* 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.
> 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 ? Are there any dmesg entries around the time of the migration on either the hosts or the L1 VMs? What guest OS are you running in L1 and L2? 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
