On Sun, Nov 08, 2020 at 07:36:34PM +0000, David Woodhouse wrote: > So it does look like we're going to need a hypercall interface to > compose an MSI message on behalf of the guest, for IMS to use. In fact > PCI devices assigned to a guest could use that too, and then we'd only > need to trap-and-remap any attempt to write a Compatibility Format MSI > to the device's MSI table, while letting Remappable Format messages get > written directly. > > We'd also need a way for an OS running on bare metal to *know* that > it's on bare metal and can just compose MSI messages for itself. Since > we do expect bare metal to have an IOMMU, perhaps that is just a > feature flag on the IOMMU? Have the platform firmware advertise if it needs native or virtualized IMS handling. If it advertises neither don't support IMS?
