Why does xen guest detect / show lesser number of vcpus than the configured value ?

Issue

• The xen guests detects less number of cpus .
• Why does xen guest show 6 cpus instead of 8 ?

xm vcpu-list kvm-guest1
Name                              ID VCPUs   CPU State   Time(s) CPU Affinity
kvm-guest1                           3     0     6   -b-   69706.6 any cpu
kvm-guest1                           3     1    11   -b-   20613.4 any cpu
kvm-guest1                           3     2     8   -b-   18199.8 any cpu
kvm-guest1                           3     3     1   -b-   17999.1 any cpu
kvm-guest1                           3     4     0   -b-   17936.6 any cpu
kvm-guest1                           3     5     9   -b-   18011.2 any cpu
kvm-guest1                           3     6     -   --p       0.0 any cpu
kvm-guest1                           3     7     -   --p       0.0 any cpu