PROBLEM: CPU hotplug leads to NULL pointer dereference with RAPL enabled on AMD 2990WX

[Johnathan Smithinovic]

CPU hotplug leads to NULL pointer dereference with RAPL enabled on AMD 2990WX


When hot-plugging CPUs (e.g. manually or on suspend) I get a NULL
pointer dereference in rapl_cpu_offline() for CPUs 16 and 24.
It *seems* to me that this has to do with commit
700d098acec5271161606f3c0086b71695ea2ef8
("x86/CPU/AMD: Save AMD NodeId as cpu_die_id").
When reverting said commit hotplug works again.


I have been able to reproduce this on 5.10.4 and 5.11-rc1; 5.4.86 appears
to be not affected because RAPL does not seem to get enabled for the CPU
in use.
(CPUs 16 and 24 are not siblings according to
/sys/devices/system/cpu/cpu16/topology/thread_siblings_list in case that is
relevant.)


Steps to reproduce (on my system (ubuntu 18.04), as root):
	echo 0 > /sys/devices/system/cpu/cpu16/hotplug/target
(When turning off RAPL by unsetting "PERF_EVENTS_INTEL_RAPL" I seem to be able
to hot-plug the mentioned CPUs without reverting 700d098acec5.)

(In order to be able to test this with 5.11-rc1 on my system I had to revert
commit f36a74b9345aebaf5d325380df87a54720229d18.)


Relevant part of dmesg when trying to turn off CPU16:

[   46.828426] BUG: kernel NULL pointer dereference, address: 0000000000000008
[   46.828467] #PF: supervisor write access in kernel mode
[   46.828493] #PF: error_code(0x0002) - not-present page
[   46.828518] PGD 0 P4D 0
[   46.828534] Oops: 0002 [#1] SMP NOPTI
[   46.828554] CPU: 16 PID: 107 Comm: cpuhp/16 Not tainted 5.11.0-rc1-bisect #1
[   46.828589] Hardware name: System manufacturer System Product Name/ROG ZENITH
EXTREME, BIOS 1701 01/09/2019
[   46.828632] RIP: 0010:rapl_cpu_offline+0x51/0xb0 [rapl]
[   46.828663] Code: 0d 84 2c 00 00 45 31 e4 3b 91 28 01 00 00 73 08 4c 8b a4 d1
30 01 00 00 f0 48 0f b3 05 68 28 00 00 72 07 5b 31 c0 41 5c 5d c3 <41> c7 44 24
08 ff ff ff ff 48 8b 04 c5 00 89 28 9d 89 fb 48 c7 c2
[   46.828746] RSP: 0018:ffffaaba8397be48 EFLAGS: 00010247
[   46.828773] RAX: 0000000000000010 RBX: ffff9963ee018760 RCX: ffff9960108cbc00
[   46.828807] RDX: 0000000000000002 RSI: 000000000000009e RDI: 0000000000000010
[   46.828839] RBP: ffffaaba8397be58 R08: ffff9963ee018788 R09: 0000000000000000
[   46.828872] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[   46.828905] R13: 0000000000000010 R14: ffff9963ee018788 R15: ffff9960020ec8c0
[   46.828938] FS:  0000000000000000(0000) GS:ffff9963ee000000(0000)
knlGS:0000000000000000
[   46.828975] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   46.829003] CR2: 0000000000000008 CR3: 000000076b810000 CR4: 00000000003506e0
[   46.829036] Call Trace:
[   46.829052]  ? rapl_hrtimer_handle+0xa0/0xa0 [rapl]
[   46.829078]  cpuhp_invoke_callback+0x85/0x410
[   46.829105]  ? sort_range+0x30/0x30
[   46.829125]  cpuhp_thread_fun+0xb8/0x120
[   46.829145]  smpboot_thread_fn+0xfc/0x170
[   46.829166]  kthread+0x126/0x140
[   46.829185]  ? kthread_park+0x90/0x90
[   46.829206]  ret_from_fork+0x22/0x30
[   46.829229] Modules linked in: xt_CHECKSUM iptable_mangle xt_MASQUERADE
bridge stp llc iptable_filter xt_nat xt_tcpudp iptable_nat nf_nat nf_conntrack
nf_defrag_ipv6 nf_defrag_ipv4 bpfilter binfmt_misc snd_hda_codec_realtek
snd_hda_codec_generic ledtrig_audio snd_hda_codec_hdmi snd_hda_intel
snd_intel_dspcfg nls_iso8859_1 soundwire_intel soundwire_generic_allocation
soundwire_cadence joydev input_leds snd_hda_codec snd_hda_core snd_hwdep
intel_rapl_msr soundwire_bus intel_rapl_common snd_soc_core snd_compress
amd64_edac_mod ac97_bus snd_pcm_dmaengine edac_mce_amd snd_pcm kvm_amd
snd_seq_midi kvm snd_seq_midi_event rapl snd_rawmidi eeepc_wmi asus_wmi
sparse_keymap snd_seq video wmi_bmof snd_seq_device snd_timer snd efi_pstore
soundcore k10temp ccp mac_hid sch_fq_codel ib_iser rdma_cm iw_cm ib_cm ib_core
iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi parport_pc ppdev lp parport
ip_tables x_tables autofs4 btrfs blake2b_generic raid10 raid456
async_raid6_recov async_memcpy async_pq
[   46.829309]  async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath
linear hid_cherry hid_generic usbhid hid mxm_wmi crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper nvme igb
nvme_core dca ahci i2c_piix4 xhci_pci i2c_algo_bit libahci xhci_pci_renesas
gpio_amdpt wmi gpio_generic
[   46.829830] CR2: 0000000000000008
[   46.829848] ---[ end trace 5c9c68d47cf771f6 ]---
[   46.881781] RIP: 0010:rapl_cpu_offline+0x51/0xb0 [rapl]
[   46.881808] Code: 0d 84 2c 00 00 45 31 e4 3b 91 28 01 00 00 73 08 4c 8b a4 d1
30 01 00 00 f0 48 0f b3 05 68 28 00 00 72 07 5b 31 c0 41 5c 5d c3 <41> c7 44 24
08 ff ff ff ff 48 8b 04 c5 00 89 28 9d 89 fb 48 c7 c2
[   46.881885] RSP: 0018:ffffaaba8397be48 EFLAGS: 00010247
[   46.882413] RAX: 0000000000000010 RBX: ffff9963ee018760 RCX: ffff9960108cbc00
[   46.886575] RDX: 0000000000000002 RSI: 000000000000009e RDI: 0000000000000010
[   46.891210] RBP: ffffaaba8397be58 R08: ffff9963ee018788 R09: 0000000000000000
[   46.895849] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[   46.900579] R13: 0000000000000010 R14: ffff9963ee018788 R15: ffff9960020ec8c0
[   46.904623] FS:  0000000000000000(0000) GS:ffff9963ee000000(0000)
knlGS:0000000000000000
[   46.909198] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   46.913625] CR2: 0000000000000008 CR3: 00000004adf54000 CR4: 00000000003506e0




Kind regards
John