Re: [RFC 16/20] vfio/type1: Export symbols for dma [un]map code sharing

[Jason Gunthorpe]

On Sun, Sep 19, 2021 at 02:38:44PM +0800, Liu Yi L wrote:
> [HACK. will fix in v2]
> 
> There are two options to impelement vfio type1v2 mapping semantics in
> /dev/iommu.
> 
> One is to duplicate the related code from vfio as the starting point,
> and then merge with vfio type1 at a later time. However vfio_iommu_type1.c
> has over 3000LOC with ~80% related to dma management logic, including:

I can't really see a way forward like this. I think some scheme to
move the vfio datastructure is going to be necessary.

> - the dma map/unmap metadata management
> - page pinning, and related accounting
> - iova range reporting
> - dirty bitmap retrieving
> - dynamic vaddr update, etc.

All of this needs to be part of the iommufd anyhow..

> The alternative is to consolidate type1v2 logic in /dev/iommu immediately,
> which requires converting vfio_iommu_type1 to be a shim driver. 

Another choice is the the datastructure coulde move and the two
drivers could share its code and continue to exist more independently

Jason