The bug is in lib/test_kho.c, when KHO is not enabled, it should not run KHO commands, there is a function to test that: kho_is_enabled(). So, KHO is disabled and kho_add_subtree() which calles add debugfs entry, and the list is not initialized, because KHO is disabled. The fix is:

diff --git a/lib/test_kho.c b/lib/test_kho.c index 025ea251a186..85b60d87a50a 100644 --- a/lib/test_kho.c +++ b/lib/test_kho.c @@ -315,6 +315,9 @@ static int __init kho_test_init(void) phys_addr_t fdt_phys; int err;

+ if (!kho_is_enabled()) + return 0; + err = kho_retrieve_subtree(KHO_TEST_FDT, &fdt_phys); if (!err) return kho_test_restore(fdt_phys);

On Thu, Nov 6, 2025 at 3:41 AM kernel test robot oliver.sang@intel.com wrote:

Hello,

kernel test robot noticed "WARNING:at_kernel/kexec_handover.c:#kho_add_subtree" on:

commit: e44a700c561d1e892a8d0829d557e221604a7b93 ("[PATCH v9 2/9] kho: drop notifiers") url: https://github.com/intel-lab-lkp/linux/commits/Pasha-Tatashin/kho-make-debug... patch link: https://lore.kernel.org/all/20251101142325.1326536-3-pasha.tatashin@soleen.c... patch subject: [PATCH v9 2/9] kho: drop notifiers

in testcase: boot

config: x86_64-randconfig-001-20251015 compiler: gcc-14 test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

(please refer to attached dmesg/kmsg for entire log/backtrace)

+--------------------------------------------------------+------------+------------+ | | 93e4b3b2e9 | e44a700c56 | +--------------------------------------------------------+------------+------------+ | WARNING:at_kernel/kexec_handover.c:#kho_add_subtree | 0 | 8 | | RIP:kho_add_subtree | 0 | 8 | +--------------------------------------------------------+------------+------------+

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot oliver.sang@intel.com | Closes: https://lore.kernel.org/oe-lkp/202511061629.e242724-lkp@intel.com

[ 13.620111][ T1] ------------[ cut here ]------------ [ 13.620739][ T1] WARNING: CPU: 1 PID: 1 at kernel/kexec_handover.c:704 kho_add_subtree (kernel/kexec_handover.c:704) [ 13.621665][ T1] Modules linked in: [ 13.622090][ T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.0-rc3-00211-ge44a700c561d #1 VOLUNTARY [ 13.623073][ T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 13.624054][ T1] RIP: 0010:kho_add_subtree (kernel/kexec_handover.c:704) [ 13.624596][ T1] Code: c7 38 b4 ac 85 31 ed e8 01 1c 00 00 48 c7 c7 70 5a ca 86 85 c0 89 c3 40 0f 95 c5 31 c9 31 d2 89 ee e8 37 b5 0a 00 85 db 74 02 <0f> 0b b9 01 00 00 00 31 d2 89 ee 48 c7 c7 40 5a ca 86 e8 1c b5 0a All code ======== 0: c7 38 b4 ac 85 xbegin 0xffffffff85acb43d,(bad) 5: 31 ed xor %ebp,%ebp 7: e8 01 1c 00 00 call 0x1c0d c: 48 c7 c7 70 5a ca 86 mov $0xffffffff86ca5a70,%rdi 13: 85 c0 test %eax,%eax 15: 89 c3 mov %eax,%ebx 17: 40 0f 95 c5 setne %bpl 1b: 31 c9 xor %ecx,%ecx 1d: 31 d2 xor %edx,%edx 1f: 89 ee mov %ebp,%esi 21: e8 37 b5 0a 00 call 0xab55d 26: 85 db test %ebx,%ebx 28: 74 02 je 0x2c 2a:* 0f 0b ud2 <-- trapping instruction 2c: b9 01 00 00 00 mov $0x1,%ecx 31: 31 d2 xor %edx,%edx 33: 89 ee mov %ebp,%esi 35: 48 c7 c7 40 5a ca 86 mov $0xffffffff86ca5a40,%rdi 3c: e8 .byte 0xe8 3d: 1c b5 sbb $0xb5,%al 3f: 0a .byte 0xa

