Actually, GPU had been working for a while and stopped working after some kernel + driver update.
➜ tmp git:(master) ✗ cat /proc/driver/nvidia/gpus/0000\:01\:00.0/information
Model: Unknown
IRQ: 16
GPU UUID: GPU-????????-????-????-????-????????????
Video BIOS: ??.??.??.??.??
Bus Type: PCIe
DMA Size: 47 bits
DMA Mask: 0x7fffffffffff
Bus Location: 0000:01:00.0
Device Minor: 0
Blacklisted: No
[ 1321.722194] NVRM: RmInitAdapter failed! (0x26:0xffff:1106)
[ 1321.722239] NVRM: rm_init_adapter failed for device bearing minor number 0
This error looks suspicious to me:
[ 396.458] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied
[ 396.459] (--) PCI:*(1@0:0:0) 10de:1c8c:1028:087c rev 161, Mem @ 0xec000000/16777216, 0xc0000000/268435456, 0xd0000000/33554432, I/O @ 0x00003000/128, BIOS @ 0x????????/524288