system/ppc/pseries.rst

148 Switching between the KVM-PR and KVM-HV kernel module
151 Currently, there are two implementations of KVM on Power, ``kvm_hv.ko`` and
155 If a host supports both KVM modes, and both KVM kernel modules are loaded, it is
163 KVM-PR
166 KVM-PR uses the so-called **PR**\ oblem state of the PPC CPUs to run the guests,
168 trap and have to be emulated by the host. That means you can run KVM-PR inside
175 privileged instructions run quite slow with KVM-PR. On the other hand, because
180 As KVM-PR can be run inside a pSeries guest, it can also provide nested
183 It is important to notice that, as KVM-HV provides a much better execution
185 years. Maintenance for KVM-PR has been minimal.
187 In order to run KVM-PR guests with POWER9 processors, someone will need to start
190 KVM-HV
193 KVM-HV uses the hypervisor mode of more recent Power processors, that allow
197 Originally, KVM-HV was only available when running on a PowerNV platform (a.k.a.
200 hypervisor mode of the Power CPU, it wasn't possible to run KVM-HV on a guest.
201 This limitation has been lifted, and now it is possible to run KVM-HV inside
202 pSeries guests as well, making nested virtualization possible with KVM-HV.
204 As KVM-HV has access to privileged instructions, guests that use a lot of these
205 can run much faster than with KVM-PR. On the other hand, the guest CPU has to be
207 embedded PPC CPU for the guest with KVM-HV. However, there is at least the
217 run. As long as you are in a supported environment, you can run KVM-PR or KVM-HV
221 | Platform     | Host type  | Bits | Page table format | KVM-HV   | KVM-PR |
251 .. [2] KVM-HV cannot run nested on POWER8 machines.