This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


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

On 9 Apr 2006, at 14:56, Nakajima, Jun wrote:

This is a different question, and I think detecting a virtual device
(i.e. virtual block device, NIC) or chipset would be a cleaner way at
this point. And that would be proper for the patch that Steve mentioned
(we wrote it). The fact that it's running on a hypervisor does not
necessarily guarantee presence of such virtual devices (in fact they
don't exist today ;-).

If we really need to tell if we are running on a hypervisor at a very
early point or even in user-mode, I think CPUID with "an unused index"
would be the simplest, but so far I haven't seen any usage models that
really require that. If we want to add virtualization hints for
processor architectures (e.g. MMU) in guests, it would be needed.

Executing hypercalls via an indirection page as we do for paravirtualised guests is an attractive idea. That would require more than just 'are we AMD or Intel' and it would be nice to have that future-proofing level of indirection in the initial implementation. We could do that via the PCI device too (e.g., use a BAR) though that doesn't seem so clean to me.

 -- Keir

Xen-devel mailing list