RE: Early test for 32- vs 64-bit hvm domain?

["Dan Magenheimer" <dan.magenheimer@oracle.com>]

> Dan Magenheimer, le Tue 29 Jan 2008 17:01:22 -0700, a écrit :
> > What is the proper way to test to see if an hvm domain is destined
> > to be x86 vs x86_64 whilst still early in its initialization in the
> > hypervisor, e.g. in hvm_vcpu_initialise(v) or 
> hvm_domain_initialise(d)?
> > Is this information pased down from hvmloader or does it get
> > discovered somehow?  Or maybe it is not possible to determine
> > until a vcpu actually starts executing?
> 
> As long as e.g. Linux has not started (i.e. during bios and grub for
> instance), you can't know whether that will be a 64bit Linux 
> or a 32bit
> Linux.

That's what I was afraid of...

Then what is the earliest point in the execution of an x86_64
domain/vcpu in *xen* where hvm_long_mode_enabled(v) will work
properly? E.g. in Linux/x86_64 is long mode set early in __start?
And is this done via a hypercall or an emulated instruction?

Thanks,
Dan