Re: [PATCH v5 01/14] iommu: Add dma ownership management interfaces

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

On 1/5/22 3:23 AM, Jason Gunthorpe wrote:
>>>> The vfio oriented interfaces are,
>>>>
>>>> 	int iommu_group_set_dma_owner(struct iommu_group *group,
>>>> 				      void *owner);
>>>> 	void iommu_group_release_dma_owner(struct iommu_group *group);
>>>> 	bool iommu_group_dma_owner_claimed(struct iommu_group *group);
>>>>
>>>> The device userspace assignment must be disallowed if the set dma owner
>>>> interface returns failure.
>> Can you connect this back to the "never a mixture" from the beginning?
>> If all you cared about was prevent an IOMMU group from containing
>> devices with a mixture of kernel drivers and userspace drivers, I
>> assume you could do that without iommu_device_use_dma_api().  So is
>> this a way to*allow*  a mixture under certain restricted conditions?
> It is not about user/kernel, it is about arbitrating the shared
> group->domain against multiple different requests to set it to
> something else.
> 
> Lu, Given that the word 'user' was deleted from the API entirely it
> makes sense to reword these commit messages to focus less on user vs
> kernel and more on ownership of the domain pointer.

Sure. Will do it.

Best regards,
baolu