drm/xe/guc: Dead CT helper

drm/xe/guc: Dead CT helper

Add a worker function helper for asynchronously dumping state when an
internal/fatal error is detected in CT processing. Being asynchronous
is required to avoid deadlocks and scheduling-while-atomic or
process-stalled-for-too-long issues. Also check for a bunch more error
conditions and improve the handling of some existing checks.

v2: Use compile time CONFIG check for new (but not directly CT_DEAD
related) checks and use unsigned int for a bitmask, rename
CT_DEAD_RESET to CT_DEAD_REARM and add some explaining comments,
rename 'hxg' macro parameter to 'ctb' - review feedback from Michal W.
Drop CT_DEAD_ALIVE as no need for a bitfield define to just set the
entire mask to zero.
v3: Fix kerneldoc
v4: Nullify some floating pointers after free.
v5: Add section headings and device info to make the state dump look
more like a devcoredump to allow parsing by the same tools (eventual
aim is to just call the devcoredump code itself, but that currently
requires an xe_sched_job, which is not available in the CT code).
v6: Fix potential for leaking snapshots with concurrent error
conditions (review feedback from Julia F).
v7: Don't complain about unexpected G2H messages yet because there is
a known issue causing them. Fix bit shift bug with v6 change. Add GT
id to fake coredump headers and use puts instead of printf.
v8: Disable the head mis-match check in g2h_read because it is failing
on various discrete platforms due to unknown reasons.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Julia Filipchuk <julia.filipchuk@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003004611.2323493-9-John.C.Harrison@Intel.com