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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.04.14 at 15:14, <julien.grall@xxxxxxxxxx> 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.

Jan


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