On Fri, Apr 08, 2022 at 02:28:02PM +0100, Robin Murphy wrote: > > > One nit. Is it logistically more reasonable to put this patch before > > > changing VFIO to always set IOMMU_CACHE? > > > > For bisectability it has to be after > > > > iommu: Redefine IOMMU_CAP_CACHE_COHERENCY as the cap flag for IOMMU_CACHE > > > > Otherwise Intel iommu will stop working with VFIO > > > > The ordering is OK as is because no IOMMU that works with VFIO cares > > about IOMMU_CACHE. > > The Arm SMMU drivers do (without it even coherent traffic would be > downgraded to non-cacheable), but then they also handle > IOMMU_CAP_CACHE_COHERENCY nonsensically, and it happens to work out since > AFAIK there aren't (yet) any Arm-based systems where you can reasonably try > to use VFIO that don't also have hardware-coherent PCI. Thus I don't think > there's any risk of regression for us here. Right, I was unclear, I meant 'requires IOMMU_CACHE to be unset to work with VFIO' Jason
