[PATCH] drm/amd/amdgpu: cast mem->num_pages to 64-bits when shifting

[Kuehling, Felix]

On 2019-06-17 3:28 p.m., Christian König wrote:
> Am 17.06.19 um 21:15 schrieb Kuehling, Felix:
>> Looks good to me. One cosmetic comment inline. With that fixed this
>> patch is Reviewed-by:  Felix Kuehling <Felix.Kuehling at 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.stdenis at 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.
>
> Ah, yeah. Thanks for the note.
>
> I actually don't care about that much, but I always get rejects from 
> upstream subsystem maintainers if I don't do this.
>
> It's most likely not even documented somewhere,

Right. The fact that I even noticed it probably means that I have a mild 
case of OCD myself. If it was a strict requirement, it should be caught 
by checkpatch.pl.

Cheers,
   Felix


> Christian.
>
>>
>>
>>>           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;
>>>        }
>> _______________________________________________
>> amd-gfx mailing list
>> amd-gfx at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>