Re: [BUG] BUG: kernel NULL pointer dereference at ttm_device_init+0xb4

[Steven Rostedt]

On Mon, 22 Jan 2024 19:29:41 -0500
"Bhardwaj, Rajneesh" <rajneesh.bhardwaj@xxxxxxx> wrote:

> 
> In one of my previous revisions of this patch when I was experimenting, 
> I used something like below. Wonder if that could work in your case 
> and/or in general.
> 
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c 
> b/drivers/gpu/drm/ttm/ttm_device.c
> 
> index 43e27ab77f95..4c3902b94be4 100644
> 
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> 
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> 
> @@ -195,6 +195,7 @@ int ttm_device_init(struct ttm_device *bdev, struct 
> ttm_device_funcs *funcs,
> 
> bool use_dma_alloc, bool use_dma32){
> 
> struct ttm_global *glob = &ttm_glob;
> 
> +bool node_has_cpu = false;
> 
> int ret;
> 
> if (WARN_ON(vma_manager == NULL))
> 
> @@ -213,7 +214,12 @@ int ttm_device_init(struct ttm_device *bdev, struct 
> ttm_device_funcs *funcs,
> 
> bdev->funcs = funcs;
> 
> ttm_sys_man_init(bdev);
> 
> -ttm_pool_init(&bdev->pool, dev, NUMA_NO_NODE, use_dma_alloc, use_dma32);
> 
> +
> 
> +node_has_cpu = node_state(dev->numa_node, N_CPU);

Considering that qxl_ttm_init() passes in dev = NULL, the above would blow
up just the same.

-- Steve


> 
> +if (node_has_cpu)
> 
> +ttm_pool_init(&bdev->pool, dev, dev->numa_node, use_dma_alloc, use_dma32);
> 
> +else
> 
> +ttm_pool_init(&bdev->pool, dev, NUMA_NO_NODE, use_dma_alloc,
> 
> +use_dma32);
> 
> bdev->vma_manager = vma_manager;
> 
> spin_lock_init(&bdev->lru_lock);
> 
> 
> >
> > -- Steve