On Wed, Jul 7, 2021 at 12:42 PM Jim Mattson <jmattson@google.com> wrote:
On Wed, Jul 7, 2021 at 8:09 AM Eduardo Habkost <ehabkost@redhat.com> wrote:
CCing libvir-list, Jiri Denemark, Michal Privoznik, so they are aware that the definition of "supported CPU features" will probably become a bit more complex in the future.
Has there ever been a clear definition? Family, model, and stepping, for instance: are these the only values supported? That would make cross-platform migration impossible. What about the vendor string? Is that the only value supported? That would make cross-vendor migration impossible. For the maximum input value for basic CPUID information (CPUID.0H:EAX), is that the only value supported, or is it the maximum value supported? On the various individual feature bits, does a '1' imply that '0' is also supported, or is '1' the only value supported? What about the feature bits with reversed polarity (e.g. CPUID.(EAX=07H,ECX=0):EBX.FDP_EXCPTN_ONLY[bit 6])?
This API has never made sense to me. I have no idea how to interpret what it is telling me.
Is this about GET_SUPPORTED_CPUID, QEMU's query-cpu-model-expansion & related commands, or the libvirt CPU APIs? -- Eduardo