[systemd-devel] [Xen-devel] [PATCH v1] core: mount xenfs, ignore proc-xen.mount (#6442, #6662)

[Jan Beulich]

>>> On 29.11.17 at 16:38, <olaf at aepfle.de> wrote:
> The detection of ConditionVirtualisation= relies on the presence of
> /proc/xen/capabilities. If the file exists and contains the string
> "control_d", the running system is a dom0 and VIRTUALIZATION_NONE should
> be set. In case /proc/xen exists, or some sysfs files indicate "xen",
> VIRTUALIZATION_XEN should be set to indicate the system is a domU.
> 
> With an (old) xenlinux based kernel, /proc/xen/capabilities is always
> available and the detection described above works always. But with a
> pvops based kernel, xenfs must be mounted on /proc/xen to get
> "capabilities". Up to now this was done by a proc-xen.mount unit, which
> is part of xen.git. Since the mounting happens "late", other units may
> be scheduled before "proc-xen.mount". If these other units make use of
> "ConditionVirtualisation=", the virtualization detection returns
> incorect results. detect_vm() will set VIRTUALIZATION_XEN because "xen"
> is found in sysfs. This value will be cached. Once xenfs is mounted,
> the next process that runs detect_vm() will get VIRTUALIZATION_NONE.

With all of the above, was it considered to check /sys/hypervisor
alongside with or perhaps even in preference to /proc/xen?

Jan