Peter Morrow reported in Debian a regression, reported in https://bugs.debian.org/1120602 . The regression was seen after updating, to 6.12.57-1 in Debian, but details on the offending commit follows.
His report was as follows:
Dear Maintainer,
I'm seeing a kernel crash quite soon after boot on a debian trixie based system running 6.12.57+deb13-amd64, unfortunately the kernel panics before I can access the system to gather more information. Thus I'll provide details of the system using a previously known good version. The panic is happening 100% of the time unfortunately. I have access to the serial console however so can enable any required verbose logging during boot if necessary.
Crucially the crash is not seen with kernel version 6.12.41+deb13-amd64 with the same userspace. We had pinned to that version until very recently to in order to work around https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1109676
I'm running a dpdk application here (VPP) on Azure, VM form factor is a "Standard DS3 v2 (4 vcpus, 14 GiB memory)".
The only relevant upstream commit in this area (as far as I can see) is:
https://lore.kernel.org/linux-hyperv/1bb599ee-fe28-409d-b430-2fc086268936@li...
The comment regarding avoiding races at start adds a bit more weight behind this hunch, though it's only a hunch as I am most definitely nowhere near an expert in this area.
-- Package-specific info:
[ 19.625535] BUG: kernel NULL pointer dereference, address: 00000000000000a0 [ 19.628874] #PF: supervisor read access in kernel mode [ 19.630841] #PF: error_code(0x0000) - not-present page [ 19.632788] PGD 0 P4D 0 [ 19.633905] Oops: Oops: 0000 [#1] PREEMPT SMP PTI [ 19.635586] CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.12.57+deb13-amd64 #1 Debian 6.12.57-1 [ 19.640216] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 09/28/2024 [ 19.644514] RIP: 0010:hv_uio_channel_cb+0xd/0x20 [uio_hv_generic] [ 19.646994] Code: 02 00 00 5b 5d e9 53 98 69 e9 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 47 10 <48> 8b b8 a0 00 00 00 f0 83 44 24 fc 00 e9 51 6f fa ff 90 90 90 90 [ 19.654377] RSP: 0018:ffffb15ac01a4fa8 EFLAGS: 00010046 [ 19.656385] RAX: 0000000000000000 RBX: 0000000000000015 RCX: 0000000000000015 [ 19.659240] RDX: 0000000000000001 RSI: ffffffffffffffff RDI: ffff8ff69c759400 [ 19.662168] RBP: ffff8ff548790200 R08: ffff8ff548790200 R09: 00fca75150b080e9 [ 19.665239] R10: 0000000000000000 R11: ffffb15ac01a4ff8 R12: ffff8ff871dc1480 [ 19.668193] R13: ffff8ff69c759400 R14: ffff8ff69c7596a0 R15: ffffffffc106e160 [ 19.671106] FS: 0000000000000000(0000) GS:ffff8ff871d80000(0000) knlGS:0000000000000000 [ 19.674281] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 19.676533] CR2: 00000000000000a0 CR3: 0000000100ba6003 CR4: 00000000003706f0 [ 19.679385] Call Trace: [ 19.680361] <IRQ> [ 19.681181] vmbus_isr+0x1a5/0x210 [hv_vmbus] [ 19.682916] __sysvec_hyperv_callback+0x32/0x60 [ 19.684991] sysvec_hyperv_callback+0x6c/0x90 [ 19.686665] </IRQ> [ 19.687509] <TASK> [ 19.688366] asm_sysvec_hyperv_callback+0x1a/0x20 [ 19.690262] RIP: 0010:pv_native_safe_halt+0xf/0x20 [ 19.692067] Code: 09 e9 c5 08 01 00 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d e5 3b 31 00 fb f4 <c3> cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 [ 19.699119] RSP: 0018:ffffb15ac0103ed8 EFLAGS: 00000246 [ 19.701412] RAX: 0000000000000003 RBX: ffff8ff5403b1fc0 RCX: ffff8ff54c64ce30 [ 19.704328] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 000000000001f894 [ 19.706910] RBP: 0000000000000003 R08: 000000000bb760d9 R09: 00fca75150b080e9 [ 19.709762] R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000000 [ 19.712510] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 19.715173] default_idle+0x9/0x20 [ 19.716846] default_idle_call+0x29/0x100 [ 19.718623] do_idle+0x1fe/0x240 [ 19.720045] cpu_startup_entry+0x29/0x30 [ 19.721595] start_secondary+0x11e/0x140 [ 19.723080] common_startup_64+0x13e/0x141 [ 19.725222] </TASK> [ 19.726387] Modules linked in: isofs cdrom uio_hv_generic uio binfmt_misc intel_rapl_msr intel_rapl_common intel_uncore_frequency_common isst_if_mbox_msr isst_if_common rpcrdma skx_edac_common nfit sunrpc libnvdimm crct10dif_pclmul ghash_clmulni_intel sha512_ssse3 sha256_ssse3 rdma_ucm ib_iser sha1_ssse3 rdma_cm aesni_intel iw_cm gf128mul crypto_simd libiscsi cryptd ib_umad ib_ipoib scsi_transport_iscsi ib_cm rapl sg hv_utils hv_balloon evdev pcspkr joydev mpls_router ip_tunnel ramoops configfs pstore_blk efi_pstore pstore_zone nfnetlink vsock_loopback vmw_vsock_virtio_transport_common hv_sock vmw_vsock_vmci_transport vsock vmw_vmci efivarfs ip_tables x_tables autofs4 overlay squashfs dm_verity dm_bufio reed_solomon dm_mod loop ext4 crc16 mbcache jbd2 crc32c_generic mlx5_ib ib_uverbs ib_core mlx5_core mlxfw pci_hyperv pci_hyperv_intf hyperv_drm drm_shmem_helper sd_mod drm_kms_helper hv_storvsc scsi_transport_fc drm scsi_mod hid_generic hid_hyperv hid serio_raw hv_netvsc hyperv_keyboard scsi_common hv_vmbus [ 19.726466] crc32_pclmul crc32c_intel [ 19.765771] CR2: 00000000000000a0 [ 19.767524] ---[ end trace 0000000000000000 ]--- [ 19.800433] RIP: 0010:hv_uio_channel_cb+0xd/0x20 [uio_hv_generic] [ 19.803170] Code: 02 00 00 5b 5d e9 53 98 69 e9 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 47 10 <48> 8b b8 a0 00 00 00 f0 83 44 24 fc 00 e9 51 6f fa ff 90 90 90 90 [ 19.811041] RSP: 0018:ffffb15ac01a4fa8 EFLAGS: 00010046 [ 19.813466] RAX: 0000000000000000 RBX: 0000000000000015 RCX: 0000000000000015 [ 19.816504] RDX: 0000000000000001 RSI: ffffffffffffffff RDI: ffff8ff69c759400 [ 19.819484] RBP: ffff8ff548790200 R08: ffff8ff548790200 R09: 00fca75150b080e9 [ 19.822625] R10: 0000000000000000 R11: ffffb15ac01a4ff8 R12: ffff8ff871dc1480 [ 19.825569] R13: ffff8ff69c759400 R14: ffff8ff69c7596a0 R15: ffffffffc106e160 [ 19.828804] FS: 0000000000000000(0000) GS:ffff8ff871d80000(0000) knlGS:0000000000000000 [ 19.832214] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 19.834709] CR2: 00000000000000a0 CR3: 0000000100ba6003 CR4: 00000000003706f0 [ 19.837976] Kernel panic - not syncing: Fatal exception in interrupt [ 19.841825] Kernel Offset: 0x28a00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 19.896620] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
lspci output:
Collected from a system that is not crashing (6.12.41+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.41-1 (2025-08-12) x86_64 GNU/Linux)...
$ sudo lspci -v 2f22:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function] (rev 80) Subsystem: Mellanox Technologies Device 0190 Physical Slot: 3 Flags: bus master, fast devsel, latency 0, NUMA node 0 Memory at fe0100000 (64-bit, prefetchable) [size=1M] Capabilities: [60] Express Endpoint, IntMsgNum 0 Capabilities: [9c] MSI-X: Enable+ Count=8 Masked- Kernel driver in use: mlx5_core Kernel modules: mlx5_core
52f7:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function] (rev 80) Subsystem: Mellanox Technologies Device 0190 Physical Slot: 2 Flags: bus master, fast devsel, latency 0, NUMA node 0 Memory at fe0000000 (64-bit, prefetchable) [size=1M] Capabilities: [60] Express Endpoint, IntMsgNum 0 Capabilities: [9c] MSI-X: Enable+ Count=8 Masked- Kernel driver in use: mlx5_core Kernel modules: mlx5_core
7852:00:02.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function] (rev 80) Subsystem: Mellanox Technologies Device 0190 Physical Slot: 4 Flags: bus master, fast devsel, latency 0, NUMA node 0 Memory at fe0200000 (64-bit, prefetchable) [size=1M] Capabilities: [60] Express Endpoint, IntMsgNum 0 Capabilities: [9c] MSI-X: Enable+ Count=8 Masked- Kernel driver in use: mlx5_core Kernel modules: mlx5_core
dmidecode output:
$ sudo dmidecode # dmidecode 3.6 Getting SMBIOS data from sysfs. SMBIOS 3.1.0 present. Table at 0x3FF82000.
