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(In reply to Fangge Jin from comment #0)
>
> 3.Compare the qemu command line between source host and target host, they
> are different.
> Source host:
> -object
> memory-backend-file,id=ram-node0,mem-path=/var/lib/libvirt/qemu/ram,
> size=536870912 -numa node,nodeid=0,cpus=0-7,memdev=ram-node0 -object
> memory-backend-file,id=ram-node1,mem-path=/var/lib/libvirt/qemu/ram,
> size=536870912
>
> Target host:
> -object
> memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/
> libvirt/qemu/1-rhel7.4,size=536870912 -numa
> node,nodeid=0,cpus=0-7,memdev=ram-node0 -object
> memory-backend-file,id=ram-node1,prealloc=yes,mem-path=/dev/hugepages/
> libvirt/qemu/1-rhel7.4,size=536870912
>
The problem is not hugepages + file combination per se, but the fact that due to bug 1214369 libvirt preferred source='file' over hugepages. In fix for bug 1214369 the preference was fixed and therefore with never versions libvirt chooses hugepages. However, migration is broken.
I don't think there is much we can do here. Anyway, I am sending a patch that explicitly forbids this nonsensical combination at define time:
https://www.redhat.com/archives/libvir-list/2018-October/msg00794.html
The upstream is not in favour of the patches. Truth to be told, I am not much convinced myself. Originally, the misconfiguration should have been declined in 7.4 but that ship sailed long time ago. As I said earlier, I don't think there is much we can do.
Fangge, what are your thoughts? I'm inclined to close this as WONTFIX/CANTFIX.
(In reply to Michal Privoznik from comment #5)
> The upstream is not in favour of the patches. Truth to be told, I am not
> much convinced myself. Originally, the misconfiguration should have been
> declined in 7.4 but that ship sailed long time ago. As I said earlier, I
> don't think there is much we can do.
>
> Fangge, what are your thoughts? I'm inclined to close this as
> WONTFIX/CANTFIX.
I agree with you to close it if there is nothing we can do. As long as no customer meets this issue, it is not a problem
Description of problem: VM with "hugepage" + "file backend memory" fails to migrate from RHEL7.4 to RHEL7.6 Version-Release number of selected component (if applicable): RHEL7.6 libvirt-4.5.0-10.el7.x86_64 qemu-kvm-rhev-2.12.0-18.el7.x86_64 kernel-3.10.0-944.el7.x86_64 RHEL7.4 libvirt-3.2.0-14.el7_4.12.x86_64 qemu-kvm-rhev-2.9.0-16.el7_4.18.x86_64 kernel-3.10.0-693.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1.Prepare a guest on RHEL7.4 host with hugepage+file backend memory: # virsh dumpxml rhel7.4 ... <memoryBacking> <hugepages/> <nosharepages/> <source type='file'/> </memoryBacking> ... 2.Start guest, migrate it to RHEL7.6 host with postcopy: # virsh migrate rhel7.4 qemu+ssh://192.168.122.225/system --live --verbose --postcopy --postcopy-after-precopy error: internal error: qemu unexpectedly closed the monitor: 2018-09-27T09:48:01.014059Z qemu-kvm: Postcopy needs matching RAM page sizes (s=1000 d=201000) 2018-09-27T09:48:01.016917Z qemu-kvm: load of migration failed: Operation not permitted 3.Compare the qemu command line between source host and target host, they are different. Source host: -object memory-backend-file,id=ram-node0,mem-path=/var/lib/libvirt/qemu/ram,size=536870912 -numa node,nodeid=0,cpus=0-7,memdev=ram-node0 -object memory-backend-file,id=ram-node1,mem-path=/var/lib/libvirt/qemu/ram,size=536870912 Target host: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/1-rhel7.4,size=536870912 -numa node,nodeid=0,cpus=0-7,memdev=ram-node0 -object memory-backend-file,id=ram-node1,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/1-rhel7.4,size=536870912 Actual results: Migration fails Expected results: Migration succeeds. Additional info: