[libvirt] [BUG] pinvcpu before migration

[Wangyufei (James)]

hi , I am confused by pinvcpu before migration.

I have two physical machine. One has 12 CPUs (E5645 2*6 ) as src and the other has 8 CPUs (2*4) as des.

Step 1 : VM is running on src host (E5645 2*6 CPUs) with its VCPUs pinned on some PCPUs

Step 2 :Because PCPU count is different between src and des , I should pin VCPUs to all PCPUs .  
        virsh vcpupin vmname 0 0-11 --config --live

Step 3: Do migrate ,and it failed with error in des libvirt log "Unable to set cpuset.cpus: Invalid argument"

I find that VM's cpu bitmap on src turns to <vcpupin vcpu='0' cpuset='0-11'/> . vm start fails on des due to its pin info cpuset='0-11' in vm->def.

In usual case, after I pin VCPU to all PCPU, vcpupin info will be deleted in vm->def.

-- qemuDomainPinVcpuFlags
  -- if (virBitmapIsAllSet(pcpumap, pCpuCount))
        doReset = true; 
  -- if (doReset) 
        if (virDomainVcpuPinDel(vm->def, vcpu) < 0)


I debug libvirt and find that on src which PCPU count is 12 (2*6) virBitmapIsAllSet(pcpumap, pCpuCount) return false

pcpumap->max_bit is 16.   pcpumap = virBitmapNewData(cpumap, maplen) --> bitmap = virBitmapNew(len * CHAR_BIT);  //here len is 2.

Although my physical machine only has 12 PCPUs , but here pcpumap->max_bit is len*CHAR_BIT . So bitmap is 0000 1111 1111 1111 ,and it's not ALL SET (ALL SET is 1111 1111 1111 1111).

I tried to fix the bug in this case , but I have not found a good solution.

Any suggestions will be thankful.

Best Regards,
-WangYufei