On 03.02.2022 12:06, Roger Pau Monne wrote: > Prevent libxl from creating guests that attempts to use PoD together > with an IOMMU, even if no devices are actually assigned. > > While the hypervisor could support using PoD together with an IOMMU as > long as no devices are assigned, such usage seems doubtful. There's no > guarantee the guest has ballooned down enough memory for PoD to no > longer be active, and thus a later assignment of a PCI device to such > domain could fail.
That's not a precise description of the constraint: The guest ballooning down enough only means entries == cache, but for device assignment we need entries == 0 (and a guarantee that no new entries can appear, but I think this is already the case once a guest was launched). (FWIW the wording in code comment and log message read fine to me.) Jan
