drm/xe/gt_throttle: Avoid TOCTOU when monitoring reasons

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It's currently not possible to safely monitor if there's throttling
happening and what are the reasons. The approach of reading the status
and then reading the reasons is not reliable as by the time sysadmin
reads the reason, the throttling could not be happening anymore.

Previous tentative to fix that[1] was breaking the ABI and potentially
sysadmin's scripts. This takes a different approach of adding and
documenting the additional attribute. It's still valuable, though
redundant, to provide the simpler 0/1 interface.

In order to avoid userspace knowledge on the bitmask meaning and to be
able to maintain the kernel side in sync with possible changes in
future, just walk the attribute group and check what are the masks that
match the value read.

[1] https://lore.kernel.org/intel-xe/20241025092238.167042-1-raag.jadav@intel.com/

Cc: Raag Jadav <raag.jadav@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Link: https://patch.msgid.link/20251104-gt-throttle-cri-v5-1-4948b060bbfd@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

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This commit is contained in:

Lucas De Marchi 2025-11-04 14:20:51 -08:00

parent 424e2cce07

commit 83ccde67a3

1 changed files with 56 additions and 2 deletions

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drivers/gpu/drm/xe/xe_gt_throttle.c

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