[PATCH v2 12/19] iommu/arm-smmu-v3: Put writing the context descriptor in the right order

[Nicolin Chen]

On Mon, Nov 13, 2023 at 01:53:19PM -0400, Jason Gunthorpe wrote:
> Get closer to the IOMMU API ideal that changes between domains can be
> hitless. The ordering for the CD table entry is not entirely clean from
> this perspective.
> 
> When switching away from a STE with a CD table programmed in it we should
> write the new STE first, then clear any old data in the CD entry.
> 
> If we are programming a CD table for the first time to a STE then the CD
> entry should be programmed before the STE is loaded.
> 
> If we are replacing a CD table entry when the STE already points at the CD
> entry then we just need to do the make/break sequence.
> 
> Lift this code out of arm_smmu_detach_dev() so it can all be sequenced
> properly. The only other caller is arm_smmu_release_device() and it is
> going to free the cdtable anyhow, so it doesn't matter what is in it.
> 
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>

Reviewed-by: Nicolin Chen <nicolinc at nvidia.com>