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Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for gua
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines |
Date: |
Thu, 26 Oct 2017 10:17:09 +0200 |
On Fri, 20 Oct 2017 16:54:37 +0200
Christian Borntraeger <address@hidden> wrote:
> Starting a guest with
> <os>
> <type arch='s390x' machine='s390-ccw-virtio-2.9'>hvm</type>
> </os>
> <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 <address@hidden>
> Signed-off-by: Christian Borntraeger <address@hidden>
> ---
> 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 <address@hidden>
Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines, Halil Pasic, 2017/10/25
Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines,
Cornelia Huck <=