Re: [PATCH v9 1/4] iommu: Move def_domain type check for untrusted device into core

[Will Deacon]

On Sat, Nov 21, 2020 at 09:56:17PM +0800, Lu Baolu wrote:
> So that the vendor iommu drivers are no more required to provide the
> def_domain_type callback to always isolate the untrusted devices.
> 
> Link: 
> https://lore.kernel.org/linux-iommu/243ce89c33fe4b9da4c56ba35aceb...@huawei.com/
> Cc: Shameerali Kolothum Thodi <shameerali.kolothum.th...@huawei.com>
> Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
> ---
>  drivers/iommu/intel/iommu.c |  7 -------
>  drivers/iommu/iommu.c       | 21 ++++++++++++++-------
>  2 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index af3abd285214..6711f78141a4 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2916,13 +2916,6 @@ static int device_def_domain_type(struct device *dev)
>       if (dev_is_pci(dev)) {
>               struct pci_dev *pdev = to_pci_dev(dev);
>  
> -             /*
> -              * Prevent any device marked as untrusted from getting
> -              * placed into the statically identity mapping domain.
> -              */
> -             if (pdev->untrusted)
> -                     return IOMMU_DOMAIN_DMA;
> -
>               if ((iommu_identity_mapping & IDENTMAP_AZALIA) && 
> IS_AZALIA(pdev))
>                       return IOMMU_DOMAIN_IDENTITY;
>  
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 88b0c9192d8c..3256784c0358 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1457,13 +1457,23 @@ struct iommu_group *fsl_mc_device_group(struct device 
> *dev)
>  }
>  EXPORT_SYMBOL_GPL(fsl_mc_device_group);
>  
> -static int iommu_get_def_domain_type(struct device *dev)
> +/* Get the mandatary def_domain type for device. Otherwise, return 0. */
> +static int iommu_get_mandatory_def_domain_type(struct device *dev)
>  {
>       const struct iommu_ops *ops = dev->bus->iommu_ops;
> -     unsigned int type = 0;
> +
> +     if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted)
> +             return IOMMU_DOMAIN_DMA;
>  
>       if (ops->def_domain_type)
> -             type = ops->def_domain_type(dev);
> +             return ops->def_domain_type(dev);
> +
> +     return 0;
> +}
> +
> +static int iommu_get_def_domain_type(struct device *dev)
> +{
> +     int type = iommu_get_mandatory_def_domain_type(dev);
>  
>       return (type == 0) ? iommu_def_domain_type : type;
>  }
> @@ -1645,13 +1655,10 @@ struct __group_domain_type {
>  
>  static int probe_get_default_domain_type(struct device *dev, void *data)
>  {
> -     const struct iommu_ops *ops = dev->bus->iommu_ops;
>       struct __group_domain_type *gtype = data;
>       unsigned int type = 0;
>  
> -     if (ops->def_domain_type)
> -             type = ops->def_domain_type(dev);
> -
> +     type = iommu_get_mandatory_def_domain_type(dev);

afaict, this code is only called from probe_alloc_default_domain(), which
has:

        /* Ask for default domain requirements of all devices in the group */
        __iommu_group_for_each_dev(group, &gtype,
                                   probe_get_default_domain_type);

        if (!gtype.type)
                gtype.type = iommu_def_domain_type;

so is there actually a need to introduce the new
iommu_get_mandatory_def_domain_type() function, given that a type of 0
always ends up resolving to the default domain type?

Will