Backport security patches for XSA-297 to XCP-ng 7.5

[stormi]

We'll try to apply the patches to XCP-ng 7.5, which is still supported until the release of XCP-ng 8.0.

[stormi]

An update candidate is available: https://xcp-ng.org/forum/post/12048

Install it with:

yum update --enablerepo='xcp-ng-updates_testing' microcode_ctl xen-dom0-libs xen-dom0-tools xen-hypervisor xen-libs xen-tools

Or revert to the previous version with:

yum downgrade microcode_ctl xen-dom0-libs xen-dom0-tools xen-hypervisor xen-libs xen-tools

It can have two destinies:

• be accepted as an official update if there's enough feedback from the community (probably the last of the 7.5 release)
• or stay in the xcp-ng-updates_testing repository, available for anyone who need it, but not pushed to everyone. That's what will happen if we don't get any feedback.

See https://xcp-ng.org/blog/2019/05/21/xcp-ng-security-bulletin-mds-hardware-vulnerabilities-in-intel-cpus/ for all the details about this update.

[stormi]

XCP-ng 7.5 reached its end of life. We strongly advise to upgrade. These updates will remain available in the xcp-ng-updates_testing repository for those who need them.