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    Live migrate of Rocky Linux 8.8 VM crashes/reboots VM

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    • olivierlambertO
      olivierlambert Vates 🪐 Co-Founder CEO
      last edited by

      Hi,

      We managed to reproduce the issue. We are investigating, thinking on a bug on 8.8 or a component inside it.

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      • W
        Weppel @olivierlambert
        last edited by

        @olivierlambert Thank you very much for the quick follow-up.

        I've done some testing with a colleague and it looks to be kernel related. The stock Rocky Linux 8.8 kernel (4.18.0-477.13.1.el8_8.x86_64) causes the reboot to happen. Upgrading the kernel to kernel-lt (5.4.245-1.1.el8.elrepo.x86_64) allows the VM to be live-migrated again without reboot/crash.

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        • olivierlambertO
          olivierlambert Vates 🪐 Co-Founder CEO
          last edited by

          Thanks for the investigation. I think that might worth an upstream report to Rocky, right?

          W 1 Reply Last reply Reply Quote 0
          • B
            bogikornel
            last edited by olivierlambert

            I had the same problem with Oracle Linux 8. Kernel versions: 4.18.0-477.10 or 4.18.0-477.13.
            Previous kernel series, and UEK kernel, no such problem.

            This is what I saw in the log:

            Jun 8 09:40:31 gpool05-nodeA xenopsd-xc: [error||4030359 ||backtrace] Connection to VM console R:a08260fac6a2 failed, exception Xenops_interface.Xenopsd_error([S(Does_not_exist);[S(VM);S(87b062dd-b53f-04d7-c49d-32deec6716d6/config)]])
Jun 8 09:40:31 gpool05-nodeA xenopsd-xc: [error||4030359 ||backtrace] Raised Xenops_interface.Xenopsd_error([S(Does_not_exist);[S(VM);S(87b062dd-b53f-04d7-c49d-32deec6716d6/config)]])
Jun 8 09:40:31 gpool05-nodeA xenopsd-xc: [error||4030359 ||xenops_interface] Xenops_interface.Xenopsd_error([S(Does_not_exist);[S(VM);S(87b062dd-b53f-04d7-c49d-32deec6716d6/config)]]) (File "xen/xenops_interface.ml", line 165, characters 51-58)
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            • W
              Weppel @olivierlambert
              last edited by

              @olivierlambert

              I've created a bug report at Rocky Linux: https://bugs.rockylinux.org/view.php?id=3565

              Feel free to add to this if I missed any relevant information.

              stormiS 1 Reply Last reply Reply Quote 1
              • stormiS
                stormi Vates 🪐 XCP-ng Team @Weppel
                last edited by

                @Weppel It looks like you wrote KVM instead of Xen in the title.

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                • W
                  Weppel @stormi
                  last edited by

                  @stormi Thanks for noticing, my bad

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                  • stormiS
                    stormi Vates 🪐 XCP-ng Team
                    last edited by

                    Adding @bleader to the discussion. He's trying to debug the issue.

                    It looks like a simple VM suspend + resume also crashes the VM. Do you confirm, @Weppel?

                    W 1 Reply Last reply Reply Quote 0
                    • W
                      Weppel @stormi
                      last edited by

                      @stormi Confirmed

                      1 Reply Last reply Reply Quote 3
                      • bleaderB
                        bleader Vates 🪐 XCP-ng Team
                        last edited by

                        So, after our investigations, we were able to pinpoint the issue.

                        It seem to happen on most RHEL derivative distributions when migrating from 8.7 to 8.8. As suggested, the bug is in the kernel.

                        Starting with 4.18.0-466.el8 the patch: x86/idt: Annotate alloc_intr_gate() with __init is integrated and will create the issue. It is missing x86/xen: Split HVM vector callback setup and interrupt gate allocation that should have been integrated as well.

                        The migration to 8.8 will move you to 4.18.0-477.* versions that are also raising this issue, that's what you reported.

                        We found that the 4.18.0-488 that can be found in CentOS 8 Stream integrates the missing patch, and do indeed work when installed manually.

                        Your report helped us identify and reproduce the issues. That allowed us to provide a callstack to Xen devs. Then Roger Pau Monné found that it was this patch missing quickly, and we were able to find which versions of the kernel RPMs were integrating it and when the fix was integrated.

                        This means the issue was identified on RH side, and it is now a matter of having an updated kernel in derivative distributions like Rocky and Alma.

                        W 1 Reply Last reply Reply Quote 3
                        • W
                          Weppel @bleader
                          last edited by

                          @bleader Thank you very much for the quick discovery of this, impressive work! I'm glad I could help!

                          1 Reply Last reply Reply Quote 2
                          • olivierlambertO olivierlambert marked this topic as a question on
                          • olivierlambertO olivierlambert has marked this topic as solved on
                          • W
                            Weppel
                            last edited by

                            FYI this is not fixed yet in the latest EL kernel 4.18.0-477.15.1.el8_8.x86_64

                            1 Reply Last reply Reply Quote 1
                            • olivierlambertO
                              olivierlambert Vates 🪐 Co-Founder CEO
                              last edited by

                              Thanks for keeping us posted…

                              Hopefully things will be fixed at some point. Maybe Red Hat is focused on doing other things right now…

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                              • bleaderB
                                bleader Vates 🪐 XCP-ng Team
                                last edited by

                                Makes sense, I was hoping they would go with a -488 on update... Sorry to hear its not the case 😞

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                                • Q
                                  qnx @bleader
                                  last edited by

                                  @bleader Unfortunately, I think we're stuck on -477 until EL 8.9 comes out 😕

                                  it's frustrating that it's taking them so long to fix this, especially when it seems like the bug was caused by a human error to begin with.

                                  1 Reply Last reply Reply Quote 0
                                  • bleaderB
                                    bleader Vates 🪐 XCP-ng Team
                                    last edited by

                                    Not entirely sure, but that may be related to what's happening on redhat side of things 😕

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                                    • K
                                      KFC-Netearth
                                      last edited by

                                      Just installed the latest kernel from Rocky and a live migrate seems to work on the 2 dev servers I have tried so far :
                                      4.18.0-477.21.1.el8_8.x86_64 #1 SMP Tue Aug 8 21:30:09 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

                                      bleaderB W 2 Replies Last reply Reply Quote 1
                                      • bleaderB
                                        bleader Vates 🪐 XCP-ng Team @KFC-Netearth
                                        last edited by

                                        @KFC-Netearth Surprising as it is still .477 but maybe the patch was backported, thanks for telling us!

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                                        • W
                                          Weppel @KFC-Netearth
                                          last edited by

                                          @KFC-Netearth

                                          The Rocky Linux bugtracker indeed mentions it's mostly fixed, but there are still some kernel errors present: https://bugs.rockylinux.org/view.php?id=3565#c4293

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