CPU is AMD Ryzen 9 5950X 16-Core Processor (32 threads)

GPU is an Rx580
0d:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] (rev e7)

I have discovered this happens when there are two monitors plugged into my displayport switch.  If I run monitor 4 on hdmi directly, the crash stops happening.

(In reply to Gerhard Mack from comment #0)
> If I attempt to change my screen layout in XFCE, I get a kernel NULL pointer
> crash.  This is very reproduceable.
> 
> [   50.275982] BUG: kernel NULL pointer dereference, address:
> 0000000000000008
> [   50.275988] #PF: supervisor read access in kernel mode
> [   50.275989] #PF: error_code(0x0000) - not-present page
> [   50.275991] PGD 0 P4D 0 
> [   50.275993] Oops: 0000 [#1] PREEMPT SMP NOPTI
> [   50.275995] CPU: 18 PID: 1931 Comm: Xorg Not tainted 6.6.1 #106
> d284c8807aa68b715e3e2f475c4079807a0b5cb5
> [   50.275997] Hardware name: To Be Filled By O.E.M. B550 Taichi/B550
> Taichi, BIOS P3.20 09/27/2023
> [   50.275999] RIP: 0010:drm_dp_atomic_find_time_slots+0x57/0x1e0
> [drm_display_helper]
> [   50.276007] Code: 0f 87 9d 01 00 00 48 8b 85 28 05 00 00 31 d2 48 63 80
> 88 00 00 00 41 3b 44 24 28 7d 0d 48 6b c0 28 49 03 44 24 30 48 8b 50 18 <48>
> 8b 42 08 48 89 ee 48 89 df 8b 88 90 00 00 00 b8 01 00 00 00 d3
> [   50.276008] RSP: 0018:ffffad10544b76d8 EFLAGS: 00010286
> [   50.276010] RAX: ffff9409ea510ca0 RBX: ffff940994c46900 RCX:
> 0000000000000002
> [   50.276011] RDX: 0000000000000000 RSI: ffff940996bd0578 RDI:
> ffff9409b11b7b00
> [   50.276012] RBP: ffff94099317b800 R08: ffffad10544b7a58 R09:
> 0000000000000001
> [   50.276012] R10: 0000000000000000 R11: 0000000000000000 R12:
> ffff9409b11b7b00
> [   50.276013] R13: ffff940996bd0578 R14: 0000000000000224 R15:
> 0000000094c46900
> [   50.276014] FS:  00007f4296208ac0(0000) GS:ffff94187ee80000(0000)
> knlGS:0000000000000000
> [   50.276015] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   50.276016] CR2: 0000000000000008 CR3: 000000010612e000 CR4:
> 0000000000f50ee0
> [   50.276017] PKRU: 55555554
> [   50.276018] Call Trace:
> [   50.276020]  <TASK>
> [   50.276021]  ? __die_body+0x15/0x54
> [   50.276026]  ? page_fault_oops+0x323/0x36d
> [   50.276030]  ? post_alloc_hook+0x9/0x50
> [   50.276033]  ? prep_new_page+0x2c/0x41
> [   50.276035]  ? get_page_from_freelist+0x6c4/0x7f6
> [   50.276036]  ? exc_page_fault+0x159/0x4f9
> [   50.276039]  ? asm_exc_page_fault+0x26/0x30
> [   50.276043]  ? drm_dp_atomic_find_time_slots+0x57/0x1e0
> [drm_display_helper 13cd3e40727f81da5f41f67251f92c3e185bfce2]
> [   50.276047]  ? drm_dp_atomic_find_time_slots+0x21/0x1e0
> [drm_display_helper 13cd3e40727f81da5f41f67251f92c3e185bfce2]
> [   50.276051]  compute_mst_dsc_configs_for_link+0x29b/0x7fd [amdgpu
> 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276121]  ? free_tail_page_prepare+0xc0/0xdb
> [   50.276123]  ? free_unref_page_commit+0x29/0xeb
