Guest CPU definitions with mode='custom' and missing <vendor> are
expected to run on a host CPU from any vendor as long as the required
CPU model can be used as a guest CPU on the host. But even though no CPU
vendor was explicitly requested we would sometimes force it due to a bug
in virCPUUpdate and virCPUTranslate.
The bug would effectively forbid cross vendor migrations even if they
were previously working just fine.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
The API is no longer used anywhere else since it was replaced by a much
saner work flow utilizing new APIs that work on virCPUDefPtr directly:
virCPUCompare, virCPUUpdate, and virCPUTranslate.
Not testing the new work flow caused some bugs to be hidden. This patch
reveals them, but doesn't attempt to fix them. To make sure all test
still pass after this patch, all affected test results are modified to
pretend the tests succeeded. All of the bugs will be fixed in the
following commits and the artificial modifications will be reverted.
The following is the list of bugs in the new CPU model work flow:
- a guest CPU with mode='custom' and missing <vendor/> gets the vendor
copied from host's CPU (the vendor should only be copied to host-model
CPUs):
DO_TEST_UPDATE("x86", "host", "min", VIR_CPU_COMPARE_IDENTICAL)
DO_TEST_UPDATE("x86", "host", "pentium3", VIR_CPU_COMPARE_IDENTICAL)
DO_TEST_GUESTCPU("x86", "host-better", "pentium3", NULL, 0)
- when a guest CPU with mode='custom' needs to be translated into
another model because the original model is not supported by a
hypervisor, the result will have its vendor set to the vendor of the
original CPU model as specified in cpu_map.xml even if the original
guest CPU XML didn't contain <vendor/>:
DO_TEST_GUESTCPU("x86", "host", "guest", model486, 0)
DO_TEST_GUESTCPU("x86", "host", "guest", models, 0)
DO_TEST_GUESTCPU("x86", "host-Haswell-noTSX", "Haswell-noTSX",
haswell, 0)
- legacy POWERx_v* model names are not recognized:
DO_TEST_GUESTCPU("ppc64", "host", "guest-legacy", ppc_models, 0)
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
There's no reason for keeping the features in a linked list. Especially
when we know upfront the total number of features we are loading.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
The mode can be either of "custom" (default), "host-model",
"host-passthrough". The semantics of each mode is described in the
following examples:
- guest CPU is a default model with specified topology:
<cpu>
<topology sockets='1' cores='2' threads='1'/>
</cpu>
- guest CPU matches selected model:
<cpu mode='custom' match='exact'>
<model>core2duo</model>
</cpu>
- guest CPU should be a copy of host CPU as advertised by capabilities
XML (this is a short cut for manually copying host CPU specification
from capabilities to domain XML):
<cpu mode='host-model'/>
In case a hypervisor does not support the exact host model, libvirt
automatically falls back to a closest supported CPU model and
removes/adds features to match host. This behavior can be disabled by
<cpu mode='host-model'>
<model fallback='forbid'/>
</cpu>
- the same as previous returned by virDomainGetXMLDesc with
VIR_DOMAIN_XML_UPDATE_CPU flag:
<cpu mode='host-model' match='exact'>
<model fallback='allow'>Penryn</model> --+
<vendor>Intel</vendor> |
<topology sockets='2' cores='4' threads='1'/> + copied from
<feature policy='require' name='dca'/> | capabilities XML
<feature policy='require' name='xtpr'/> |
... --+
</cpu>
- guest CPU should be exactly the same as host CPU even in the aspects
libvirt doesn't model (such domain cannot be migrated unless both
hosts contain exactly the same CPUs):
<cpu mode='host-passthrough'/>
- the same as previous returned by virDomainGetXMLDesc with
VIR_DOMAIN_XML_UPDATE_CPU flag:
<cpu mode='host-passthrough' match='minimal'>
<model>Penryn</model> --+ copied from caps
<vendor>Intel</vendor> | XML but doesn't
<topology sockets='2' cores='4' threads='1'/> | describe all
<feature policy='require' name='dca'/> | aspects of the
<feature policy='require' name='xtpr'/> | actual guest CPU
... --+
</cpu>
In case a hypervisor doesn't support the exact CPU model requested by a
domain XML, we automatically fallback to a closest CPU model the
hypervisor supports (and make sure we add/remove any additional features
if needed). This patch adds 'fallback' attribute to model element, which
can be used to disable this automatic fallback.
