fix(cuda.core): declare cdef attrs for system event wrappers and decode packed gpu_id

[rluo8]

Description

Two issues were found when adding coverage tests (internal bug 6595639):

1. Missing cdef attributes on SystemEvent, SystemEvents, EventData, and DeviceAttributes. These are Cython cdef class types (no __dict__), so undeclared self._event_data / self._attributes assignments raise AttributeError. RegisteredSystemEvents.wait() therefore crashes as soon as a real bind/unbind event arrives.

2. SystemEvent.device type mismatch. NVML's packed int gpu_id (domain[31:16] | bus[15:8] | device[7:0]), which requires an NVML-style PCI bus ID string (NVML_DEVICE_PCI_BUS_ID_FMT). Decode at the call site via _pci_bus_id_from_gpu_id.

Adds regression tests for construction, packing decode, and end-to-end SystemEvent.device resolution against live pci_info.

Verification:

• B10: new regression tests 8 passed; live unbind of 0000:c1:00.0
  yields SystemEvents with gpu_id=0xC100 → 00000000:C1:00.0, and
  post-rebind SystemEvent.device resolves correctly
• A100 MIG: DeviceAttributes cdef fix verified
• System Event register/wait remains Linux-only (Windows/WSL/WOA skip)

[rluo8]

Hi @mdboom , this issue is about system event. Could you please help review it?
Thanks!

[github-actions]

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[mdboom]

What is the root issue this is trying to solve?

This is making these objects mutable and they definitely shouldn't be -- their intention is to return values from the NVML API, not to set things on them.

The gpu_id / pci_id bridge in _system_events.pyx added here makes sense, though.

[rluo8]

Hi @mdboom , thanks for the review. I understand your concern. The root issue is that constructing SystemEvent / SystemEvents / EventData / DeviceAttributes throws exception: these are Cython cdef class types with no dict, so undeclared self._event_data / self._attributes in init raise AttributeError.

This is the reproduce script:

from cuda.bindings import nvml
from cuda.core.system._system_events import SystemEvents

ed = nvml.SystemEventData_v1(1)
ed.event_type = nvml.SystemEventType.GPU_DRIVER_UNBIND
ed.gpu_id = 0xC100
SystemEvents(ed) 

Output:

   SystemEvents(ed)  # main → AttributeError: no '_event_data' / no __dict__
    ~~~~~~~~~~~~^^^^
  File "cuda/core/system/_system_events.pyx", line 60, in cuda.core.system._system_events.SystemEvents.__init__
AttributeError: 'cuda.core.system._system_events.SystemEvents' object has no attribute '_event_data' and no __dict__ for setting new attributes

After the fix, it doesn't make the public API mutable, the cdef field is not visible from Python.
Test script:

from cuda.bindings import nvml
from cuda.core.system._system_events import SystemEvent

ed = nvml.SystemEventData_v1(1)
ed.event_type = nvml.SystemEventType.GPU_DRIVER_BIND
ed.gpu_id = 0xC100
event = SystemEvent(ed)
print("constructed OK:", event.event_type, hex(event.gpu_id))

try:
    event.event_type = "BIND"
except Exception as err:
    print(repr(err))

try:
    print(event._event_data)
except Exception as err:
    print(repr(err))

Output:

constructed OK: bind 0xc100
AttributeError("attribute 'event_type' of '...SystemEvent' objects is not writable")
AttributeError("'...SystemEvent' object has no attribute '_event_data'")

This looks similar to Cython’s guidance about cdef class AttributeErrors : https://docs.cython.org/en/stable/src/userguide/troubleshooting.html
AttributeErrors can also happen when writing into a cdef class, commonly in init:

cdef class Company:
    def __init__(self, staff):
        self.staff = staff  # AttributeError!

Unlike a regular class, cdef class has a fixed list of attributes that you can write to and you need to declare them explicitly. For example:

cdef class Company:
   cdef list staff
   # ...

Thanks!