From: Jason Gunthorpe jgg@nvidia.com Sent: Friday, October 13, 2023 10:06 PM
On Fri, Oct 13, 2023 at 07:13:34AM +0000, Tian, Kevin wrote:
From: Jason Gunthorpe jgg@nvidia.com Sent: Friday, October 13, 2023 3:10 AM
Also, we probably should feed enforce_cache_coherency through the alloc_hwpt uapi and not try to autodetect it..
In the past we had a long discussion about this with the conclusion that user opt is the ideal model but it's fine to stay with autodetect and existing vfio/kvm contract for coherency detection until we see a real demand for user opt.
Is there anything new which changes your mind to have user opt now?
I guess, I was just looking at the complexity it brings to keep that working.
vfio_file_enforced_coherent() currently just looks at device_iommu_capable() and can be called before attach, assuming an autodetect model.
moving away from autodetect would need a new contract which I hesitate to bother with at this point.