The kdump kernel panics when we try to test kdump with sysrq on Windows Server 2022 Hyper-V guest.

Issue

• The kdump kernel panics when we try to test kdump with sysrq on Windows Server 2022 Hyper-V guest by 'echo c > /proc/sysrq-trigger' or by sysrq keyboard shortcut.

[    8.123089] BUG: unable to handle kernel NULL pointer dereference at 0000000000000070
[    8.129095] PGD 0 P4D 0
[    8.131449] Oops: 0000 [#1] SMP NOPTI
[    8.136325] CPU: 0 PID: 446 Comm: udevadm Not tainted 4.18.0-425.3.1.el8.x86_64 #1
[    8.142533] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008  12/07/2018
[    8.149130] RIP: 0010:relid2channel+0x1a/0x30 [hv_vmbus]
[    8.153109] Code: 00 00 e8 19 b3 f8 c0 e9 78 ff ff ff 0f 1f 40 00 0f 1f 44 00 00 81 ff ff 07 00 00 77 15 48 8b 05 5c 08 01 00 89 ff 48 8d 04 f8 <48> 8b 00 e9 4e bd b0 c1 0f 0b 31 c0 e9 45 bd b0 c1 0f 1f 44 00 00
[    8.167410] RSP: 0000:ffffc90000003fa0 EFLAGS: 00010097
[    8.173429] RAX: 0000000000000070 RBX: 0000000000000000 RCX: 000000000000000e
[    8.178581] RDX: 000000000000000e RSI: 0000000000000800 RDI: 000000000000000e
[    8.183719] RBP: ffff888071928200 R08: 0000000000000002 R09: 011d78fdf85920cc
[    8.188700] R10: 0000000000000000 R11: 0000000000000000 R12: ffffe8ffffc02140
[    8.193556] R13: 000000000000000e R14: 0000000000000000 R15: 0000000000000000
[    8.198736] FS:  00007f77504c2280(0000) GS:ffff888075600000(0000) knlGS:0000000000000000
[    8.204524] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    8.208836] CR2: 0000000000000070 CR3: 000000007185e000 CR4: 0000000000350eb0
[    8.214004] Call Trace:
[    8.216305]  <IRQ>
[    8.218551]  vmbus_isr+0x6c/0x230 [hv_vmbus]
[    8.224015]  ? sched_clock_cpu+0xc/0xb0
[    8.229077]  hyperv_vector_handler+0x3b/0x70
[    8.233409]  hyperv_callback_vector+0xf/0x20
[    8.236811]  </IRQ>
[    8.238856] RIP: 0010:copy_page+0x7/0x10
[    8.242007] Code: 75 11 65 48 89 1e 65 48 89 4e 08 9d b0 01 e9 f0 6e 22 00 9d 30 c0 e9 e8 6e 22 00 90 90 90 90 90 90 90 90 66 90 b9 00 02 00 00 <f3> 48 a5 e9 d1 6e 22 00 90 48 83 ec 10 48 89 1c 24 4c 89 64 24 08
[    8.253955] RSP: 0000:ffffc900006b7d08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff0c
[    8.259155] RAX: ffffea0001c45580 RBX: ffff88806da32800 RCX: 00000000000001dc
[    8.264302] RDX: 00000000006200ca RSI: ffff8880738f1120 RDI: ffff888071156120
[    8.269611] RBP: ffff88807185c0e8 R08: 0000000000000000 R09: 0000000000001f09
[    8.274781] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888071fba400
[    8.280033] R13: ffffea0001ce3c40 R14: ffffea0001c45580 R15: 0000000000000255
[    8.284885]  copy_user_highpage.isra.81+0x49/0x60
[    8.288420]  __wp_page_copy+0x9c/0x540
[    8.291698]  do_wp_page+0xed/0x350
[    8.296273]  __handle_mm_fault+0x453/0x6c0
[    8.300192]  handle_mm_fault+0xc1/0x1e0
[    8.303304]  do_user_addr_fault+0x1b9/0x450
[    8.306644]  do_page_fault+0x37/0x130
[    8.309688]  ? page_fault+0x8/0x30
[    8.312610]  page_fault+0x1e/0x30
[    8.315398] RIP: 0033:0x7f77502b8258
[    8.318215] Code: 00 00 49 8b 14 24 41 8b 44 24 08 4c 01 fa 48 83 f8 26 74 0a 48 83 f8 08 0f 85 2b 14 00 00 49 8b 44 24 10 49 83 c4 18 4c 01 f8 <48> 89 02 4c 39 e3 77 d0 4d 8b 9a d0 01 00 00 4d 85 db 0f 85 a2 f9
[    8.332906] RSP: 002b:00007fff7bd50f10 EFLAGS: 00010206
[    8.336804] RAX: 00007f774bd116c3 RBX: 00007f774bcbc518 RCX: 00007f77504d3a30
[    8.341844] RDX: 00007f774c02c008 RSI: 00007f774bcb0710 RDI: 00007f774bcbf5c0
[    8.346762] RBP: 00007fff7bd51020 R08: 00007f774bcbf5c0 R09: 0000000000006960
[    8.351569] R10: 00007f77504c8080 R11: 0000000000000206 R12: 00007f774bcb91b8
[    8.356788] R13: 0000000000000000 R14: 0000000000000012 R15: 00007f774bcaf000
[    8.361955] Modules linked in: hv_vmbus(+) dm_mirror dm_region_hash dm_log dm_mod fuse overlay squashfs loop
[    8.368704] CR2: 0000000000000070
[    8.371482] ---[ end trace c8ef4549dc3a5e3a ]---
[    8.377016] RIP: 0010:relid2channel+0x1a/0x30 [hv_vmbus]
[    8.381243] Code: 00 00 e8 19 b3 f8 c0 e9 78 ff ff ff 0f 1f 40 00 0f 1f 44 00 00 81 ff ff 07 00 00 77 15 48 8b 05 5c 08 01 00 89 ff 48 8d 04 f8 <48> 8b 00 e9 4e bd b0 c1 0f 0b 31 c0 e9 45 bd b0 c1 0f 1f 44 00 00
[    8.393392] RSP: 0000:ffffc90000003fa0 EFLAGS: 00010097
[    8.397385] RAX: 0000000000000070 RBX: 0000000000000000 RCX: 000000000000000e
[    8.402494] RDX: 000000000000000e RSI: 0000000000000800 RDI: 000000000000000e
[    8.407663] RBP: ffff888071928200 R08: 0000000000000002 R09: 011d78fdf85920cc
[    8.412503] R10: 0000000000000000 R11: 0000000000000000 R12: ffffe8ffffc02140
[    8.418921] R13: 000000000000000e R14: 0000000000000000 R15: 0000000000000000
[    8.425443] FS:  00007f77504c2280(0000) GS:ffff888075600000(0000) knlGS:0000000000000000
[    8.432207] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    8.439055] CR2: 0000000000000070 CR3: 000000007185e000 CR4: 0000000000350eb0
[    8.445299] Kernel panic - not syncing: Fatal exception in interrupt
[    8.449927] Kernel Offset: disabled
[    8.452827] Rebooting in 10 seconds..