[libvirt] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines
cohuck at redhat.com
Thu Oct 26 08:17:09 UTC 2017
On Fri, 20 Oct 2017 16:54:37 +0200
Christian Borntraeger <borntraeger at de.ibm.com> wrote:
> Starting a guest with
> <type arch='s390x' machine='s390-ccw-virtio-2.9'>hvm</type>
> <cpu mode='host-model'/>
> on an IBM z14 results in
> "qemu-system-s390x: Some features requested in the CPU model are not
> available in the configuration: gs"
> This is because guarded storage is fenced for compat machines that did not have
> guarded storage support, but libvirt expands the cpu model according to the
> latest available machine.
> While this prevents future migration abort (by not starting the guest at all),
> not being able to start a "host-model" guest is very much unexpected. As it
> turns out, even if we would modify libvirt to not expand the cpu model to
> contain "gs" for compat machines, it cannot guarantee that a migration will
> succeed. For example if the kernel changes its features (or the user has
> nested=1 on one host but not on the other) the migration will fail
> nevertheless. So instead of fencing "gs" for machines <= 2.9 lets allow it for
> all machine types that support the CPU model. This will make "host-model"
> runnable all the time, while relying on the CPU model to reject invalid
> migration attempts.
> Suggested-by: David Hildenbrand <david at redhat.com>
> Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
> hw/s390x/s390-virtio-ccw.c | 8 --------
> include/hw/s390x/s390-virtio-ccw.h | 3 ---
> target/s390x/kvm.c | 2 +-
> 3 files changed, 1 insertion(+), 12 deletions(-)
Acked-by: Cornelia Huck <cohuck at redhat.com>
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