[PATCH] iommu/arm-smmu-v3: Add def_domain_type callback

[Robin Murphy]

On 2020-10-29 15:41, Shameer Kolothum wrote:
> With the introduction of def_domain_type in iommu_ops, vendor
> drivers can now inform the iommu generic layer about any specific
> default domain requirement for a device. Any pci dev marked as
> untrusted is now prevented from having an IDENTITY mapping
> domain.
> 
> The callback is also required when the support for dynamically
> changing the default domain of a group is available.

Yes, we want to allow the group type control to work for all drivers, 
ideally...

> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
> ---
>   -Only devices downstream from externally exposed PCIe hierarchies
>    (such as Thunderbolt outside the platform) are currently marked
>    as "untrusted". Not aware of any ARM64 platforms that may use
>    this type of device.
> 
>    Nevertheless, the main motivation for this patch is to have the
>    flexibility of changing the iommu default domain for a group based
>    on the series[1] "iommu: Add support to change default domain of an
>    iommu group" and that mandates vendor iommu driver to provide this
>    callback.
> 
>   -This is tested along with [1] and was able to change the default
>    domain of an iommu group on an HiSilicon D06 hardware.
>   
> 1. https://lore.kernel.org/linux-iommu/20200925190620.18732-1-ashok.raj@intel.com/
> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 26 +++++++++++++++++++++
>   1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index e634bbe60573..d5dbcee995db 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2567,6 +2567,31 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
>   	}
>   }
>   
> +/*
> + * Return the required default domain type for a specific device.
> + *
> + * @dev: the device in query
> + *
> + * Returns:
> + *  - IOMMU_DOMAIN_DMA: device requires a dynamic mapping domain
> + *  - 0: both identity and dynamic domains work for this device
> + */
> +static int arm_smmu_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 Identity mapping domain.
> +		 */
> +		if (pdev->untrusted)
> +			return IOMMU_DOMAIN_DMA;
> +	}

This should be somewhere in core code - it has nothing to do with SMMUv3.

> +
> +	return 0;

I don't strictly object to adding a stub callback for that bit, but why 
can't iommu_change_dev_def_domain() simply assume it from a NULL 
callback? That works for everyone, for no extra cost ;)

Robin.

> +}
> +
>   static struct iommu_ops arm_smmu_ops = {
>   	.capable		= arm_smmu_capable,
>   	.domain_alloc		= arm_smmu_domain_alloc,
> @@ -2589,6 +2614,7 @@ static struct iommu_ops arm_smmu_ops = {
>   	.dev_feat_enabled	= arm_smmu_dev_feature_enabled,
>   	.dev_enable_feat	= arm_smmu_dev_enable_feature,
>   	.dev_disable_feat	= arm_smmu_dev_disable_feature,
> +	.def_domain_type	= arm_smmu_def_domain_type,
>   	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
>   };
>   
>