Re: [RFC, PATCH 1/24] i386 Vmi documentation

Andi Kleen
2006-03-22T21:46:29Z

On Wednesday 22 March 2006 22:34, Chris Wright wrote:
> * Andi Kleen (ak@suse.de) wrote:
> > On Monday 13 March 2006 18:59, Zachary Amsden wrote:
> >
> > > + The general mechanism for providing customized features and
> > > + capabilities is to provide notification of these feature through
> > > + the CPUID call,
> >
> > How should that work since CPUID cannot be intercepted by
> > a Hypervisor (without VMX/SVM)?
>
> Yeah, it requires guest kernel cooperation/modification.

Even then it's useless for many flags because any user program can (and will)
call CPUID directly.

> > > + The net result of these choices is that most of the calls are very
> > > + easy to make from C-code, and calls that are likely to be required in
> > > + low level trap handling code are easy to call from assembler. Most
> > > + of these calls are also very easily implemented by the hypervisor
> > > + vendor in C code, and only the performance critical calls from
> > > + assembler paths require custom assembly implementations.
> > > +
> > > + CORE INTERFACE CALLS
> >
> > Did I miss it or do you never describe how to find these entry points?
>
> It's the ROM interface. For native they are emitted directly inline.
> For non-native, they are emitted as call stubs, which call to the ROM.
> I don't recall if it's in this doc, but the inline patch has all the
> gory details.

Sure the point was if they write this long fancy document why stop
at documenting the last 5%?

-Andi