Re: [Xen-devel] [RFC] Hypercalls from HVM guests

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 7 Apr 2006, at 18:24, Petersson, Mats wrote:

> Good question - the way I'd say is to look at CPUID to see if it's
> "GeunineIntel" or "AuthenticAMD", but I'm not sure if that's the BEST.
> Of course, this assumes the code is already aware that it's in a HVM
> environment, which I'm not sure if you know that or not at the point 
> you
> need to know if it's AMD or Intel... Of course, if CPUID is 
> intercepted,
> it may return other things (but it's against the "rules" to lie about
> the brand of the CPU!)
I like the idea of stealing some MSR space for this, and doing some 
initial interaction with the underlying hypervisor platform via 
RDMSR/WRMSR to known MSRs. We could 'read' an 'MSR' that would tell us 
the correct instruction sequence to do a hypercall (either directly, or 
maybe tell us a 'physical address' to read the hypercall transport 
information from -- then we could have a hypercall transfer page just 
as we already do for paravirtualised guests).
We just need to pick some MSRs that won't get used by Intel or AMD in 
the future. There's quite a lot of addressing space to carve up though. 
:-)
 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel