Looks good to me. One cosmetic comment inline. With that fixed this 
patch is Reviewed-by:  Felix Kuehling <felix.kuehl...@amd.com>

On 2019-06-14 12:51 p.m., StDenis, Tom wrote:
> On 32-bit hosts mem->num_pages is 32-bits and can overflow
> when shifted.  Add a cast to avoid this.
>
> Signed-off-by: Tom St Denis <tom.stde...@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c 
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index c963ad86072e..31895d3c33de 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -279,14 +279,16 @@ static int amdgpu_vram_mgr_new(struct 
> ttm_mem_type_manager *man,
>       uint64_t vis_usage = 0;
>       unsigned i;
>       int r;
> +     uint64_t mem_bytes;

Christian likes the "upside-down christmas tree" to help readability of 
local variable declarations.


>   
>       lpfn = place->lpfn;
>       if (!lpfn)
>               lpfn = man->size;
>   
>       /* bail out quickly if there's likely not enough VRAM for this BO */
> -     if (atomic64_add_return(mem->num_pages << PAGE_SHIFT, &mgr->usage) > 
> adev->gmc.mc_vram_size) {
> -             atomic64_sub(mem->num_pages << PAGE_SHIFT, &mgr->usage);
> +     mem_bytes = (u64)mem->num_pages << PAGE_SHIFT;
> +     if (atomic64_add_return(mem_bytes, &mgr->usage) > 
> adev->gmc.mc_vram_size) {
> +             atomic64_sub(mem_bytes, &mgr->usage);
>               mem->mm_node = NULL;
>               return 0;
>       }
> @@ -308,7 +310,7 @@ static int amdgpu_vram_mgr_new(struct 
> ttm_mem_type_manager *man,
>       nodes = kvmalloc_array((uint32_t)num_nodes, sizeof(*nodes),
>                              GFP_KERNEL | __GFP_ZERO);
>       if (!nodes) {
> -             atomic64_sub(mem->num_pages << PAGE_SHIFT, &mgr->usage);
> +             atomic64_sub(mem_bytes, &mgr->usage);
>               return -ENOMEM;
>       }
>   
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