On 19.12.2022 19:28, Andrew Cooper wrote: > IOMMUs are more tricky still. They are (for most intents and purposes) > mandatory on systems with >254 CPUs. We could in principle start > supporting asymmetric IRQ routing on large systems, but Xen doesn't > currently and it would be a lot work that's definitely not high on the > priority list. At a minimum, this will need expressing in the Kconfig > help text. > > We need to decide whether it is sensible to allow users to turn off > IOMMU support. It probably is, because you could trivially do this by > selecting CONFIG_INTEL only, and booting the result on an AMD system.
One other thing Andrew and I have been talking about: We probably do not want to tie the IOMMU vendor control to CPU vendor one. IOW we'd like to be able to e.g. build a hypervisor supporting Intel (only) as the CPU vendor, but at the same time having support for an AMD IOMMU. > For the names, I don't think AMD_IOMMU vs INTEL_VTD is a sensible. > Probably wants to be INTEL_IOMMU to match. Or simply VTD, covering the case than some other vendor comes up with a clone. But of course we have that same issue with "AMD" and Hygon ... Jan