> [   50.276127]  compute_mst_dsc_configs_for_state+0x119/0x1a8 [amdgpu
> 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276178]  amdgpu_dm_atomic_check+0x9ba/0xd9e [amdgpu
> 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276229]  ? kmem_cache_debug_flags+0x5/0x11
> [   50.276232]  ? amdgpu_dm_connector_atomic_duplicate_state+0x24/0xa4
> [amdgpu 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276280]  ? kmem_cache_debug_flags+0x5/0x11
> [   50.276281]  ? slab_post_alloc_hook+0x70/0x17f
> [   50.276284]  ? slab_pre_alloc_hook.constprop.0+0x49/0x14c
> [   50.276286]  ? amdgpu_dm_connector_atomic_duplicate_state+0x24/0xa4
> [amdgpu 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276344]  ? __kmem_cache_alloc_node+0x10b/0x137
> [   50.276345]  drm_atomic_check_only+0x6df/0x812
> [   50.276349]  ? __drm_connector_put_safe+0x11/0x49
> [   50.276351]  drm_atomic_commit+0x6a/0xc1
> [   50.276352]  ? __drm_printfn_seq_file+0x17/0x17
> [   50.276355]  ? __drm_printfn_seq_file+0x17/0x17
> [   50.276356]  drm_atomic_connector_commit_dpms+0xc1/0xda
> [   50.276358]  drm_mode_obj_set_property_ioctl+0xff/0x293
> [   50.276361]  ? drm_connector_set_obj_prop+0x63/0x63
> [   50.276362]  drm_connector_property_set_ioctl+0x36/0x51
> [   50.276364]  drm_ioctl_kernel+0xe9/0x13c
> [   50.276366]  drm_ioctl+0x278/0x3a4
> [   50.276368]  ? drm_connector_set_obj_prop+0x63/0x63
> [   50.276369]  ? rpm_resume+0x8b/0x3eb
> [   50.276372]  amdgpu_drm_ioctl+0x4a/0x79 [amdgpu
> 98fd76f1aa24e802b0010b76204b9775aacb3c0c]
> [   50.276414]  vfs_ioctl+0x1d/0x2b
> [   50.276418]  __do_sys_ioctl+0x67/0x8a
> [   50.276420]  do_syscall_64+0x82/0xa3
> [   50.276422]  ? syscall_exit_to_user_mode+0x34/0x37
> [   50.276424]  ? do_syscall_64+0x9c/0xa3
> [   50.276425]  ? vfs_ioctl+0x1d/0x2b
> [   50.276426]  ? __do_sys_ioctl+0x78/0x8a
> [   50.276428]  ? exit_to_user_mode_prepare+0x15/0x108
> [   50.276430]  ? syscall_exit_to_user_mode+0x34/0x37
> [   50.276432]  ? do_syscall_64+0x9c/0xa3
> [   50.276433]  ? syscall_exit_to_user_mode+0x34/0x37
> [   50.276435]  ? do_syscall_64+0x9c/0xa3
> [   50.276436]  ? do_syscall_64+0x9c/0xa3
> [   50.276437]  ? do_syscall_64+0x9c/0xa3
> [   50.276438]  ? do_syscall_64+0x9c/0xa3
> [   50.276440]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [   50.276442] RIP: 0033:0x7f4295f1b51b
> [   50.276444] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00
> 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89>
> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
> [   50.276445] RSP: 002b:00007ffc95c20100 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
> [   50.276446] RAX: ffffffffffffffda RBX: 00005609596da8c0 RCX:
> 00007f4295f1b51b
> [   50.276447] RDX: 00007ffc95c20190 RSI: 00000000c01064ab RDI:
> 000000000000000f
> [   50.276448] RBP: 00007ffc95c20190 R08: 0000000000000000 R09:
> 00005609596dafe0
> [   50.276449] R10: 0000000000000000 R11: 0000000000000246 R12:
