[PATCH 3/4] drm/xe: Restore userspace LRC BOs early on resume

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

When GuC registers a context (REGISTER_CONTEXT G2H action), the LRC
buffer object must already be present in VRAM with valid content.
Userspace LRC BOs currently carry XE_BO_FLAG_PINNED_LATE_RESTORE, which
defers their restore to xe_bo_restore_late() — a blitter copy that runs
after xe_gt_resume().  However, xe_gt_resume() itself calls
xe_guc_submit_start(), which drives guc_exec_queue_start() ->
xe_sched_resubmit_jobs() -> guc_exec_queue_run_job() ->
register_exec_queue(), all before xe_bo_restore_late() has had a chance
to repopulate the BO.  The result is that GuC reads LRC state from
uninitialised VRAM and raises an exception.

Fix this by dropping XE_BO_FLAG_PINNED_LATE_RESTORE from the userspace
LRC BO flags.  Without that flag, the BO lands in the
pinned.early.kernel_bo_present list and is restored by
xe_bo_restore_early() via CPU/BAR copy before xe_gt_resume() is entered.
By the time any context registration fires the LRC VRAM is valid.

xe_bo_create_pin_map_novm() already adds XE_BO_FLAG_NEEDS_CPU_ACCESS and
XE_BO_FLAG_PINNED, satisfying the requirements of the CPU copy path.
Dropping XE_BO_FLAG_PINNED_LATE_RESTORE also makes force_contiguous()
return true for these BOs (PINNED without LATE_RESTORE), which is already
required for the GGTT mapping they carry.

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/xe/xe_lrc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
index a4292a11391d..c9ea5a3e5365 100644
--- a/drivers/gpu/drm/xe/xe_lrc.c
+++ b/drivers/gpu/drm/xe/xe_lrc.c
@@ -1661,7 +1661,7 @@ static int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe, struct xe_v
 		   XE_BO_FLAG_GGTT_INVALIDATE;
 
 	if ((vm && vm->xef) || init_flags & XE_LRC_CREATE_USER_CTX) /* userspace */
-		bo_flags |= XE_BO_FLAG_PINNED_LATE_RESTORE | XE_BO_FLAG_FORCE_USER_VRAM;
+		bo_flags |= XE_BO_FLAG_FORCE_USER_VRAM;
 
 	bo = xe_bo_create_pin_map_novm(xe, tile, bo_size,
 				       ttm_bo_type_kernel,
-- 
2.54.0