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Description of Problem:

Any value that is out of range of cpu_shares can be specified.
virsh's man page says that a valid value range is 0-262144 for
cpu_shares. If an invalid value (e.g. -1) is specified when
"virsh schedinfo" is run, it changes the value to 262144 automatically.
In this case, "virsh schedinfo" shouldn't change the value, and should
report an error message like "cpu_shares is out of range". 


Version-Release number of selected component:

Red Hat Enterprise Linux Version Number: 6
Release Number: snapshot13
Architecture: x86_64
Kernel Version: kernel-2.6.32-70.el6.x86_64
Related Package Version: libvirt-client-0.8.1-27.el6.x86_64


How reproducible:
Always

Step to Reproduce:
1. Check that a guest OS is running.
# virsh list
Id Name State
----------------------------------
...
23 test01 running
...
<The guest "test01" is running.>


2. Change the cpu_shares to an invalid value.
# virsh schedinfo test01 --set cpu_shares=-1
Scheduler : posix
cpu_shares : 262144

Actual Results:
The value of cpu_shares is 262144 when an invalid value is specified.

Expected Results:
"virsh schedinfo" doesn't set 262144 to cpu_shares, and reports an
error message. 

--Humble

patch posted internally.

http://post-office.corp.redhat.com/archives/rhvirt-patches/2011-February/msg00019.html

I can reproduce the bug on rhel6.0 with libvirt-0.8.1-27.el6.x86_64, and the bug has been verified with libvirt-0.8.7-5.el6.x86_64 on rhel6 (2.6.32-113.el6.x86_64), and developers have improved virsh man page for this section:

Note: The cpu_shares parameter has a valid value range of 0-262144; Negative values are wrapped to positive, and larger values are capped at the maximum.  Therefore, -1 is a useful shorthand for 262144.

This is a documentation update, so that user could known for setting cpu.shares:

The cpu_shares parameter has a valid value range of 0-262144; Negative values are wrapped to positive, and larger values are capped at the maximum. Therefore, -1 is a useful shorthand for 262144.

We aleady documented this in virsh manual. (man virsh)

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-0596.html