Re: [PATCH v4 18/21] xen/arm: p2m: Clean cache PT when the IOMMU doesn't support coherent walk

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

Hi Jan,

On 04/29/2014 08:40 AM, Jan Beulich wrote:
>>>> On 22.04.14 at 15:14, <julien.grall@linaro.org> wrote:
>> +bool_t iommu_has_feature(struct domain *d, uint32_t feature)
>> +{
>> +    const struct iommu_ops *ops = domain_hvm_iommu(d)->platform_ops;
>> +    uint32_t features = 0;
>> +
>> +    if ( iommu_enabled && ops && ops->features )
>> +        features = ops->features(d);
>> +
>> +    return !!(features & feature);
>> +}
> 
> That's slightly strange a feature check: Passing in a bit mask allows
> the caller to set more than one bit, with obvious ambiguity in what
> this would mean. I'd suggest making this a bit position (with individual
> bits defined via enumeration), at once hiding from the generic caller
> whether eventually there might be more than 32 features defined.

I will create a separate patch to add iommu_has_feature. It will be more
clearer.

Regards,

-- 
Julien Grall