B580 on POWER9: Unable to handle kernel data access on read at 0xc00a0000000003cc

[Simon Richter <Simon.Richter@xxxxxxxxxx>]

Hi,

I've built a horrible contraption and received the following output:

BUG: Unable to handle kernel data access on read at 0xc00a0000000003cc
Faulting instruction address: 0xc00800000dd46484
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=4K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in: xe(+) xt_conntrack nft_chain_nat xt_MASQUERADE nf_nat 
nf_conntrack_netlink nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 
xfrm_user xfrm_algo xt_addrtype nft_compat x_tables nf_tables libcrc32c 
nfnetlink br_netfilter bridge stp llc overlay binfmt_misc evdev joydev 
hid_generic usbhid hid cec rc_core drm_gpuvm drm_exec drm_buddy 
gpu_sched drm_suballoc_helper drm_display_helper ast drm_ttm_helper ttm 
snd_hda_intel drm_shmem_helper snd_intel_dspcfg drm_kms_helper 
snd_hda_codec snd_hda_core drm ofpart snd_hwdep snd_pcm xts ipmi_powernv 
snd_timer ipmi_devintf powernv_flash snd vmx_crypto gf128mul mtd 
ipmi_msghandler opal_prd soundcore at24 drm_panel_orientation_quirks 
i2c_algo_bit regmap_i2c ext4 crc16 mbcache jbd2 crc32c_generic dm_mod 
xhci_pci xhci_hcd tg3 nvme crc32c_vpmsum usbcore nvme_core libphy 
usb_common nvme_auth [last unloaded: xe]
CPU: 32 UID: 0 PID: 453 Comm: kworker/32:1 Not tainted 
6.12.12+bpo-powerpc64le #1  Debian 6.12.12-1~bpo12+1
Hardware name: T2P9D01 REV 1.01 POWER9 0x4e1202 opal:skiboot-9858186 PowerNV
Workqueue: events work_for_cpu_fn
NIP:  c00800000dd46484 LR: c00800000dd46384 CTR: 000000003006c394
REGS: c00020000a637660 TRAP: 0300   Not tainted 
(6.12.12+bpo-powerpc64le Debian 6.12.12-1~bpo12+1)
MSR:  9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>  CR: 24008488  XER: 
20040000
CFAR: c00800000dd46398 DAR: c00a0000000003cc DSISR: 40000000 IRQMASK: 0
GPR00: c00800000dd46384 c00020000a637900 c00800000db30600 c00a0000000003cc
GPR04: 0000000000000000 0000000000000004 0000000035c20060 0000000035c20060
GPR08: 0000000000000000 c00a000000000000 0000000000000000 0000000000008000
GPR12: 0000000000000000 c0002007ff7ffb00 c00000000017d1cc c000200005d5c200
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 c0002007fbeeb280 c00800000df35350 c00800000df35700
GPR24: c00800000df35730 c000200006f60000 0000000000000001 c000200006f61628
GPR28: 0000000000000001 c0000000027703e0 0000000000000000 c00000000c167000
NIP [c00800000dd46484] intel_vga_reset_io_mem+0x140/0x188 [xe]
LR [c00800000dd46384] intel_vga_reset_io_mem+0x40/0x188 [xe]
Call Trace:
[c00020000a637900] [c00800000dd46384] intel_vga_reset_io_mem+0x40/0x188 
[xe] (unreliable)
[c00020000a637940] [c00800000dcbbd88] hsw_power_well_enable+0x1f0/0x238 [xe]
[c00020000a637990] [c00800000dcbe470] intel_power_well_enable+0x8c/0xb8 [xe]
[c00020000a637a00] [c00800000dcb6d08] 
__intel_display_power_get_domain.part.0+0x98/0xf4 [xe]
[c00020000a637a50] [c00800000dcb9260] 
intel_power_domains_init_hw+0x94/0x3a8 [xe]
[c00020000a637af0] [c00800000dcafca4] 
intel_display_driver_probe_noirq+0xf4/0x300 [xe]
[c00020000a637b70] [c00800000dc4f124] xe_display_init_noirq+0x80/0x124 [xe]
[c00020000a637ba0] [c00800000dbcee98] xe_device_probe+0x414/0x768 [xe]
[c00020000a637c30] [c00800000dc13370] xe_pci_probe+0x77c/0xc60 [xe]
[c00020000a637d90] [c0000000009f4540] local_pci_probe+0x68/0xf4
[c00020000a637e10] [c000000000169cdc] work_for_cpu_fn+0x38/0x54
[c00020000a637e40] [c00000000016ff24] process_one_work+0x1fc/0x4d4
[c00020000a637ef0] [c000000000170e3c] worker_thread+0x33c/0x504
[c00020000a637f90] [c00000000017d2fc] kthread+0x138/0x140
[c00020000a637fe0] [c00000000000de58] start_kernel_thread+0x14/0x18
Code: ebc1fff0 ebe1fff8 7c0803a6 4e800020 60000000 60000000 60420000 
3d220000 e9291800 e9290000 386903cc 7c0004ac <8bc903cc> 0c1e0000 
4c00012c 57c9063e
---[ end trace 0000000000000000 ]---

note: kworker/32:1[453] exited with irqs disabled

The faulting line is

    outb(inb(VGA_MIS_R), VGA_MIS_W);

in drivers/gpu/drm/i915/display/intel_vga.c

The 0x3cc offset is VGA_MIS_R, and R9 points to c00a000000000000, where 
the I/O ports are mapped -- however the legacy ports don't seem to be 
active if the card was never initialized at boot, which it isn't, 
because the BMC's VGA emulation is preferred.

Commenting out the call to intel_vga_reset_io_mem solves the problem, 
and I get wonderful 1080p60 output -- but obviously that is not a 
generic solution.

   Simon

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