[RFC PATCH RESEND 0/2] Xe driver asynchronous notification mechanism

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

There is a need to inform user-space clients when a rebind worker
has ran out of memory so that it can react, adjust its working-set
and restart the job. This patch series aims to start a discussion
about the bet way to accomplish this.

The series builds on the core "general notification mechanism" or
"watch_queue", and attaches a watch queue to each xe drm file.

The watch_queue is extremely flexible and allows filtering out
events of interest at the kernel level. There can be multiple
listeners.

Another approach would be to use drm events, but then there
could only be one listener per open file and no filtering.
Otoh drm events would probably have the shortest delivery
latency.

Finally there is eventfd (man 2 eventfd) but doesn't appear to
allow carrying metadata.

Any feedback appreciated, also on method preference.

Patch 1 extende the watch_queue interface slightly,
Patch 2 implements delivery of a VM rebind worker error.

Note this is to be regarded as a POC at this time. No need for
a detailed review.

A user-space igt user is posted as an RFC here:

https://patchwork.freedesktop.org/series/162576/

RESEND:
- Widening the audience to solicit watch_queue feedback.

Thomas Hellström (2):
  watch_queue: Add a DRM_XE_NOTIFY watch type and export init_watch()
  drm/xe: Add watch_queue-based device event notification

 drivers/gpu/drm/xe/Kconfig           |   1 +
 drivers/gpu/drm/xe/Makefile          |   1 +
 drivers/gpu/drm/xe/xe_device.c       |   7 ++
 drivers/gpu/drm/xe/xe_device_types.h |   6 ++
 drivers/gpu/drm/xe/xe_vm.c           |   7 +-
 drivers/gpu/drm/xe/xe_vm_types.h     |   2 +
 drivers/gpu/drm/xe/xe_watch_queue.c  | 107 +++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_watch_queue.h  |  20 +++++
 include/uapi/drm/xe_drm.h            |  46 ++++++++++++
 include/uapi/drm/xe_drm_events.h     |  56 ++++++++++++++
 include/uapi/linux/watch_queue.h     |   3 +-
 kernel/watch_queue.c                 |  13 +++-
 12 files changed, 263 insertions(+), 6 deletions(-)
 create mode 100644 drivers/gpu/drm/xe/xe_watch_queue.c
 create mode 100644 drivers/gpu/drm/xe/xe_watch_queue.h
 create mode 100644 include/uapi/drm/xe_drm_events.h

-- 
2.53.0