Am 27.06.2010 um 10:34 schrieb Avi Kivity <[email protected]>:
On 06/26/2010 02:25 AM, Alexander Graf wrote:
We just introduced a new PV interface that screams for
documentation. So here
it is - a shiny new and awesome text file describing the internal
works of
the PPC KVM paravirtual interface.
+Querying for existence
+======================
+
+To find out if we're running on KVM or not, we overlay the PVR
register. Usually
+the PVR register contains an id that identifies your CPU type. If,
however, you
+pass KVM_PVR_PARA in the register that you want the PVR result in,
the register
+still contains KVM_PVR_PARA after the mfpvr call.
+
+ LOAD_REG_IMM(r5, KVM_PVR_PARA)
+ mfpvr r5
+ [r5 still contains KVM_PVR_PARA]
+
+Once determined to run under a PV capable KVM, you can now use
hypercalls as
+described below.
On x86 we allow host userspace to determine whether the guest sees
the paravirt interface (and what features are exposed). This allows
you to live migrate from a newer host to an older host, by not
exposing the newer features.
A very good idea indeed. Let's postpone that to when we expose enough
state to make live migration possible.
Alex
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