Re: [PATCH AUTOSEL 5.10 13/22] drm/amdgpu: install stub fence into potential unused fence pointers

[Chia-I Wu]

On Sun, Jul 23, 2023 at 6:24 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:
>
> From: Lang Yu <Lang.Yu@xxxxxxx>
>
> [ Upstream commit 187916e6ed9d0c3b3abc27429f7a5f8c936bd1f0 ]
>
> When using cpu to update page tables, vm update fences are unused.
> Install stub fence into these fence pointers instead of NULL
> to avoid NULL dereference when calling dma_fence_wait() on them.
>
> Suggested-by: Christian König <christian.koenig@xxxxxxx>
> Signed-off-by: Lang Yu <Lang.Yu@xxxxxxx>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

We start getting this warning spew on chromeos, likely from
dma_fence_is_later because the stub fence is on a different timeline:

[  273.334767] WARNING: CPU: 1 PID: 13383 at
include/linux/dma-fence.h:478 amdgpu_sync_keep_later+0x95/0xbd
[  273.334769] Modules linked in: snd_seq_dummy snd_seq snd_seq_device
bridge stp llc tun vhost_vsock vhost vhost_iotlb
vmw_vsock_virtio_transport_common vsock 8021q veth lzo_rle
lzo_compress zram uinput snd_acp_sof_mach snd_acp_mach snd_soc_dmic
xt_cgroup rfcomm xt_MASQUERADE cmac algif_hash algif_skcipher af_alg
btusb btrtl btintel btbcm rtw89_8852ae rtw89_pci rtw89_8852a
rtw89_core snd_sof_amd_renoir snd_sof_xtensa_dsp snd_sof_amd_acp
snd_acp_pci snd_acp_config snd_soc_acpi snd_pci_acp3x snd_sof_pci
snd_sof snd_hda_codec_hdmi snd_sof_utils snd_hda_intel mac80211
snd_intel_dspcfg snd_hda_codec cros_ec_typec snd_hwdep roles
snd_hda_core typec snd_soc_rt5682s snd_soc_rt1019 snd_soc_rl6231
ip6table_nat i2c_piix4 fuse bluetooth ecdh_generic ecc cfg80211
iio_trig_sysfs cros_ec_lid_angle cros_ec_sensors cros_ec_sensors_core
industrialio_triggered_buffer kfifo_buf industrialio cros_ec_sensorhub
r8153_ecm cdc_ether usbnet r8152 mii uvcvideo videobuf2_vmalloc
videobuf2_memops videobuf2_v4l2
[  273.334795]  videobuf2_common joydev
[  273.334799] CPU: 1 PID: 13383 Comm: chrome:cs0 Tainted: G        W
       5.10.192-23384-g3d3f0f0c5e4f #1
fe1e7e3b7510aa7b8e01701478119255f825a36f
[  273.334800] Hardware name: Google Dewatt/Dewatt, BIOS
Google_Dewatt.14500.347.0 03/30/2023
[  273.334802] RIP: 0010:amdgpu_sync_keep_later+0x95/0xbd
[  273.334804] Code: 00 00 b8 01 00 00 00 f0 0f c1 43 38 85 c0 74 26
8d 48 01 09 c1 78 24 49 89 1e 5b 41 5e 5d c3 cc cc cc cc e8 4a 94 ac
ff eb ce <0f> 0b 49 8b 06 48 85 c0 75 af eb c2 be 02 00 00 00 48 8d 7b
38 e8
[  273.334805] RSP: 0018:ffffb222c1817b50 EFLAGS: 00010293
[  273.334807] RAX: ffffffff89bfc838 RBX: ffff8aa425e9ed00 RCX: 0000000000000000
[  273.334808] RDX: ffff8aa426156a98 RSI: ffff8aa425e9ed00 RDI: ffff8aa432518918
[  273.334810] RBP: ffffb222c1817b60 R08: ffff8aa43ca6c0a0 R09: ffff8aa33af3c9a0
[  273.334811] R10: fffffcf8c5986600 R11: ffffffff87a00fce R12: 0000000000000098
[  273.334812] R13: 00000000005e2a00 R14: ffff8aa432518918 R15: 0000000000000000
[  273.334814] FS:  00007e70f8694640(0000) GS:ffff8aa4e6080000(0000)
knlGS:0000000000000000
[  273.334816] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  273.334817] CR2: 00007e70ea049020 CR3: 0000000178e6e000 CR4: 0000000000750ee0
[  273.334818] PKRU: 55555554
[  273.334819] Call Trace:
[  273.334822]  ? __warn+0xa3/0x131
[  273.334824]  ? amdgpu_sync_keep_later+0x95/0xbd
[  273.334826]  ? report_bug+0x97/0xfa
[  273.334829]  ? handle_bug+0x41/0x66
[  273.334832]  ? exc_invalid_op+0x1b/0x72
[  273.334835]  ? asm_exc_invalid_op+0x12/0x20
[  273.334837]  ? native_sched_clock+0x9a/0x9a
[  273.334840]  ? amdgpu_sync_keep_later+0x95/0xbd
[  273.334843]  amdgpu_sync_vm_fence+0x23/0x39
[  273.334846]  amdgpu_cs_ioctl+0x1782/0x1e56
[  273.334851]  ? amdgpu_cs_report_moved_bytes+0x5f/0x5f
[  273.334854]  drm_ioctl_kernel+0xdf/0x150
[  273.334858]  drm_ioctl+0x1f5/0x3d2
[  273.334928]  ? amdgpu_cs_report_moved_bytes+0x5f/0x5f
[  273.334932]  amdgpu_drm_ioctl+0x49/0x81
[  273.334935]  __x64_sys_ioctl+0x7d/0xc8
[  273.334937]  do_syscall_64+0x42/0x54
[  273.334939]  entry_SYSCALL_64_after_hwframe+0x4a/0xaf
[  273.334941] RIP: 0033:0x7e70ff797649
[  273.334943] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10
c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00
00 0f 05 <41> 89 c0 3d 00 f0 ff ff 77 1d 48 8b 45 c8 64 48 2b 04 25 28
00 00
[  273.334945] RSP: 002b:00007e70f8693170 EFLAGS: 00000246 ORIG_RAX:
0000000000000010
[  273.334947] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007e70ff797649
[  273.334948] RDX: 00007e70f8693248 RSI: 00000000c0186444 RDI: 0000000000000013
[  273.334950] RBP: 00007e70f86931c0 R08: 00007e70f8693350 R09: 00007e70f8693340
[  273.334951] R10: 000000000000000a R11: 0000000000000246 R12: 00000000c0186444
[  273.334952] R13: 00007e70f8693380 R14: 00007e70f8693248 R15: 0000000000000013
[  273.334954] ---[ end trace fc066a0fcea39e8c ]---