Hi, We encountered a vcpu-set issue on old xen, when I tried to confirm if xen upstream xen has the same issue I find neither my upstream build nor ubuntu 22.04 xen-hypervisor-4.16 work.
I can add vcpus(8->16) to my guest but I can not reduce vcpu number: root@ubuntu2204:~/vm# xl list Name ID Mem VCPUs State Time(s) Domain-0 0 255424 32 r----- 991.9 testvm 1 4088 16 -b---- 94.6 root@ubuntu2204:~/vm# xl vcpu-set testvm 8 root@ubuntu2204:~/vm# xl list Name ID Mem VCPUs State Time(s) Domain-0 0 255424 32 r----- 998.5 testvm 1 4088 16 -b---- 97.3 After xl vcpu-set, xenstore showed online cpu number reduced to 8: /local/domain/1/vm = "/vm/aa109ea0-2fde-4712-81d8-75f73bd73715" /local/domain/1/name = "testvm" /local/domain/1/cpu = "" /local/domain/1/cpu/0 = "" /local/domain/1/cpu/0/availability = "online" /local/domain/1/cpu/1 = "" /local/domain/1/cpu/1/availability = "online" /local/domain/1/cpu/2 = "" /local/domain/1/cpu/2/availability = "online" /local/domain/1/cpu/3 = "" /local/domain/1/cpu/3/availability = "online" /local/domain/1/cpu/4 = "" /local/domain/1/cpu/4/availability = "online" /local/domain/1/cpu/5 = "" /local/domain/1/cpu/5/availability = "online" /local/domain/1/cpu/6 = "" /local/domain/1/cpu/6/availability = "online" /local/domain/1/cpu/7 = "" /local/domain/1/cpu/7/availability = "online" /local/domain/1/cpu/8 = "" /local/domain/1/cpu/8/availability = "offline" /local/domain/1/cpu/9 = "" /local/domain/1/cpu/9/availability = "offline" /local/domain/1/cpu/10 = "" /local/domain/1/cpu/10/availability = "offline" /local/domain/1/cpu/11 = "" /local/domain/1/cpu/11/availability = "offline" /local/domain/1/cpu/12 = "" /local/domain/1/cpu/12/availability = "offline" /local/domain/1/cpu/13 = "" /local/domain/1/cpu/13/availability = "offline" /local/domain/1/cpu/14 = "" /local/domain/1/cpu/14/availability = "offline" /local/domain/1/cpu/15 = "" /local/domain/1/cpu/15/availability = "offline" /local/domain/1/cpu/16 = "" /local/domain/1/cpu/16/availability = "offline" But guest did not received any offline events at all. >From source code my understand is for cpu online, libxl will send device_add to qemu to trigger vcpu add, for cpu offline, it still rely on xenstore, is this correct? anything can block cpu scale down? Appreciate for any suggestions! Thanks, Joe
