Jeremy Fitzhardinge wrote:
Anthony Liguori wrote:
The whole point of using the instruction is to allow hypercalls to be
used in many locations. This has the nice side effect of not
requiring a central hypercall initialization routine in the guest to
fetch the hypercall page. A PV driver can be completely independent
of any other code provided that it restricts itself to it's hypercall
namespace.
I see. So you take the fault, disassemble the instruction, see that its
another CPU's vmcall instruction, and then replace it with the current
CPU's vmcall?
Yup.
Xen is currently using 0/1/2. I had thought it was only using 0/1.
The intention was not to squash Xen's current CPUID usage so that it
would still be possible for Xen to make use of the guest code. Can we
agree that Xen won't squash leaves 3/4 or is it not worth trying to be
compatible at this point?
No, the point is that you're supposed to work out which hypervisor it is
from the signature in leaf 0, and then the hypervisor can put anything
it wants in the other leaves.
Yeah, see, the initial goal was to make it possible to use the KVM
paravirtualizations on other hypervisors. However, I don't think this
is really going to be possible in general so maybe it's better to just
use leaf 0. I'll let others chime in before sending a new patch.
Regards,
Anthony Liguori
J
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