Re: [RFC] CPUID usage for interaction between Hypervisors and Linux.

[Jeremy Fitzhardinge <jeremy@goop.org>]

H. Peter Anvin wrote:
> With a sufficiently large block, we could use fixed points, e.g. by 
> having each vendor create interfaces in the 0x40SSSSXX range, where 
> SSSS is the PCI ID they use for PCI devices.

Sure, you could do that, but you'd still want to have a signature in 
0x40SSSS00 to positively identify the chunk.  And what if you wanted 
more than 256 leaves?

> Note that I said "create interfaces".  It's important that all about 
> this is who specified the interface -- for "what hypervisor is this" 
> just use 0x40000000 and disambiguate based on that.

"What hypervisor is this?" isn't a very interesting question; if you're 
even asking it then it suggests that something has gone wrong.  Its much 
more useful to ask "what interfaces does this hypervisor support?", and 
enumerating a smallish range of well-known leaves looking for signatures 
is the simplest way to do that.  (We could use signatures derived from 
the PCI vendor IDs which would help with managing that namespace.)

    J