[RFC] Make xl vcpu-set work in overcommit and with PV guests. (v2).

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Hey,

In Xen 4.3 the 'xl vcpu-set' would not work for CPU overcommit - meaning
where you request more vCPUs than the host has. We added the --ignore-host
parameter to allow the system admin to still do this operation as a stop-gate
solution.

For Xen 4.4 I had posted two (three?) set of patches that try different
things for this. The discussion narrowed down to (and please correct me if
I am incorrect) to: lets still print the warning but let the operation
go ahead without required the --ignore-host parameter. Since the parameter
is baked in it still has to work but we can just ignore it.

The first patch does that. The second patch is a bug I found where the
'xl vcpuset' would not work on PV guests. I think the same issue is with
Xen 4.3 but I am not sure. The patch #2 fixes that.

The patches are also at:

 git://xenbits.xen.org/people/konradwilk/xen.git vcpu.v1.1

The diffstat and log is:

 docs/man/xl.pod.1         | 15 ++++++++++++++-
 tools/libxl/libxl.c       | 28 ++++++++++++++++++++--------
 tools/libxl/xl_cmdimpl.c  | 28 ++++++++++++----------------
 tools/libxl/xl_cmdtable.c |  2 +-
 4 files changed, 47 insertions(+), 26 deletions(-)

Konrad Rzeszutek Wilk (2):
      xl: neuter vcpu-set --ignore-host.
      xl/vcpuset: Make it work for PV guests.