Difference between revisions of "Virtualization"

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===Running 64KiB guests on 4KiB hosts===
 
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When trying to start a VM on a host running with [[Page size|4KiB pages]], you might see the following error message:
===Running 64k guests on 4k hosts===
 
When trying to start a VM on a host running with 4k pages, you might see the following error message:
 
  
 
<nowiki>qemu-system-ppc64: Can't support 64 kiB guest pages with 4 kiB host pages with this KVM implementation</nowiki>
 
<nowiki>qemu-system-ppc64: Can't support 64 kiB guest pages with 4 kiB host pages with this KVM implementation</nowiki>

Latest revision as of 22:07, 17 May 2023

Running 64KiB guests on 4KiB hosts

When trying to start a VM on a host running with 4KiB pages, you might see the following error message:

qemu-system-ppc64: Can't support 64 kiB guest pages with 4 kiB host pages with this KVM implementation

There is an easy workaround for this. If running QEMU directly, add the argument -machine pseries,cap-hpt-max-page-size=4096. If running QEMU via libvirt, add the following section[1] to the guest's libvirt XML (via virsh edit [guest name] or the XML tab in virt-manager):

  <features>
    <hpt>
      <maxpagesize unit='KiB'>4</maxpagesize>
    </hpt>
  </features>

Nested KVM

In order to be able to run nested KVM, two things must be satisfied:

  1. The kvm_hv kernel module must be loaded with the nested=1 module argument
  2. The L1 guest must be started with -machine pseries,cap-nested-hv=on as argument to qemu. If running qemu via libvirt, add the following XML fragment to the XML:
  <features>
    <nested-hv state="on"/>
  </features>

Further Information

  • https://gitlab.com/libvirt/libvirt/-/issues/227#note_705948269