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+++ This bug was initially created as a clone of Bug #1689216 +++
Description of problem:
Starting a libvirt domain with host-passthrough (equivalent to -cpu host) or
host-model (a CPU model expanded from "host" via query-cpu-model-expansion is
passed to -cpu) on a host with nested VMX enabled cannot be migrated, saved,
or snapshotted. The domain doesn't even need or want to use VMX.
This is a regression introduced in 3.1.0 by
commit d98f26073bebddcd3da0ba1b86c3a34e840c0fb8
Author: Paolo Bonzini <pbonzini>
AuthorDate: Wed Nov 14 10:38:13 2018 +0100
Commit: Paolo Bonzini <pbonzini>
CommitDate: Tue Nov 27 15:06:14 2018 +0100
target/i386: kvm: add VMX migration blocker
Nested VMX does not support live migration yet. Add a blocker
until that is worked out.
Nested SVM only does not support it, but unfortunately it is
enabled by default for -cpu host so we cannot really disable it.
Signed-off-by: Paolo Bonzini <pbonzini>
Unfortunately, VMX is automatically enabled for -cpu host too. The only
difference between SVM and VMX is that kvm_amd automatically enabled nested,
while it has to be enabled manually for kvm_intel.
Version-Release number of selected component (if applicable):
qemu-kvm-3.1.0-18.module+el8+2834+fa8bb6e2.x86_64
How reproducible:
100%
Steps to Reproduce:
1. modprobe -r kvm_intel
2. modprobe kvm_intel nested=1
3. /usr/libexec/qemu-kvm -cpu host -qmp stdin
4. {"execute":"qmp_capabilities"}
5. {"execute":"migrate","arguments":{"uri":"tcp://localhost:1234"}}
Alternatively via libvirt:
1. start a domain with either host-passthrough or host-model CPU
2. virsh managedsave $DOM
Actual results:
{"error": {"class": "GenericError", "desc": "Nested VMX virtualization does not support live migration yet"}}
or a corresponding libvirt error:
internal error: unable to execute QEMU command 'migrate': Nested VMX virtualization does not support live migration yet
----
<jdenemar> bonzini: if we want to keep the check in I think we should make sure vmx is not added to -cpu host unless non-migratable features are requested