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Date: Mon, 22 Jan 2024 19:34:53 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: "Bhardwaj, Rajneesh" <rajneesh.bhardwaj@amd.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Linus Torvalds
 <torvalds@linux-foundation.org>, Felix Kuehling <Felix.Kuehling@amd.com>,
 Christian =?UTF-8?B?S8O2bmln?= <christian.koenig@amd.com>,
 dri-devel@lists.freedesktop.org
Subject: Re: [BUG] BUG: kernel NULL pointer dereference at
 ttm_device_init+0xb4
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	<918ddc13-1cf8-4199-b5be-5719a023de42@amd.com>
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On Mon, 22 Jan 2024 19:29:41 -0500
"Bhardwaj, Rajneesh" <rajneesh.bhardwaj@amd.com> 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