[PATCH] drm/amdgpu/userq: lock and validate wptr BOs before reading their GPU offset on restore

amdgpu_userq_vm_validate_and_restore_queue() reads each queue's wptr BO
GPU offset via amdgpu_bo_gpu_offset() after only calling
amdgpu_ttm_alloc_gart() on it. But the wptr BOs are not part of this VM
(their reservation object is their own, not vm->root), so neither
amdgpu_vm_validate() nor amdgpu_userq_bo_validate() (which only handles
the VM's evicted list) covers them. As a result a wptr BO can still be in
TTM_PL_SYSTEM and unreserved when its offset is read, tripping the
amdgpu_bo_gpu_offset() sanity checks from the restore worker:

  ------------[ cut here ]------------
  WARNING: amdgpu_object.c:1486 at amdgpu_bo_gpu_offset+0x75/0xa0 [amdgpu], CPU#3: kworker/3:1/116
  Workqueue: events amdgpu_userq_restore_worker [amdgpu]
  RIP: 0010:amdgpu_bo_gpu_offset+0x75/0xa0 [amdgpu]
  Call Trace:
   <TASK>
   amdgpu_userq_vm_validate_and_restore_queue+0x629/0x960 [amdgpu]
   amdgpu_userq_restore_worker+0xa6/0x180 [amdgpu]
   process_scheduled_works+0xa6/0x460
   worker_thread+0x13c/0x290
   kthread+0xfb/0x140
   ret_from_fork+0x1b6/0x2b0
   ret_from_fork_asm+0x1a/0x30
   </TASK>
  ---[ end trace 0000000000000000 ]---
  ------------[ cut here ]------------
  WARNING: amdgpu_object.c:1485 at amdgpu_bo_gpu_offset+0x9a/0xa0 [amdgpu], CPU#2: kworker/2:1/127
  Workqueue: events amdgpu_userq_restore_worker [amdgpu]
  RIP: 0010:amdgpu_bo_gpu_offset+0x9a/0xa0 [amdgpu]

amdgpu_ttm_alloc_gart() only creates the GART mapping; it does not migrate
the BO out of system memory, so the offset read is bogus (the queue would
resume with a wrong wptr address).

Lock each wptr BO into the drm_exec context and validate it into GTT
inside the drm_exec_until_all_locked() block, mirroring what the create
path (mes_userq_create_wptr_mapping) already does, so that the offset read
later is safe and correct.

Signed-off-by: Jesse Zhang <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 26 +++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 17cc48d87c4d..59aa4802c111 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -1054,6 +1054,32 @@ amdgpu_userq_vm_validate_and_restore_queue(struct amdgpu_userq_mgr *uq_mgr)
 		drm_exec_retry_on_contention(&exec);
 		if (unlikely(ret))
 			goto unlock_all;
+
+		/*
+		 * The per-queue wptr BOs are not part of this VM (their resv is
+		 * their own, not vm->root), so the validation above does not
+		 * cover them. Lock and validate each into GTT here so that
+		 * reading its GPU offset below is safe - matching what the
+		 * create path (mes_userq_create_wptr_mapping) does.
+		 */
+		xa_for_each(&uq_mgr->userq_xa, tmp_key, queue) {
+			struct ttm_operation_ctx wptr_ctx = { false, false };
+
+			bo = queue->wptr_obj.obj;
+			if (!bo)
+				continue;
+
+			ret = drm_exec_prepare_obj(&exec, &bo->tbo.base,
+						   TTM_NUM_MOVE_FENCES + 1);
+			drm_exec_retry_on_contention(&exec);
+			if (unlikely(ret))
+				goto unlock_all;
+
+			amdgpu_bo_placement_from_domain(bo, bo->allowed_domains);
+			ret = ttm_bo_validate(&bo->tbo, &bo->placement, &wptr_ctx);
+			if (unlikely(ret))
+				goto unlock_all;
+		}
 	}
 
 	if (invalidated) {
-- 
2.49.0