Olaf Hering authored Mar 25, 2021 and Jim Fehlig committed Apr 01, 2021

To support domUs with more than 4TB memory it is required to use
LIBXL_API_VERSION >= 0x040800, which uses uint64_t for certained guest
memory related quantities.

Unfortunately this change is not straight forward. While most of the
code in libxl.h handles the various LIBXL_API_VERSION variants
correctly, the check for valid a LIBXL_API_VERSION at the beginning of
the file was broken between Xen 4.7 and 4.13 - it did not cover for
API changes introduced in Xen 4.7 and 4.8. This was fixed with
xen-project/xen@c3999835

, which for libvirt means in practice either
the libxl API from Xen 4.5 or 4.13+ can be used.

This change uses pkgconfig to decide which API can be safely selected.
Xen provides a pkgconfig file since Xen 4.6, which is also the lowest
version expected by libvirt.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>