusion.
>


-- 
Murali Karicheri
Linux Kernel, Texas Instruments