Re: [RFC for-4.5 12/12] drivers/passthrough: arm: Add support for SMMU drivers

[Julien Grall <julien.grall@linaro.org>]

Hello Jan,

On 20/02/14 08:11, Jan Beulich wrote:
>>>> On 19.02.14 at 18:31, Julien Grall <julien.grall@linaro.org> wrote:
>> On 02/19/2014 05:27 PM, Ian Campbell wrote:
>>> On Wed, 2014-02-19 at 17:21 +0000, Julien Grall wrote:
>>>>>> +#define SZ_4K                               (1 << 12)
>>>>>> +#define SZ_64K                              (1 << 16)
>>>>>> +
>>>>>> +/* Driver options */
>>>>>> +#define SMMU_OPT_SECURE_CONFIG_ACCESS   (1 << 0)
>>>>>
>>>>> Is this just retained to reduce the deviation from the Linux driver?
>>>>> It's no use to us I think. (I suppose that goes for a bunch of other
>>>>> stuff, eg.. the PGSZ_4K stuff, which I will avoid commenting on
>>>>> further).
>>>>
>>>> SZ_4K and SZ_64K is used later in the code.
>>>
>>> But they are actually useless to us aren't they?
>>
>> As we use only 4K page in Xen yes. I kept it because there is few place
>> where the SMMU configuration is not the same.
>>
>> If we want to support 64K page in the future it will harder to had
>> support if this stuff is removed.
>>
>> The constant was added by himself as it doesn't exists on Xen. I can
>> move it into the generic code.
>
> But if possible I'd like to encourage you using PAGE_SIZE_4K to
> match up with what we already got in the IOMMU code. Unless
> deviation from the sources you're cloning is deemed worse than
> consistency within our code.

I think this change is fine. It doesn't fundamentally change the code.

I will update the patch for the next version.

Regards,

-- 
Julien Grall