Code starting with the faulting instruction

0: 0f 0b ud2 2: b9 01 00 00 00 mov $0x1,%ecx 7: 31 d2 xor %edx,%edx 9: 89 ee mov %ebp,%esi b: 48 c7 c7 40 5a ca 86 mov $0xffffffff86ca5a40,%rdi 12: e8 .byte 0xe8 13: 1c b5 sbb $0xb5,%al 15: 0a .byte 0xa [ 13.626370][ T1] RSP: 0018:ffffc9000001fca0 EFLAGS: 00010286 [ 13.626951][ T1] RAX: dffffc0000000000 RBX: 00000000ffffffff RCX: 0000000000000000 [ 13.627737][ T1] RDX: 1ffffffff0d94b52 RSI: 0000000000000001 RDI: ffffffff86ca5a90 [ 13.628523][ T1] RBP: 0000000000000001 R08: 0000000000000008 R09: fffffbfff0dfac4c [ 13.629330][ T1] R10: 0000000000000000 R11: ffffffff86fd6267 R12: ffff888133ee2000 [ 13.630101][ T1] R13: ffffffff85acb340 R14: ffff888117a5f988 R15: dffffc0000000000 [ 13.630869][ T1] FS: 0000000000000000(0000) GS:ffff888426ea0000(0000) knlGS:0000000000000000 [ 13.631727][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 13.632370][ T1] CR2: 00007f586df260ac CR3: 00000000054ea000 CR4: 00000000000406f0 [ 13.633154][ T1] Call Trace: [ 13.633506][ T1] <TASK> [ 13.633833][ T1] kho_test_prepare_fdt+0x145/0x180 [ 13.634446][ T1] ? kho_test_save_data+0x210/0x210 [ 13.635097][ T1] ? csum_partial (lib/checksum.c:123) [ 13.635546][ T1] kho_test_init (lib/test_kho.c:177 lib/test_kho.c:284) [ 13.636018][ T1] ? vmalloc_test_init (lib/test_kho.c:271) [ 13.636508][ T1] ? add_device_randomness (drivers/char/random.c:944) [ 13.637485][ T1] ? mix_pool_bytes (drivers/char/random.c:944) [ 13.637955][ T1] ? trace_initcall_start (include/trace/events/initcall.h:27 (discriminator 3)) [ 13.638498][ T1] ? vmalloc_test_init (lib/test_kho.c:271) [ 13.638989][ T1] do_one_initcall (init/main.c:1284) [ 13.639477][ T1] ? trace_initcall_start (init/main.c:1274) [ 13.639998][ T1] ? parse_one (kernel/params.c:143) [ 13.640455][ T1] ? kasan_save_track (mm/kasan/common.c:69 (discriminator 1) mm/kasan/common.c:78 (discriminator 1)) [ 13.640948][ T1] ? __kmalloc_noprof (mm/slub.c:5659) [ 13.641465][ T1] do_initcalls (init/main.c:1344 (discriminator 3) init/main.c:1361 (discriminator 3)) [ 13.641924][ T1] kernel_init_freeable (init/main.c:1595) [ 13.642441][ T1] ? rest_init (init/main.c:1475) [ 13.642891][ T1] kernel_init (init/main.c:1485) [ 13.643345][ T1] ? rest_init (init/main.c:1475) [ 13.643788][ T1] ret_from_fork (arch/x86/kernel/process.c:164) [ 13.644256][ T1] ? rest_init (init/main.c:1475) [ 13.644703][ T1] ret_from_fork_asm (arch/x86/entry/entry_64.S:255) [ 13.645213][ T1] </TASK> [ 13.645540][ T1] irq event stamp: 132025 [ 13.645971][ T1] hardirqs last enabled at (132035): __up_console_sem (arch/x86/include/asm/irqflags.h:26 arch/x86/include/asm/irqflags.h:109 arch/x86/include/asm/irqflags.h:151 kernel/printk/printk.c:345) [ 13.646887][ T1] hardirqs last disabled at (132046): __up_console_sem (kernel/printk/printk.c:343 (discriminator 3)) [ 13.648253][ T1] softirqs last enabled at (131286): handle_softirqs (kernel/softirq.c:469 (discriminator 1) kernel/softirq.c:650 (discriminator 1)) [ 13.649690][ T1] softirqs last disabled at (131281): __irq_exit_rcu (kernel/softirq.c:496 kernel/softirq.c:723) [ 13.651128][ T1] ---[ end trace 0000000000000000 ]---

The kernel config and materials to reproduce are available at: https://download.01.org/0day-ci/archive/20251106/202511061629.e242724-lkp@in...

-- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki