Re: [PATCH v3 02/12] iommu: Introduce iommu_paging_domain_alloc_flags()

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2024/10/17 22:01, Vasant Hegde wrote:
> From: Jason Gunthorpe<jgg@ziepe.ca>
> 
> Currently drivers calls iommu_paging_domain_alloc(dev) to get an
> UNMANAGED domain. This is not sufficient to support PASID with
> UNMANAGED domain as some HW like AMD requires certain page table type
> to support PASIDs.
> 
> Also domain_alloc_paging() passes device as param for domain
> allocation. This is not sufficient for AMD driver to decide the right
> page table.
> 
> Hence add iommu_paging_domain_alloc_flags() API which takes flags as
> parameter. Driver can pass additional parameter to indicate type of
> domain required, etc. iommu_paging_domain_alloc_flags() internally calls
> appropriate callback function to allocate a domain.
> 
> Signed-off-by: Jason Gunthorpe<jgg@ziepe.ca>
> [Added description - Vasant]
> Signed-off-by: Vasant Hegde<vasant.hegde@amd.com>
> Reviewed-by: Jason Gunthorpe<jgg@nvidia.com>
> ---
>   drivers/iommu/iommu.c | 30 ++++++++++++++++++++++++++----
>   include/linux/iommu.h | 14 +++++++++++---
>   2 files changed, 37 insertions(+), 7 deletions(-)

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 811748bec4b0..e13d64ffd14f 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2027,20 +2027,42 @@ struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
>   EXPORT_SYMBOL_GPL(iommu_domain_alloc);
>   
>   /**
> - * iommu_paging_domain_alloc() - Allocate a paging domain
> + * iommu_paging_domain_alloc_flags() - Allocate a paging domain
>    * @dev: device for which the domain is allocated
> + * @flags: Bitmap of iommufd_hwpt_alloc_flags
>    *
>    * Allocate a paging domain which will be managed by a kernel driver. Return
>    * allocated domain if successful, or a ERR pointer for failure.
>    */
> -struct iommu_domain *iommu_paging_domain_alloc(struct device *dev)
> +struct iommu_domain *iommu_paging_domain_alloc_flags(struct device *dev,
> +						     unsigned int flags)
>   {
> +	const struct iommu_ops *ops;
> +	struct iommu_domain *domain;
> +
>   	if (!dev_has_iommu(dev))
>   		return ERR_PTR(-ENODEV);
>   
> -	return __iommu_domain_alloc(dev_iommu_ops(dev), dev, IOMMU_DOMAIN_UNMANAGED);
> +	ops = dev_iommu_ops(dev);
> +
> +	if (ops->domain_alloc_paging && !flags)
> +		domain = ops->domain_alloc_paging(dev);
> +	else if (ops->domain_alloc_user)
> +		domain = ops->domain_alloc_user(dev, flags, NULL, NULL);
> +	else if (ops->domain_alloc && !flags)
> +		domain = ops->domain_alloc(IOMMU_DOMAIN_UNMANAGED);
> +	else
> +		return ERR_PTR(-EOPNOTSUPP);

Above works.

If we want to deprecate domain_alloc and make domain_alloc_user a
generic callback for paging domain allocation, perhaps we can make it
like below:

	if (flags && !ops->domain_alloc_user)
		return ERR_PTR(-EOPNOTSUPP);

	if (ops->domain_alloc_user)
		domain = ops->domain_alloc_user(dev, flags, NULL, NULL);
	else if (ops->domain_alloc_paging)
		domain = ops->domain_alloc_paging(dev);
	else if (ops->domain_alloc)
		domain = ops->domain_alloc(IOMMU_DOMAIN_UNMANAGED);
	else
		return ERR_PTR(-EOPNOTSUPP);

Thanks,
baolu