On Wed, Apr 12, 2023 at 01:43:26PM +0100, Marc Zyngier wrote: > What makes it safe? How does VFIO ensures that the memory type used is > correct in all circumstances? This has to hold for *ANY* device, not > just your favourite toy of the day. Nothing in this patch is horribly > wrong, but the above question must be answered before we can consider > any of this. In VFIO we now have the concept of "variant drivers" which work with specific PCI IDs. The variant drivers can inject device specific knowledge into VFIO. In this series the driver injects the cachable pgprot when it creates some of the VMAs because it knows the PCI IDs it supports, parses the ACPI description, and knows for sure that the memory it puts in the cachable VMA is linked with a cache coherent interconnect. The generic vfio-pci path is not changed, so 'any device' is not relevant here. Jason
