It was a bit strange that the jammy 5.15 kernel worked on the v6 instance type, so I also went and verified for 6.8 on jammy HWE.
Performing verification for jammy HWE. I created two VMs on Azure, one of each: - Standard_D4ads_v5 - Standard_D4ads_v6 using the - "Ubuntu Server 22.04 LTS - x64 Gen2" image. On each instance I turned off Secure Boot. Each VM is running 6.8.0-1062-azure from -updates. $ uname -rv 6.8.0-1062-azure #69~22.04.1-Ubuntu SMP Mon Jun 29 19:32:04 UTC 2026 I installed kdump-tools, configured the modules to include in the initramfs, and rebooted. From there I opened the serial console on Azure, and crashed the VM with sysrq trigger. The v6 instance gets stuck during kexec boot. Looking through the serial console I see: [ 0.769578] hv_vmbus: registering driver hv_pci [ 0.775870] hv_pci 7ad35d50-c05b-47ab-b3a0-56a9a845852b: PCI VMBus probing: Using version 0x10004 [ 0.785099] hv_pci 7ad35d50-c05b-47ab-b3a0-56a9a845852b: Retrying D0 Entry [ 0.790771] hv_pci 7ad35d50-c05b-47ab-b3a0-56a9a845852b: PCI Pass-through VSP failed D0 Entry with status c0370048 [ 0.800755] hv_vmbus: probe failed for device 7ad35d50-c05b-47ab-b3a0-56a9a845852b (-71) [ 0.804779] hv_pci: probe of 7ad35d50-c05b-47ab-b3a0-56a9a845852b failed with error -71 [ 0.819251] hv_pci 4fa6bdc7-d125-4935-9ade-79c121171051: PCI VMBus probing: Using version 0x10004 [ 0.828004] hv_pci 4fa6bdc7-d125-4935-9ade-79c121171051: Retrying D0 Entry [ 0.850997] hv_pci 4fa6bdc7-d125-4935-9ade-79c121171051: PCI Pass-through VSP failed D0 Entry with status c0370048 [ 0.862687] hv_vmbus: probe failed for device 4fa6bdc7-d125-4935-9ade-79c121171051 (-71) [ 0.866584] hv_pci: probe of 4fa6bdc7-d125-4935-9ade-79c121171051 failed with error -71 [ 0.881378] hv_pci 7b105564-b004-45ec-aba6-6637afa95dde: PCI VMBus probing: Using version 0x10004 [ 0.891098] hv_pci 7b105564-b004-45ec-aba6-6637afa95dde: Retrying D0 Entry [ 0.897780] hv_pci 7b105564-b004-45ec-aba6-6637afa95dde: PCI Pass-through VSP failed D0 Entry with status c0370048 [ 0.908555] hv_vmbus: probe failed for device 7b105564-b004-45ec-aba6-6637afa95dde (-71) [ 0.912513] hv_pci: probe of 7b105564-b004-45ec-aba6-6637afa95dde failed with error -71 [ 0.919503] Freeing initrd memory: 32556K and also [ 1.470430] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] Synthvid Version major 3, minor 5 [ 1.472227] hv_vmbus: registering driver hv_netvsc [ 1.472906] hv_vmbus: registering driver hyperv_keyboard [ 1.473890] [drm] Initialized hyperv_drm 1.0.0 2020 for 5620e0c7-8062-4dce-aeb7-520c7ef76171 on minor 0 [ 1.479156] Console: switching to colour frame buffer device 128x48 [ 1.479656] input: AT Translated Set 2 keyboard as /devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0004:00/MSFT1000:00/d34b2567-b9b6-42b9-8778-0a4ec0b955bf/serio0/input/input0 [ 1.485556] hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] fb0: hyperv_drmdrmfb frame buffer device [ 1.488192] hv_vmbus: registering driver hid_hyperv [ 1.495582] input: Microsoft Vmbus HID-compliant Mouse as /devices/0006:045E:0621.0001/input/input1 [ 1.497750] hid-hyperv 0006:045E:0621.0001: input: VIRTUAL HID v0.01 Mouse [Microsoft Vmbus HID-compliant Mouse] on [ 1.508783] hv_netvsc 002248e2-f81d-0022-48e2-f81d002248e2 (unnamed net_device) (uninitialized): VF slot 1 added Begin: Loading essential drivers ... [ 1.627869] rdac: device handler registered It seems that hyperv_drm wins access to the MMIO range, and hv_pci gets left out in the cold. Which tracks, because I get no rootfs, and no kdump is captured. When I log into the system, there is no kdump in /var/crash. The v5 system correctly captures the kdump. I then enabled the kernel team ppa, since linux-azure-6.8 is not in -proposed yet, and installed the 6.8.0-1063-azure kernel and rebooted. $ uname -rv 6.8.0-1063-azure #71~22.04.1-Ubuntu SMP Mon Jul 6 22:48:31 UTC 2026 From there I repeated the same crashdump collection. Both the v5 and v6 instances correctly collected a crashdump and wrote it to /var/crash. There does not appear to be any regressions on v5. It solves the problem on v6, and v6 can crashdump correctly now. Marking verified for jammy HWE. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2155222 Title: [hyperv] Ensure MMIO Mapping is Correct for Kexec / kdump kernel on Azure v6 Instance Types To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/2155222/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
