Messages in this thread | | | Date | Mon, 29 Sep 2008 14:49:34 -0700 | From | "H. Peter Anvin" <> | Subject | Re: Use CPUID to communicate with the hypervisor. |
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Jeremy Fitzhardinge wrote: >>> >> Unless there is a central authority assigning these, "we" can do all >> we want, enough people will not pay attention. >> >> Basically, there needs to be a standards document that describes the >> architecture, *and* needs to either have universal buy-in with all the >> vendors or imposed by an authority with enough clout to do so (Intel >> might.) > > I think using fixed offsets is unwise, since there's already contention > for the same leaves. Making sure that each block of leaves (where a > block is 16, 256 or some other number of leaves) is self-describing via > ABI signatures is the only sane way to go. There's still the issue of > assigning ABI signatures to vendors, but that's 1) less of an issue, and > 2) can be self-assigned with very low likelihood of collision. That way > a guest can scan that region of leaf space for ABI signatures it > understand, and can pick and choose among what it finds (but not mix and > match - that sounds like a course for disaster).
If you can't mix and match, there is no point, since very likely all hypervisors will have at least some unique information.
> If we use such a scheme, we can 1) avoid any existing users of that > space, 2) cleanly delimit a hypervisor-agnostic ABI portion of the leaf > space, and 3) allow hypervisors to implement multiple ABIs at once.
Yes, see my previous "half-baked" sketch.
-hpa
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