These values shouldn't be negative, but after an overflow their value
can turn into negative, if they are signed. xentop can show bogus
values in this case.
Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: Ichiro Ogino <ichiro.ogino@citrix.co.jp>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>