libxl supports setting the domain real time clock to local time or
UTC via the localtime field of libxl_domain_build_info. Adjustment
of the clock is also supported via the rtc_timeoffset field. The
libvirt libxl driver has never supported these settings, instead
relying on libxl's default of a UTC real time clock with adjustment
set to 0.

There is at least one user that would like the ability to change
the defaults

https://www.redhat.com/archives/libvirt-users/2018-February/msg00059.html

Add support for specifying a local time clock and for specifying an
adjustment for both local time and UTC clocks. Add a test case to
verify the XML to libxl_domain_config conversion.

Local time clock and clock adjustment is already supported by the
XML <-> xl.cfg converter. What is missing is an explicit test for
the conversion. There are plenty of existing tests that all use UTC
with 0 adjustment. Hijack test-fullvirt-tsc-timer to test a local
time clock with 1 hour adjustment.
Signed-off-by: NJim Fehlig <jfehlig@suse.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

The libxl library allows a libxl_domain_config object to be serialized
from/to a JSON string. Use this to allow testing of the XML to
libxl_domain_config conversion process. Test XML is converted to
libxl_domain_config, which is then serialized to json. A json template
corresponding to the test XML is converted to a libxl_domain_config
object using libxl_domain_config_from_json(), and then serialized
back to json using libxl_domain_config_to_json(). The two json
docs are then compared.

Using libxl to convert the json template to a libxl_domain_config
object and then back to json provides a simple way to account for
any changes or additions to the json representation across Xen
releases.
Signed-off-by: NJim Fehlig <jfehlig@suse.com>
[update to v3.5.0-rc1, improve error reporting, use /bin/true emulator]
Signed-off-by: NMarek Marczykowski-Górecki <marmarek@invisiblethingslab.com>