Bug 61491 - systemd-detect-virt and hostnamectl fail to detect Xen PV
Summary: systemd-detect-virt and hostnamectl fail to detect Xen PV
Alias: None
Product: systemd
Classification: Unclassified
Component: general (show other bugs)
Version: unspecified
Hardware: Other Linux (All)
: medium minor
Assignee: systemd-bugs
QA Contact: systemd-bugs
: 61490 (view as bug list)
Depends on:
Reported: 2013-02-26 08:29 UTC by Andy Melnikov
Modified: 2013-03-07 15:04 UTC (History)
0 users

See Also:
i915 platform:
i915 features:


Description Andy Melnikov 2013-02-26 08:29:52 UTC
When running inside a Xen PV virtual machine, systemd-detect-virt displays "none" and hostnamectl doesn't display "Virtualization" line:

[root@foo ~]# systemd-detect-virt

[root@foo ~]# hostnamectl
   Static hostname: foo
   Pretty hostname: foo
         Icon name: computer
           Chassis: n/a
        Machine ID: baad787b99df4cc7a8ff801dfd96c735
           Boot ID: baad822deca749a496ee91406681ebd6
  Operating System: Foo Linux
            Kernel: Linux 3.x.x-foo
      Architecture: i686

Compare with running in vmware:

[root@bar ~]# systemd-detect-virt
[root@bar ~]# hostnamectl
   Static hostname: bar
Transient hostname: localhost
   Pretty hostname: n/a
         Icon name: computer-vm
           Chassis: vm
        Machine ID: d2016ade07564ecfb465fa009630602e
           Boot ID: 09105e4eea624316a8eda284739dcc45
    Virtualization: vmware
  Operating System: Foo Linux
            Kernel: Linux 3.x.x-foo
      Architecture: i686

One way to detect is to look for presense of /sys/hypervisor/type:

[root@zorro ~]# cat /sys/hypervisor/type

Or /proc/xen/ folder.
Comment 1 Lennart Poettering 2013-03-06 16:13:18 UTC
Hmm, the current code looks for the CPUID virtualization leaf and for the DMI vendor information. Are you suggesting that detecting Xen with that is not possible anymore?


Supporting /sys/hypervisor/type sounds like a good thing, but if the CPUID stuff/DMI stuff could be made work then I'd prefer that.

Could you paste "grep . /sys/class/dmi/id/*" on your xen guest?
Comment 2 Lennart Poettering 2013-03-06 16:17:08 UTC
*** Bug 61490 has been marked as a duplicate of this bug. ***
Comment 3 Andy Melnikov 2013-03-06 16:43:13 UTC
I'm only suggesting that Xen is not detected on my 3 servers from different providers. There are many kinds of Xen: HVM, PV and PVHVM. I have PV, so the existing detection may still work with HVM and PVHVM flavours.

/sys/class/dmi folder doesn't exist. /sys/class contains the following folders, most of them empty:

backlight/    firmware/     leds/         power_supply/ vtconsole/
bdi/          gpio/         mem/          rtc/          watchdog/
block/        graphics/     misc/         thermal/
bsg/          hwmon/        net/          tty/
dma/          input/        pci_bus/      vc/

dmidecode says the following:

# No SMBIOS nor DMI entry point found, sorry.

/proc/cpuinfo contains the following flags:

flags           : fpu de tsc msr pae cx8 sep cmov pat clflush mmx fxsr sse sse2 ss ht nx constant_tsc nonstop_tsc pni pclmulqdq ssse3 sse4_1 sse4_2 popcnt aes hypervisor

Not sure how these translate to CPUID flags but note the hypervisor flag.
Comment 4 Kay Sievers 2013-03-06 17:59:09 UTC
CONFIG_DMIID=y in the kernel probably makes the stuff work for you,
without additional systemd changes.

DMI data is used by other parts of the system too, and we kind of rely on
that being available.
Comment 5 Andy Melnikov 2013-03-06 20:00:14 UTC
CONFIG_DMIID=y is set in kernel config.

It seems Xen lacks DMI support in PV flavour: 


In addition if Xen is every fixed to emulate DMI blocks in
paravirt as it does in full virt then such a check would be wrong.

I infer that Xen PV (paravirtualized), unlike Xen HVM (hardware virtual machine), doesn't emulate DMI blocks yet.
Comment 6 Lennart Poettering 2013-03-07 15:04:11 UTC
git will now check /sys/hypervisor/type.

I didn't actually test this against a real Xen, but I am quite sure this works now.

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