Anthony Liguori wrote:
I've been thinking about this wrt the hypercall page in KVM. The
problem is that in a model like KVM (or presumably VMI), migration
gets really difficult if you have anything but a trivial hypercall
page since the hypercall page will change after migration.
If you cannot guarantee the guest isn't executing code within the
hypercall page (or in your case, doing something with paravirt_ops),
then you cannot safely migrate.
Hm, you need to quiesce the kernel in some way when you do a migrate, so
making sure it isn't in a hypercall would be just part of that. In
general you'd make sure all but one CPU is parked somewhere, and the
remaining CPU is doing the suspend, right?
The tricky part for Xen in all this is how to make sure all mfn
references are visible to the hypervisor/toolstack so they can be
remapped; hypercall page contents are not a concern by comparison.
J
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