qemu/target
Christian Borntraeger 0280b3eb7c s390x/kvm: use cpu model for gscb on compat machines
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. 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. We also need to change the migration for guarded
storage.
Additional discussions about host-model are still pending but are out
of scope of this patch.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Cornelia Huck <Cornelia Huck <cohuck@redhat.com>
Acked-by: Halil Pasic <pasic@linux.vnet.ibm.com>
2017-10-30 09:03:45 +01:00
..
alpha Capstone disassembler 2017-10-27 08:04:51 +01:00
arm Capstone disassembler 2017-10-27 08:04:51 +01:00
cris Capstone disassembler 2017-10-27 08:04:51 +01:00
hppa Capstone disassembler 2017-10-27 08:04:51 +01:00
i386 Capstone disassembler 2017-10-27 08:04:51 +01:00
lm32 Capstone disassembler 2017-10-27 08:04:51 +01:00
m68k Capstone disassembler 2017-10-27 08:04:51 +01:00
microblaze Capstone disassembler 2017-10-27 08:04:51 +01:00
mips Capstone disassembler 2017-10-27 08:04:51 +01:00
moxie tcg: Initialize cpu_env generically 2017-10-24 13:53:42 -07:00
nios2 Capstone disassembler 2017-10-27 08:04:51 +01:00
openrisc Capstone disassembler 2017-10-27 08:04:51 +01:00
ppc Capstone disassembler 2017-10-27 08:04:51 +01:00
s390x s390x/kvm: use cpu model for gscb on compat machines 2017-10-30 09:03:45 +01:00
sh4 Capstone disassembler 2017-10-27 08:04:51 +01:00
sparc Capstone disassembler 2017-10-27 08:04:51 +01:00
tilegx tcg: Initialize cpu_env generically 2017-10-24 13:53:42 -07:00
tricore Capstone disassembler 2017-10-27 08:04:51 +01:00
unicore32 Capstone disassembler 2017-10-27 08:04:51 +01:00
xtensa Capstone disassembler 2017-10-27 08:04:51 +01:00