drm/xe: Fix tlb invalidation when wedging

If GuC fails to load, the driver wedges, but in the process it tries to
do stuff that may not be initialized yet. This moves the
xe_gt_tlb_invalidation_init() to be done earlier: as its own doc says,
it's a software-only initialization and should had been named with the
_early() suffix.

Move it to be called by xe_gt_init_early(), so the locks and seqno are
initialized, avoiding a NULL ptr deref when wedging:

	xe 0000:03:00.0: [drm] *ERROR* GT0: load failed: status: Reset = 0, BootROM = 0x50, UKernel = 0x00, MIA = 0x00, Auth = 0x01
	xe 0000:03:00.0: [drm] *ERROR* GT0: firmware signature verification failed
	xe 0000:03:00.0: [drm] *ERROR* CRITICAL: Xe has declared device 0000:03:00.0 as wedged.
	...
	BUG: kernel NULL pointer dereference, address: 0000000000000000
	#PF: supervisor read access in kernel mode
	#PF: error_code(0x0000) - not-present page
	PGD 0 P4D 0
	Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
	CPU: 9 UID: 0 PID: 3908 Comm: modprobe Tainted: G     U  W          6.13.0-rc4-xe+ #3
	Tainted: [U]=USER, [W]=WARN
	Hardware name: Intel Corporation Alder Lake Client Platform/AlderLake-S ADP-S DDR5 UDIMM CRB, BIOS ADLSFWI1.R00.3275.A00.2207010640 07/01/2022
	RIP: 0010:xe_gt_tlb_invalidation_reset+0x75/0x110 [xe]

This can be easily triggered by poking the GuC binary to force a
signature failure. There will still be an extra message,

	xe 0000:03:00.0: [drm] *ERROR* GT0: GuC mmio request 0x4100: no reply 0x4100

but that's better than a NULL ptr deref.

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3956
Fixes: 7dbe8af ("drm/xe: Wedge the entire device")
Reviewed-by: Matthew Brost <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>

Author: lucasdemarchi

drivers/gpu/drm/xe/xe_gt.c

@@ -387,6 +387,10 @@ int xe_gt_init_early(struct xe_gt *gt)
 	xe_force_wake_init_gt(gt, gt_to_fw(gt));
 	spin_lock_init(&gt->global_invl_lock);
 
+	err = xe_gt_tlb_invalidation_init_early(gt);
+	if (err)
+		return err;
+
 	return 0;
 }
 
@@ -588,10 +592,6 @@ int xe_gt_init(struct xe_gt *gt)
 		xe_hw_fence_irq_init(&gt->fence_irq[i]);
 	}
 
-	err = xe_gt_tlb_invalidation_init(gt);
-	if (err)
-		return err;
-
 	err = xe_gt_pagefault_init(gt);
 	if (err)
 		return err;

drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c

@@ -106,15 +106,15 @@ static void xe_gt_tlb_fence_timeout(struct work_struct *work)
 }
 
 /**
- * xe_gt_tlb_invalidation_init - Initialize GT TLB invalidation state
+ * xe_gt_tlb_invalidation_init_early - Initialize GT TLB invalidation state
  * @gt: graphics tile
  *
  * Initialize GT TLB invalidation state, purely software initialization, should
  * be called once during driver load.
  *
  * Return: 0 on success, negative error code on error.
  */
-int xe_gt_tlb_invalidation_init(struct xe_gt *gt)
+int xe_gt_tlb_invalidation_init_early(struct xe_gt *gt)
 {
 	gt->tlb_invalidation.seqno = 1;
 	INIT_LIST_HEAD(&gt->tlb_invalidation.pending_fences);

drivers/gpu/drm/xe/xe_gt_tlb_invalidation.h

@@ -14,7 +14,8 @@ struct xe_gt;
 struct xe_guc;
 struct xe_vma;
 
-int xe_gt_tlb_invalidation_init(struct xe_gt *gt);
+int xe_gt_tlb_invalidation_init_early(struct xe_gt *gt);
+
 void xe_gt_tlb_invalidation_reset(struct xe_gt *gt);
 int xe_gt_tlb_invalidation_ggtt(struct xe_gt *gt);
 int xe_gt_tlb_invalidation_vma(struct xe_gt *gt,