[PATCH v2 2/2] vfio: Replace the iommu notifier with a device list

[Tian, Kevin]

> From: Jason Gunthorpe
> Sent: Wednesday, June 8, 2022 7:02 AM
> 
> Instead of bouncing the function call to the driver op through a blocking
> notifier just have the iommu layer call it directly.
> 
> Register each device that is being attached to the iommu with the lower
> driver which then threads them on a linked list and calls the appropriate
> driver op at the right time.
> 
> Currently the only use is if dma_unmap() is defined.
> 
> Also, fully lock all the debugging tests on the pinning path that a
> dma_unmap is registered.
>
... 
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index c13b9290e35759..4ddb1f1abd238b 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -67,7 +67,8 @@ struct vfio_iommu {
>  	struct list_head	iova_list;
>  	struct mutex		lock;
>  	struct rb_root		dma_list;
> -	struct blocking_notifier_head notifier;
> +	struct list_head	device_list;
> +	struct mutex		device_list_lock;

emulated_device_list or unmap_device_list, to be more accurate?

btw a few lines downward there is already a emulated_iommu_groups.
the two sounds a bit overlapping given mdev's iommu group is faked
and singleton. Wonder whether it's cleaner to just reuse the existing field...