Hi, We know that there is a command "setvcpus" in virsh used to "change number of virtual CPUs", now we just have the need to change vcpu count dynamically for a running VM, so I tried this command (the vcpu count is 2 in the VM xml file), below is the result: virsh # setvcpus 3 --count 4 error: invalid argument: requested vcpus is greater than max allowable vcpus for the domain: 4 > 2 virsh # setvcpus 3 --count 1 error: Operation not supported: qemu didn't unplug the vCPUs properly So I tried another way: log into the running VM, and "echo 0 > /sys/devices/system/cpu/cpu1/online", after that I can find only one processor in the vm through '/proc/cpuinfo', but in virsh, the vcpuinfo still shows: virsh # vcpuinfo 3 VCPU: 0 CPU: 0 State: running CPU time: 13.5s CPU Affinity: yyyy VCPU: 1 CPU: 1 State: running CPU time: 6.9s CPU Affinity: yyyy So the question is: is there any method I can't find yet to change the vcpu count of a running vm dynamically? BRs, Dennis