Handle 0x0000, DMI type 0, 26 bytes BIOS Information Vendor: Microsoft Corporation Version: Hyper-V UEFI Release v4.1 Release Date: 05/13/2024 ROM Size: 64 kB Characteristics: BIOS characteristics not supported ACPI is supported Targeted content distribution is supported UEFI is supported System is a virtual machine BIOS Revision: 4.1
Handle 0x0001, DMI type 1, 27 bytes System Information Manufacturer: Microsoft Corporation Product Name: Virtual Machine Version: Hyper-V UEFI Release v4.1 Serial Number: 0000-0010-5437-9499-5225-4477-46 UUID: 925315af-4af4-4d42-915a-1516b5a1fe5c Wake-up Type: Power Switch SKU Number: None Family: Virtual Machine
Handle 0x0002, DMI type 3, 24 bytes Chassis Information Manufacturer: Microsoft Corporation Type: Desktop Lock: Not Present Version: Hyper-V UEFI Release v4.1 Serial Number: 2466-9316-1078-9783-6078-7718-80 Asset Tag: 7783-7084-3265-9085-8269-3286-77 Boot-up State: Safe Power Supply State: Safe Thermal State: Safe Security Status: Unknown OEM Information: 0x00000000 Height: Unspecified Number Of Power Cords: Unspecified Contained Elements: 0 SKU Number: Virtual Machine
Handle 0x0003, DMI type 2, 17 bytes Base Board Information Manufacturer: Microsoft Corporation Product Name: Virtual Machine Version: Hyper-V UEFI Release v4.1 Serial Number: 0000-0010-4737-0707-0684-2660-76 Asset Tag: None Features: Board is a hosting board Location In Chassis: Virtual Machine Chassis Handle: 0x0002 Type: Motherboard Contained Object Handles: 0
Handle 0x0004, DMI type 4, 48 bytes Processor Information Socket Designation: None Type: Central Processor Family: Unknown Manufacturer: None ID: 00 00 00 00 00 00 00 00 Version: None Voltage: Unknown External Clock: Unknown Max Speed: Unknown Current Speed: Unknown Status: Unpopulated Upgrade: Other L1 Cache Handle: Not Provided L2 Cache Handle: Not Provided L3 Cache Handle: Not Provided Serial Number: None Asset Tag: None Part Number: None Core Count: 4 Core Enabled: 4 Thread Count: 1 Characteristics: None
Handle 0x0005, DMI type 11, 5 bytes OEM Strings String 1: [MS_VM_CERT/SHA1/9b80ca0d5dd061ec9da4e494f4c3fd1196270c22] String 2: None String 3: To be filled by OEM
Handle 0x0006, DMI type 16, 23 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: None Maximum Capacity: 0 bytes Error Information Handle: Not Provided Number Of Devices: 3
Handle 0x0007, DMI type 17, 92 bytes Memory Device Array Handle: 0x0006 Error Information Handle: Not Provided Total Width: Unknown Data Width: Unknown Size: 26 MB Form Factor: Unknown Set: None Locator: M0001 Bank Locator: None Type: Unknown Type Detail: Unknown Speed: Unknown Manufacturer: Microsoft Corporation Serial Number: None Asset Tag: None Part Number: None Rank: Unknown Configured Memory Speed: Unknown Minimum Voltage: Unknown Maximum Voltage: Unknown Configured Voltage: Unknown Memory Technology: <OUT OF SPEC> Memory Operating Mode Capability: None Firmware Version: Not Specified Module Manufacturer ID: Unknown Module Product ID: Unknown Memory Subsystem Controller Manufacturer ID: Unknown Memory Subsystem Controller Product ID: Unknown Non-Volatile Size: None Volatile Size: None Cache Size: None Logical Size: None
Handle 0x0008, DMI type 19, 31 bytes Memory Array Mapped Address Starting Address: 0x00000000000 Ending Address: 0x00001A003FF Range Size: 26625 kB Physical Array Handle: 0x0006 Partition Width: 0
