Currently runtime parameters of the hypervisor cannot be inspected through an
xl command, however they can be changed with the "xl set-parameter" command.
Being able to check these parameters at runtime would be a useful diagnostic
tool.

This patch series implements a new xl command "xl get-parameters"
which takes a string of input parameters and returns their current
values in the hypervisor settings.

Changes v2->v3:

- Several style / formatting fixes
- Limitations for signed integer parameters added in code and commit log.

Changes v1->v2:

- fixed snprintf issues, fixed memory leaks and error handling
- removed unnecessary wrapper function
- OPT_SIZE is handled

Limitations:

- Custom runtime parameters (OPT_CUSTOM) are not supported yet. I'd like
  to do this in a follow-up series. See also discussion at
  https://lists.xenproject.org/archives/html/xen-devel/2019-03/msg01383.html
- For integer parameters (OPT_UINT), only unsigned parameters are printed
  correctly at the moment.

Examples:

xl get-parameters "gnttab_max_frames gnttab_max_maptrack_frames"
gnttab_max_frames gnttab_max_maptrack_frames : 64 1024

xl set-parameters gnttab_max_frames=128

xl get-parameters gnttab_max_frames
gnttab_max_frames : 128

xl get-parameters "gnttab_max_frames gnttab_max_maptrack_frames"
gnttab_max_frames gnttab_max_maptrack_frames : 128 1024

Vasilis Liaskovitis (4):
  xen: add hypercall for getting parameters at runtime
  libxc: add function to get hypervisor parameters
  libxl: add libxl_get_parameters() function
  xl: add new xl command get-parameters

 docs/man/xl.1.pod.in                |   5 ++
 tools/flask/policy/modules/dom0.te  |   2 +-
 tools/libxc/include/xenctrl.h       |   1 +
 tools/libxc/xc_misc.c               |  26 +++++++
 tools/libxl/libxl.c                 |  15 ++++
 tools/libxl/libxl.h                 |   1 +
 tools/xl/xl.h                       |   1 +
 tools/xl/xl_cmdtable.c              |   5 ++
 tools/xl/xl_misc.c                  |  25 ++++++
 xen/common/kernel.c                 | 113 ++++++++++++++++++++++++++++
 xen/common/sysctl.c                 |  52 ++++++++++++-
 xen/include/public/sysctl.h         |  18 +++++
 xen/include/xen/lib.h               |   1 +
 xen/xsm/flask/hooks.c               |   3 +
 xen/xsm/flask/policy/access_vectors |   2 +
 15 files changed, 267 insertions(+), 3 deletions(-)

-- 
2.20.1


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