On Mon, Sep 23, 2019 at 3:42 AM Dr. David Alan Gilbert <dgilb...@redhat.com> wrote: > > * Jintack Lim (incredible.t...@gmail.com) wrote: > > Hi, > > Copying in Paolo, since he recently did work to fix nested migration - > it was expected to be broken until pretty recently; but 4.1.0 qemu on > 5.3 kernel is pretty new, so I think I'd expected it to work. >
Thank you, Dave. What Paolo proposed make migration work! > > I'm seeing VM live migration failure when a VM is running a nested VM. > > I'm using latest Linux kernel (v5.3) and QEMU (v4.1.0). I also tried > > v5.2, but the result was the same. Kernel versions in L1 and L2 VM are > > v4.18, but I don't think that matters. > > > > The symptom is that L2 VM kernel crashes in different places after > > migration but the call stack is mostly related to memory management > > like [1] and [2]. The kernel crash happens almost all the time. While > > L2 VM gets kernel panic, L1 VM runs fine after the migration. Both L1 > > and L2 VM were doing nothing during migration. > > > > I found a few clues about this issue. > > 1) It happens with a relatively large memory for L1 (24G), but it does > > not with a smaller size (3G). > > > > 2) Dead migration worked; when I ran "stop" command in the qemu > > monitor for L1 first and did migration, migration worked always. It > > also worked when I only stopped L2 VM and kept L1 live during the > > migration. > > > > With those two clues, I guess maybe some dirty pages made by L2 are > > not transferred to the destination correctly, but I'm not really sure. > > > > 3) It happens on Intel(R) Xeon(R) Silver 4114 CPU, but it does not on > > Intel(R) Xeon(R) CPU E5-2630 v3 CPU. > > > > This makes me confused because I thought migrating nested state > > doesn't depend on the underlying hardware.. Anyways, L1-only migration > > with the large memory size (24G) works on both CPUs without any > > problem. > > > > I would appreciate any comments/suggestions to fix this problem. > > Can you share the qemu command lines you're using for both L1 and L2 > please ? Sure. I use the same QEMU command line for L1 and L2 except for cpu and memory allocation. This is the one for running L1, and I use smaller cpu and memory size for L2. ./qemu/x86_64-softmmu/qemu-system-x86_64 -smp 6 -m 24G -M q35,accel=kvm -cpu host -drive if=none,file=/vm_nfs/guest0.img,id=vda,cache=none,format=raw -device virtio-blk-pci,drive=vda --nographic -qmp unix:/var/run/qmp,server,wait -serial mon:stdio -netdev user,id=net0,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=net0,mac=de:ad:be:ef:f2:12 -netdev tap,id=net1,vhost=on,helper=/srv/vm/qemu/qemu-bridge-helper -device virtio-net-pci,netdev=net1,disable-modern=off,disable-legacy=on,mac=de:ad:be:ef:f2:11 -monitor telnet:127.0.0.1:4444,server,nowait > Are there any dmesg entries around the time of the migration on either > the hosts or the L1 VMs? No, I didn't see anything special in L0 or L1 kernel log. > What guest OS are you running in L1 and L2? > I'm using Linux v4.18 both in L1 and L2. Thanks, Jintack > Dave > > > Thanks, > > Jintack > > > > > > [1]https://paste.ubuntu.com/p/XGDKH45yt4/ > > [2]https://paste.ubuntu.com/p/CpbVTXJCyc/ > > > -- > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
