Re: [Xen-devel] [PATCH v3 13/13] xen/iommu: smmu: Advertise when the SMMU support coherent table walk

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-01-30 at 18:49 +0000, Julien Grall wrote:
> @@ -2896,6 +2911,16 @@ static __init int arm_smmu_dt_init(struct 
> dt_device_node *dev,
>       if ( !rc )
>               iommu_set_ops(&arm_smmu_iommu_ops);
>  
> +     /*
> +      * The last added SMMU is the first element of arm_smmu_devices.
> +      * It's not necessary to take the lock because only the boot CPU is
> +      * initialized the SMMU devices.

Why is only the last added SMMU of interest? Do we not need to take the
union and/or intersection of them all?

Perhaps the code which calls iommu_set_feature should gain an else which
calls iommu_clear_feature, and between them they can ensure that
platform_features is correctly updated?

> +      */
> +     smmu = list_entry(arm_smmu_devices.next, typeof(*smmu), list);
> +     ASSERT(smmu != NULL);
> +
> +     platform_features &= smmu->features;
> +
>       return rc;
>  }
>  



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