[libvirt] Question : Configuring a VM with backing 1G huge pages across 2 NUMA nodes

Hi Michal, 'have a kernel+qemu+libvirt setup with all recent upstream bits on a given host & was trying to configure a VM with backing 1G huge pages...spanning 2 NUMA nodes. The host had 3 1G huge pages on each of the 2 NUMA nodes : # cat /sys/devices/system/node/node0/hugepages/hugepages-1048576kB/nr_hugepages 3 # cat /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepages 3 And I had the following in the /etc/fstab hugetlbfs /hugepages_1G hugetlbfs pagesize=1GB 0 0 I added the following entries in the xml file for the 4G/4vcpu VM <memoryBacking> <hugepages> <page size='1048576' unit='KiB' nodeset='0'/> <page size='1048576' unit='KiB' nodeset='1'/> </hugepages> </memoryBacking> <vcpu placement='static'>4</vcpu> <cputune> <vcpupin vcpu='0' cpuset='0'/> <vcpupin vcpu='1' cpuset='1'/> <vcpupin vcpu='2' cpuset='8'/> <vcpupin vcpu='3' cpuset='9'/> </cputune> .... <numatune> <memory node="strict" nodeset="0-1"/> </numatune> .... <cpu> <numa> <cell id='0' cpus='0-1' memory='2097152'/> <cell id='1' cpus='2-3' memory='2097152'/> </numa> </cpu> The resulting qemu command looked like this : /usr/local/bin/qemu-system-x86_64 -name vm1 -S -machine pc-i440fx-2.2,accel=kvm,usb=off \ -m 4096 -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 \ -object memory-backend-file,prealloc=yes,mem-path=/hugepages_1G/libvirt/qemu,size=2048M,id=ram-node0,host-nodes=0-1,policy=bind -numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \ -object memory-backend-file,prealloc=yes,mem-path=/hugepages_1G/libvirt/qemu,size=2048M,id=ram-node1,host-nodes=0-1,policy=bind -numa node,nodeid=1,cpus=2-3,memdev=ram-node1 \ .... There were 3 1G pages available on each NUMA node on the host as shown above... and I noticed that the VM got backed by 3 1G pages from node0 and 1 1G page from node1. #cat /sys/devices/system/node/node0/hugepages/hugepages-1048576kB/free_hugepages 0 # cat /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/free_hugepages 2 Not sure if this was expected behavior given the options I specified in the xml file ? If yes...Is there some additional option to specify (in the XML file) such that only a given number of 1Gig huge pages per node are picked to back the VM (i.e. in the above case just 2 1G from each node) ? Thanks! Vinod