[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [RFC] Hypercalls from HVM guests
Keir Fraser wrote: > 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 Yep. We should not use PCI device detection to detect such Xen-specific MMU features. And we should use PCI device detection to detect a virtual device because the guest needs to initialize and set up the plumbing (e.g. interrupt lines) as a device. I think such an initial implementation for Xen MMU can use CPUID (with whatever index), and I think we can come back with a specific value for the index when a patch is ready. Jun --- Intel Open Source Technology Center _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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