Kdump fails silently to capture a vmcore file when running kernel-rt on an EFI-boot system

Issue

• Kdump fails silently to capture a vmcore file when running kernel-rt on an EFI-boot system
  • Running sysrq-c to crash the kernel for testing:

[root@localhost ~]# echo c > /proc/sysrq-trigger 
    ...

• Then the kernel-rt just crashes and simply reboots without kdump kernel invocation:

localhost login: [  802.773525] sysrq: SysRq : Trigger a crash
[  802.773539] Kernel panic - not syncing:
[  802.773540] sysrq triggered crash
[  802.773540] CPU: 0 PID: 1878 Comm: bash Kdump: loaded Not tainted 4.18.0-553.16.1.rt7.357.el8_10.x86_64 #1
[  802.773545] Hardware name: VMware, Inc. VMware20,1/440BX Desktop Reference Platform, BIOS VMW201.00V.24504846.B64.2501180339 01/18/2025
[  802.773545] Call Trace:
[  802.773560]  dump_stack+0x41/0x60
[  802.773570]  panic+0xb9/0x2cd
[  802.773579]  ? printk+0x62/0x7d
[  802.773581]  sysrq_handle_crash+0x16/0x20
[  802.773588]  __handle_sysrq.cold.11+0x48/0x104
[  802.773589]  write_sysrq_trigger+0x2b/0x40
[  802.773590]  proc_reg_write+0x39/0x60
[  802.773597]  vfs_write+0xa5/0x1b0
[  802.773603]  ksys_write+0x52/0xc0
[  802.773604]  do_syscall_64+0x87/0x190
[  802.773608]  entry_SYSCALL_64_after_hwframe+0x66/0xcb
[  802.773614] RIP: 0033:0x7f96264a6a28
[  802.773616] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 15 4d 2a 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55
[  802.773617] RSP: 002b:00007ffcc68364e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  802.773619] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f96264a6a28
[  802.773619] RDX: 0000000000000002 RSI: 0000556ffe6e7d50 RDI: 0000000000000001
[  802.773620] RBP: 0000556ffe6e7d50 R08: 000000000000000a R09: 00007f9626506ae0
[  802.773620] R10: 000000000000000a R11: 0000000000000246 R12: 00007f96267476e0
[  802.773621] R13: 0000000000000002 R14: 00007f9626742860 R15: 0000000000000002

    ... The normal kernel-rt (not the kdump kernel) booting up from this point forward ...

[    0.000000] Linux version 4.18.0-553.16.1.rt7.357.el8_10.x86_64 (mockbuild@x86-64-04.build.eng.rdu2.redhat.com) (gcc version 8.5.0 20210514 (Red Hat 8.5.0-22) (GCC)) #1 SMP PREEMPT_RT Thu Aug 1 08:30:24 EDT 2024
[    0.000000] Command line: BOOT_IMAGE=(hd0,gpt2)/vmlinuz-4.18.0-553.16.1.rt7.357.el8_10.x86_64 root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap console=ttyS0,115200
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x200: 'Protection Keys User registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: xstate_offset[9]:  832, xstate_sizes[9]:    8
[    0.000000] x86/fpu: Enabled xstate features 0x207, context size is 840 bytes, using 'compacted' format.
    ...

• Secure boot is disabled on this EFI-boot system:

    ...
[    0.000000] efi: EFI v2.70 by VMware, Inc.
[    0.000000] efi:  SMBIOS=0xfbfb000  MEMATTR=0xf8c7018  ACPI 2.0=0xfbf1000  MOKvar=0xfbce000  RNG=0xfbcdf98
[    0.000000] efi: seeding entropy pool
[    0.000000] secureboot: Secure boot disabled
    ...

• kdumpctl shows that kdump service is operational:

# kdumpctl status
kdump: Kdump is operational

• systemctl shows that kdump.service is enabled and started successfully:

# systemctl status kdump.service
● kdump.service - Crash recovery kernel arming
   Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; vendor preset: enabled)
   Active: active (exited) since Thu 2025-07-31 07:34:27 EDT; 8h left
  Process: 1048 ExecStart=/usr/bin/kdumpctl start (code=exited, status=0/SUCCESS)
 Main PID: 1048 (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 23078)
   Memory: 0B
   CGroup: /system.slice/kdump.service

Jul 31 07:34:25 localhost.localdomain systemd[1]: Starting Crash recovery kernel arming...
Jul 31 07:34:27 localhost.localdomain kdumpctl[1066]: kdump: kexec: loaded kdump kernel
Jul 31 07:34:27 localhost.localdomain kdumpctl[1066]: kdump: Starting kdump: [OK]
Jul 31 07:34:27 localhost.localdomain systemd[1]: Started Crash recovery kernel arming.

• KEXEC_ARGS="-s" is set to enforce the use of kexec_file_load syscall

[root@localhost ~]# cat /etc/sysconfig/kdump | grep ^KEXEC_ARGS
KEXEC_ARGS="-s"