[PATCH v7 02/24] iommu: Add IOMMU_DOMAIN_PLATFORM

[Jerry Snitselaar]

On Wed, Aug 23, 2023 at 01:47:16PM -0300, Jason Gunthorpe wrote:
> This is used when the iommu driver is taking control of the dma_ops,
> currently only on S390 and power spapr. It is designed to preserve the
> original ops->detach_dev() semantic that these S390 was built around.
> 
> Provide an opaque domain type and a 'default_domain' ops value that allows
> the driver to trivially force any single domain as the default domain.
> 
> Update iommufd selftest to use this instead of set_platform_dma_ops
> 
> Reviewed-by: Lu Baolu <baolu.lu at linux.intel.com>
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
>  drivers/iommu/iommu.c            | 13 +++++++++++++
>  drivers/iommu/iommufd/selftest.c | 14 +++++---------
>  include/linux/iommu.h            |  6 ++++++
>  3 files changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 33bd1107090720..7cedb0640290c8 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -184,6 +184,8 @@ static const char *iommu_domain_type_str(unsigned int t)
>  	case IOMMU_DOMAIN_DMA:
>  	case IOMMU_DOMAIN_DMA_FQ:
>  		return "Translated";
> +	case IOMMU_DOMAIN_PLATFORM:
> +		return "Platform";
>  	default:
>  		return "Unknown";
>  	}
> @@ -1752,6 +1754,17 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
>  
>  	lockdep_assert_held(&group->mutex);
>  
> +	/*
> +	 * Allow legacy drivers to specify the domain that will be the default
> +	 * domain. This should always be either an IDENTITY or PLATFORM domain.
> +	 * Do not use in new drivers.
> +	 */

Would it be worthwhile to mention this in iommu.h for the iommu_ops default_domain?

> +	if (bus->iommu_ops->default_domain) {
> +		if (req_type)
> +			return ERR_PTR(-EINVAL);
> +		return bus->iommu_ops->default_domain;
> +	}
> +
>  	if (req_type)
>  		return __iommu_group_alloc_default_domain(bus, group, req_type);
>  
> diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
> index d48a202a7c3b81..fb981ba97c4e87 100644
> --- a/drivers/iommu/iommufd/selftest.c
> +++ b/drivers/iommu/iommufd/selftest.c
> @@ -281,14 +281,6 @@ static bool mock_domain_capable(struct device *dev, enum iommu_cap cap)
>  	return cap == IOMMU_CAP_CACHE_COHERENCY;
>  }
>  
> -static void mock_domain_set_plaform_dma_ops(struct device *dev)
> -{
> -	/*
> -	 * mock doesn't setup default domains because we can't hook into the
> -	 * normal probe path
> -	 */
> -}
> -
>  static struct iommu_device mock_iommu_device = {
>  };
>  
> @@ -298,12 +290,16 @@ static struct iommu_device *mock_probe_device(struct device *dev)
>  }
>  
>  static const struct iommu_ops mock_ops = {
> +	/*
> +	 * IOMMU_DOMAIN_BLOCKED cannot be returned from def_domain_type()
> +	 * because it is zero.
> +	 */
> +	.default_domain = &mock_blocking_domain,
>  	.owner = THIS_MODULE,
>  	.pgsize_bitmap = MOCK_IO_PAGE_SIZE,
>  	.hw_info = mock_domain_hw_info,
>  	.domain_alloc = mock_domain_alloc,
>  	.capable = mock_domain_capable,
> -	.set_platform_dma_ops = mock_domain_set_plaform_dma_ops,
>  	.device_group = generic_device_group,
>  	.probe_device = mock_probe_device,
>  	.default_domain_ops =
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index d0920b2a9f1c0e..48a18b6e07abff 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -64,6 +64,7 @@ struct iommu_domain_geometry {
>  #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
>  
>  #define __IOMMU_DOMAIN_SVA	(1U << 4)  /* Shared process address space */
> +#define __IOMMU_DOMAIN_PLATFORM	(1U << 5)
>  
>  #define IOMMU_DOMAIN_ALLOC_FLAGS ~__IOMMU_DOMAIN_DMA_FQ
>  /*
> @@ -81,6 +82,8 @@ struct iommu_domain_geometry {
>   *				  invalidation.
>   *	IOMMU_DOMAIN_SVA	- DMA addresses are shared process addresses
>   *				  represented by mm_struct's.
> + *	IOMMU_DOMAIN_PLATFORM	- Legacy domain for drivers that do their own
> + *				  dma_api stuff. Do not use in new drivers.
>   */
>  #define IOMMU_DOMAIN_BLOCKED	(0U)
>  #define IOMMU_DOMAIN_IDENTITY	(__IOMMU_DOMAIN_PT)
> @@ -91,6 +94,7 @@ struct iommu_domain_geometry {
>  				 __IOMMU_DOMAIN_DMA_API |	\
>  				 __IOMMU_DOMAIN_DMA_FQ)
>  #define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SVA)
> +#define IOMMU_DOMAIN_PLATFORM	(__IOMMU_DOMAIN_PLATFORM)
>  
>  struct iommu_domain {
>  	unsigned type;
> @@ -262,6 +266,7 @@ struct iommu_iotlb_gather {
>   * @owner: Driver module providing these ops
>   * @identity_domain: An always available, always attachable identity
>   *                   translation.
> + * @default_domain: If not NULL this will always be set as the default domain.
>   */
>  struct iommu_ops {
>  	bool (*capable)(struct device *dev, enum iommu_cap);
> @@ -297,6 +302,7 @@ struct iommu_ops {
>  	unsigned long pgsize_bitmap;
>  	struct module *owner;
>  	struct iommu_domain *identity_domain;
> +	struct iommu_domain *default_domain;
>  };
>  
>  /**
> -- 
> 2.41.0
>