When starting a domain without a CPU model specified in the domain XML,
QEMU will choose a default one. Which is fine unless the domain gets
migrated to another host because libvirt doesn't perform any CPU ABI
checks and the virtual CPU provided by QEMU on the destination host can
differ from the one on the source host.

With QEMU 4.2.0 we can probe for the default CPU model used by QEMU for
a particular machine type and store it in the domain XML. This way the
chosen CPU model is more visible to users and libvirt will make sure
the guest will see the exact same CPU after migration.

Architecture specific notes
- aarch64: We only set the default CPU for TCG domains as KVM requires
  explicit "-cpu host" to work.

- ppc64: The default CPU for KVM is "host" thanks to some hacks in QEMU,
  we will translate the default model to the model corresponding to the
  host CPU ("POWER8" on a Power8 host, "POWER9" on Power9 host, etc.).
  This is not a problem as the corresponding CPU model is in fact an
  alias for "host". This is probably not ideal, but it's not wrong and
  the default virtual CPU configured by libvirt is the same QEMU would
  use. TCG uses various CPU models depending on machine type and its
  version.

- s390x: The default CPU for KVM is "host" while TCG defaults to "qemu".

- x86_64: The default CPU model (qemu64) is not runnable on any host
  with KVM, but QEMU just disables unavailable features and starts
  happily.

https://bugzilla.redhat.com/show_bug.cgi?id=1598151
https://bugzilla.redhat.com/show_bug.cgi?id=1598162Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

To avoid mismatch between host and QEMU capabilities.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

QEMU 4.2.0 will report default CPU types used by each machine type and
we will want to start using it.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Almost all TCG query-machines replies match KVM. The only exceptions are
4.2.0 replies on s390x which differ in the reported default CPU type.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Some specifics of machine types may depend on the accelerator and thus
the data should be moved to virQEMUCapsAccel. The TCG machine types are
just copied from the ones probed for KVM to simplify the changes to
qemucapabilitiestest data files.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

The function copies machine type data from one QEMU caps structure to
another.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

In preparation for making machine types dependent on the accelerator,
the <machine> elements are formatted between <cpu type='kvm'> and
<cpu type='tcg'>.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

All the code for formatting machine type data was moved to a standalone
virQEMUCapsFormatMachines function.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

All the code for loading machine type data was moved to a standalone
virQEMUCapsLoadMachines function.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

To avoid duplicating code which selects the right virQEMUCapsAccel data
to be filled during probing.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

It is a tiny wrapper around virQEMUCapsProbeQMPCPUDefinitions which will
soon get private parameters and thus it cannot be exposed outside
qemu_capabilities.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

And make it use virQEMUCapsGetAccel once rather than repeating the same
code in all functions called from virQEMUCapsFormatAccel.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

And make it use virQEMUCapsGetAccel once rather than repeating the same
code in all functions called from virQEMUCapsLoadAccel.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

It was very similar to virQEMUCapsGetAccel.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

The function can be used to get the pointer to all data which depend on
the accelerator.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

This is container for capabilities data that depend on the accelerator.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

The new functions are designed to load and format capabilities which
depend on the accelerator (host CPU expansion and CPU models).
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

We need to create a mapping between CPU model names and their
corresponding QOM types.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Both virDomainCapsCPUModelsAdd and virDomainCapsCPUModelsAddSteal are so
simple we can just squash the code in a single function.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

We will need to keep some QEMU-specific data for each CPU model
supported by a QEMU binary. Instead of complicating the generic
virDomainCapsCPUModelsPtr, we can just directly store
qemuMonitorCPUDefsPtr returned by the capabilities probing code.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Most of the code moved to a new virQEMUCapsFetchCPUDefinitions function
and the existing virQEMUCapsFetchCPUModels just becomes a small wrapper
around virQEMUCapsFetchCPUDefinitions and virQEMUCapsCPUDefsToModels.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

The functions return virDomainCapsCPUModelsPtr and thus they should be
called *CPUModels for consistency. Functions called *CPUDefinitions will
work on qemuMonitorCPUDefsPtr.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

The function translates qemuMonitorCPUDefsPtr (used by QEMU caps probing
code) into virDomainCapsCPUModelsPtr used by domain capabilities.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

While virDomainCapsCPUModel structure contains 'usable' field with
virDomainCapsCPUUsable type, the lower level structure specific to QEMU
driver used virTriStateBool for the same thing and we had to translate
between them.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>