From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v4 18/21] xen/arm: p2m: Clean cache PT when
 the IOMMU doesn't support coherent walk
Date: Fri, 02 May 2014 16:15:56 +0100
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To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel@lists.xenproject.org, stefano.stabellini@citrix.com, ian.campbell@citrix.com, tim@xen.org
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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