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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.02.14 at 18:31, Julien Grall <julien.grall@xxxxxxxxxx> 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.

Jan


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