Handle 0x0009, DMI type 20, 35 bytes Memory Device Mapped Address Starting Address: 0x00000000000 Ending Address: 0x00001A003FF Range Size: 26625 kB Physical Device Handle: 0x0007 Memory Array Mapped Address Handle: 0x0008 Partition Row Position: Unknown
Handle 0x000A, DMI type 17, 92 bytes Memory Device Array Handle: 0x0006 Error Information Handle: Not Provided Total Width: Unknown Data Width: Unknown Size: 948 MB Form Factor: Unknown Set: None Locator: M0002 Bank Locator: None Type: Unknown Type Detail: Unknown Speed: Unknown Manufacturer: Microsoft Corporation Serial Number: None Asset Tag: None Part Number: None Rank: Unknown Configured Memory Speed: Unknown Minimum Voltage: Unknown Maximum Voltage: Unknown Configured Voltage: Unknown Memory Technology: <OUT OF SPEC> Memory Operating Mode Capability: None Firmware Version: Not Specified Module Manufacturer ID: Unknown Module Product ID: Unknown Memory Subsystem Controller Manufacturer ID: Unknown Memory Subsystem Controller Product ID: Unknown Non-Volatile Size: None Volatile Size: None Cache Size: None Logical Size: None
Handle 0x000B, DMI type 19, 31 bytes Memory Array Mapped Address Starting Address: 0x00004C00000 Ending Address: 0x000400003FF Range Size: 970753 kB Physical Array Handle: 0x0006 Partition Width: 0
Handle 0x000C, DMI type 20, 35 bytes Memory Device Mapped Address Starting Address: 0x00004C00000 Ending Address: 0x000400003FF Range Size: 970753 kB Physical Device Handle: 0x000A Memory Array Mapped Address Handle: 0x000B Partition Row Position: Unknown
Handle 0x000D, DMI type 17, 92 bytes Memory Device Array Handle: 0x0006 Error Information Handle: Not Provided Total Width: Unknown Data Width: Unknown Size: 13 GB Form Factor: Unknown Set: None Locator: M0003 Bank Locator: None Type: Unknown Type Detail: Unknown Speed: Unknown Manufacturer: Microsoft Corporation Serial Number: None Asset Tag: None Part Number: None Rank: Unknown Configured Memory Speed: Unknown Minimum Voltage: Unknown Maximum Voltage: Unknown Configured Voltage: Unknown Memory Technology: <OUT OF SPEC> Memory Operating Mode Capability: None Firmware Version: Not Specified Module Manufacturer ID: Unknown Module Product ID: Unknown Memory Subsystem Controller Manufacturer ID: Unknown Memory Subsystem Controller Product ID: Unknown Non-Volatile Size: None Volatile Size: None Cache Size: None Logical Size: None
Handle 0x000E, DMI type 19, 31 bytes Memory Array Mapped Address Starting Address: 0x00100000000 Ending Address: 0x004400003FF Range Size: 13 GB Physical Array Handle: 0x0006 Partition Width: 0
Handle 0x000F, DMI type 20, 35 bytes Memory Device Mapped Address Starting Address: 0x00100000000 Ending Address: 0x004400003FF Range Size: 13 GB Physical Device Handle: 0x000D Memory Array Mapped Address Handle: 0x000E Partition Row Position: Unknown
Handle 0x0010, DMI type 32, 11 bytes System Boot Information Status: No errors detected
Handle 0xFEFF, DMI type 127, 4 bytes End Of Table
The offending commit appers to be the backport of b15b7d2a1b09 ("uio_hv_generic: Let userspace take care of interrupt mask") for 6.12.y.
Peter confirmed that reverting this commit on top of 6.12.57-1 as packaged in Debian resolves indeed the issue. Interestingly the issue is *not* seen with 6.17.7 based kernel in Debian.
#regzbot introduced: 37bd91f22794dc05436130d6983302cb90ecfe7e #regzbot monitor: https://bugs.debian.org/1120602
Thank you already!
Regards, Salvatore