Re: [PATCH] drm/ttm: fix error handling in ttm_bo_handle_move_mem()

Sending the first message didn't worked, so let's try again.

Am 16.06.21 um 08:30 schrieb Dan Carpenter:

There are three bugs here:

1. We need to call unpopulate() if ttm_tt_populate() succeeds.
2. The "new_man = ttm_manager_type(bdev, bo->mem.mem_type);" assignment was wrong and it was really assigning "new_mem = old_mem;". There is no need for this assignment anyway as we already have the value for "new_mem".
3. The (!new_man->use_tt) condition is reversed.

Fixes: ba4e7d973dd0 ("drm: Add the TTM GPU memory manager subsystem.") Signed-off-by: Dan Carpenter dan.carpenter@oracle.com

---

This is from reading the code and I can't swear that I have understood it correctly. My nouveau driver is currently unusable and this patch has not helped. But hopefully if I fix enough bugs eventually it will start to work.

Well NAK, the code previously looked quite well and you are breaking it now.

What's the problem with nouveau?

drivers/gpu/drm/ttm/ttm_bo.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index ebcffe794adb..72dde093f754 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -180,12 +180,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo, */ ret = ttm_tt_create(bo, old_man->use_tt); if (ret)

• 	goto out_err;
  

• 	return ret;
  
  

  if (mem->mem_type != TTM_PL_SYSTEM) { ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx); if (ret)

• 		goto out_err;
  

• 		goto err_destroy;
  

  } }

@@ -193,15 +193,17 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo, if (ret) { if (ret == -EMULTIHOP) return ret;

• goto out_err;
  

• goto err_unpopulate;
  

  }

  ctx->bytes_moved += bo->base.size; return 0;

-out_err:

• new_man = ttm_manager_type(bdev, bo->mem.mem_type);

This here switches new and old manager. E.g. the new_man is now pointing to the existing resource manager.

• if (!new_man->use_tt)

So we should destroy the TT object only if the old manager is not using one.

+err_unpopulate:

• if (new_man->use_tt)

• ttm_tt_unpopulate(bo->bdev, bo->ttm);
  

Unpopulate is not necessary, destroying is sufficient.

Christian.

+err_destroy:

• if (new_man->use_tt) ttm_bo_tt_destroy(bo);

  return ret;