kvm/x86/running-nested-guests.rst

7 A nested guest is the ability to run a guest inside another guest (it
9 example is a KVM guest that in turn runs on a KVM guest (the rest of
15               | (Nested Guest) |  | (Nested Guest) |
19               |       L1 (Guest Hypervisor)        |
33 - L1 – level-1 guest; a VM running on L0; also called the "guest
36 - L2 – level-2 guest; a VM running on L1, this is the "nested guest"
46           (guest hypervisor), L3 (nested guest).
61   Provider, using nested KVM lets you rent a large enough "guest
62   hypervisor" (level-1 guest).  This in turn allows you to create
66 - Live migration of "guest hypervisors" and their nested guests, for
139 .. note:: If you suspect your L2 (i.e. nested guest) is running slower,
144 Starting a nested guest (x86)
148 able to start an L1 guest with::
153 guest, or for better live migration compatibility, use a named CPU
158 then the guest hypervisor will subsequently be capable of running a
159 nested guest with accelerated KVM.
175 2. The guest hypervisor (L1) must be provided with the ``sie`` CPU
179 3. Now the KVM module can be loaded in the L1 (guest hypervisor)::
187 Migrating an L1 guest, with a  *live* nested guest in it, to another
191 On AMD systems, once an L1 guest has started an L2 guest, the L1 guest
193 "savevm"/"loadvm") until the L2 guest shuts down.  Attempting to migrate
194 or save-and-load an L1 guest while an L2 guest is running will result in
197 guest can no longer be considered stable or secure, and must be restarted.
198 Migrating an L1 guest merely configured to support nesting, while not
202 Migrating an L2 guest is always expected to succeed, so all the following
205 - Migrating a nested guest (L2) to another L1 guest on the *same* bare
208 - Migrating a nested guest (L2) to another L1 guest on a *different*
211 - Migrating a nested guest (L2) to a bare metal host.
226   have KVM enabled for their guest hypervisor (L1), which results in