> On Fri, Nov 06 2020 at 09:14, Jason Gunthorpe wrote: >> On Fri, Nov 06, 2020 at 09:48:34AM +0000, Tian, Kevin wrote: >> For instance you could put a "disable IMS" flag in the ACPI tables, in >> the config space of the emuulated root port, or any other areas that >> clearly belong to the platform. >> >> The OS logic would be >> - If no IMS information found then use IMS (Bare metal) >> - If the IMS disable flag is found then >> - If (future) hypercall available and the OS knows how to use it >> then use IMS >> - If no hypercall found, or no OS knowledge, fail IMS > > That does not work because an older hypervisor would not have that > disable flag and the guest kernel would assume to be on bare metal (if > no other indicators are there). In the absence of a forward-thinking design from Intel perhaps we could use the existence of an IOMMU with interrupt remapping and not caching mode as the indication that it's bare metal? -- dwmw2
