RE: [PATCH 1/1] iommu/vt-d: Enable ATS before cache tag assignment

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, June 20, 2025 2:08 PM
> 
> Commit <4f1492efb495> ("iommu/vt-d: Revert ATS timing change to fix boot
> failure") placed the enabling of ATS in the probe_finalize callback. This
> occurs after the default domain attachment, which is when the ATS cache
> tag is assigned. Consequently, the device TLB cache tag is missed when the
> domain is attached, leading to the device TLB not being invalidated in the
> iommu_unmap paths.
> 
> Fix it by moving the ATS enabling to the default domain attachment path,
> ensuring ATS is enabled before the cache tag assignment.

this means ATS will never be enabled for drivers with driver_managed_dma
set to '1', as they don't expect their devices attached to the default domain
automatically.

does it make more sense sticking to current way (enabling ATS in
probe_finalize) and assigning cache tag for device tlb at that point?