> 00000000c01064ab
> [   50.276449] R13: 000000000000000f R14: 00005609596d9340 R15:
> 0000000000000000
> [   50.276451]  </TASK>
> [   50.276451] Modules linked in: rfcomm snd_seq_dummy snd_hrtimer tun
> l2tp_ppp l2tp_netlink l2tp_core xfrm_interface xfrm6_tunnel pppox tunnel6
> tunnel4 ppp_generic slhc xfrm_user xfrm_algo algif_hash algif_skcipher
> af_alg binfmt_misc nls_utf8 nls_cp437 vfat fat squashfs crc32_pclmul
> polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 uvcvideo
> aesni_intel wmi_bmof crypto_simd videobuf2_vmalloc cryptd uvc btusb
> videobuf2_memops btrtl pcspkr videobuf2_v4l2 btintel snd_usb_audio
> videobuf2_common btbcm ccp btmtk snd_usbmidi_lib joydev snd_ump snd_rawmidi
> tpm_tis tpm_tis_core sg evdev bonding tls lm92 msr loop efi_pstore dm_mod
> tpm rng_core ip_tables x_tables autofs4 sd_mod raid10 raid456
> async_raid6_recov async_memcpy async_pq async_xor async_tx raid1 raid0
> multipath linear md_mod amdgpu amdxcp drm_exec mfd_core gpu_sched drm_buddy
> video drm_suballoc_helper i2c_algo_bit crc32c_intel drm_ttm_helper
> hid_generic ttm atlantic usb_storage drm_display_helper sr_mod cdrom wmi
> [   50.276492] CR2: 0000000000000008
> [   50.276494] ---[ end trace 0000000000000000 ]---
> [   50.276494] RIP: 0010:drm_dp_atomic_find_time_slots+0x57/0x1e0
> [drm_display_helper]
> [   50.276499] Code: 0f 87 9d 01 00 00 48 8b 85 28 05 00 00 31 d2 48 63 80
> 88 00 00 00 41 3b 44 24 28 7d 0d 48 6b c0 28 49 03 44 24 30 48 8b 50 18 <48>
> 8b 42 08 48 89 ee 48 89 df 8b 88 90 00 00 00 b8 01 00 00 00 d3
> [   50.276500] RSP: 0018:ffffad10544b76d8 EFLAGS: 00010286
> [   50.276501] RAX: ffff9409ea510ca0 RBX: ffff940994c46900 RCX:
> 0000000000000002
> [   50.276502] RDX: 0000000000000000 RSI: ffff940996bd0578 RDI:
> ffff9409b11b7b00
> [   50.276503] RBP: ffff94099317b800 R08: ffffad10544b7a58 R09:
> 0000000000000001
> [   50.276503] R10: 0000000000000000 R11: 0000000000000000 R12:
> ffff9409b11b7b00
> [   50.276504] R13: ffff940996bd0578 R14: 0000000000000224 R15:
> 0000000094c46900
> [   50.276505] FS:  00007f4296208ac0(0000) GS:ffff94187ee80000(0000)
> knlGS:0000000000000000
> [   50.276506] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   50.276507] CR2: 0000000000000008 CR3: 000000010612e000 CR4:
> 0000000000f50ee0
> [   50.276508] PKRU: 55555554
> [   50.276508] note: Xorg[1931] exited with irqs disabled

Please also open an issue on freedesktop tracker [1].

[1]: https://gitlab.freedesktop.org/drm/amd/-/issues

I have opened the bug report as requested (https://gitlab.freedesktop.org/drm/amd/-/issues/2981)

I also found this while I was digging in the logs and it was just prior to the crash:

[ T8277] [drm] enabling link 2 failed: 15
[T735019] [drm] DM_MST: starting TM on aconnector: 00000000c46ac3ce [id: 90]
[T735019] [drm] DM_MST: DP14, 4-lane link detected
[ T1964] [drm] Downstream port present 1, type 0
[ T1964] [drm] Downstream port present 1, type 0