Re: [libvirt] [PATCH v1 0/4] CPU Model Comparsion via QEMU

[Overview] This patch series implements an interface to "query-cpu-model-comparison" (available QEMU ~2.8.0) via virsh cpu-compare. [Using This Feature] Run virsh cpu-compare (ensure you are running the virsh in your build dir) and pass it an xml file describing a cpu definition. You can copy the cpu xml from virsh capabilities (if you want to compare the host cpu to itself), or a cpu defined in any guest xml. Additionally, you can create a cpu xml as such (e.g. for s390x): <cpu> <arch>s390x</arch> <model fallback='forbid'>model_name</model> <feature policy='require|disable' name='feature_name'/> </cpu> NOTE: the presence of <arch> is optional and it will treat the cpu defined in the xml as a host cpu. This will disregard all feature policies (i.e. all features listed will behave with policy='require', even if disable is specified). NOTE: as s390x only supports feature policies 'require' and 'disable', I am uncertain how to handle the other policies when parsing CPUDef to JSON. [Example Output] On an s390x system running a z13.2, this is the expected output (where each file describes a CPU model corresponding to the name of the file): $ virsh cpu-compare zEC12.xml Host CPU is a superset of CPU described in zEC12.xml $ virsh cpu-compare z13.2.xml CPU described in z13.2.xml is identical to host CPU $ virsh cpu-compare z14.xml CPU described in z14.xml is incompatible with host CPU $ virsh cpu-compare z14.xml --error error: Failed to compare host CPU with z14.xml error: the CPU is incompatible with host CPU $ virsh cpu-compare z12345.xml error: Failed to compare host CPU with z12345cpu.xml error: internal error: unable to execute QEMU command 'query-cpu-model-comparison': The CPU definition 'z12345-base' is unknown. [Patch Rundown] The first patch copies the host CPU definition from qemuCaps to virCaps so we can easily access the host CPU model and features when we handle the CPU comparison in qemu_driver. Note that we take care to not clobber anything already stored in the host CPU definition until we have successfully constructed a new host CPU definition.